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HP 6472C User's Manual

1. v MAINTENANCE nan 5 1 Introduction na 5 3 Test Equipment Required 5 5 Performance Test 5 7 Constant Voltage Tests 5 27 Constant Current Tests 5 35 Troubleshooting 5 40 Overall Troubleshooting Procedure 5 44 Amplifier Circuits Open Loop Troubleshooting 5 49 Firing Circuits Open Loop Troubleshooting 5 51 Crowbar Troubleshooting 5 54 Repair and Replacement 5 56 Air Filter 5 58 Hinged Front Panel 5 60 Printed Circuit Board co 5 62 Primary SCR and Diode Replacement amp 5 66 Location of Power Transformer Choke Output Capacitors and Secondary Rectifiers 5 12 5 68 Adjustment and Calibration 5 70 Meter Zero iii SAFETY SUMMARY The following general safety precautions must be observed during all phases of operation service and repair of this instru ment Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design manufacture and intended use of the instrument Hewlett Packard Company assumes no liability for the customer s failure to comply with these requirements BEFORE APPLYING POWER Verify that the product is set to match the available line voltage and the correct fuse is installed GROUND THE INSTRUMENT This product is a Safety Class 1 instrument provided with a protective earth terminal To minimize shock hazard the in strument chassis and cabinet must be con
2. Cover Capacitor Tray 5000 9454 Er 5000 6286 Tray 5000 9479 Er pone 6289 Ear Rack Mounting 2 5020 7062 5020 8037 lt Option 23 Front Panel Crowbar 5000 9382 5000 9324 lt Option n the for owing y not rrent panel tance d for MODEL VOLTAGE Maximum allowable terminal voltage before terminals are shorted 6464C 5y 61660 6y 6469C 8v 6472C 10V 6475C 17V 6477C 30V 6479C 30V 6483C hov On page 3 1 paragraph 3 2 change step c to read as follows to check out constant cur rent circuit first turn off supply and al low the output voltage to bleed down Then short circuit the output bus bars and rotate Voltage controls fully clockwise Turn on supply On page 3 2 paragraph 3 8 add the following sentence to the beginning of step b Turn off supply and allow the output voltage to leed dow Add this same sentence to para aph 3 10 step a paragraph 3 55 steps b and d and paragraph 5 32 step e In the replaceable parts list and on the schematic diagram change variable resistors ALR102 and A1R122 to 20K 1 2W HP P N 2100 0058 i CHANGE 8 One of two types of fans is used in this sup ply HP P N 3160 0240 or 3160 0285 The capiacitor C19 to be used with the fan depends on which fan is installed With fan 3160 0240 use 8uf 370Vrms capacitor HP P N 0160 4122 With fan 3160 0285 use 5uf 370Vrms capacitor HP
3. in cabinet performance check to verify proper instrument operation 2 7 INSTALLATION DATA 2 8 The instrument is shipped ready for operation It is necessary only to connect the instrument to a source of pow er and it is ready for operation 29 Location 2 10 This instrument is fan cooled Sufficient space should be allotted so that a free flow of cooling air can reach the sides of the instrument when it is in operation It should be used in an area where the ambient temperature does not ex ceed 50 C 2 11 Outline Diagram 2 12 Figure 2 1 illustrates the two basic outline shapes for power supplies of the SCR 10 Series a BA nce pe KES i a pa Taa eect we ia a A A n eae ts E i A MODELS 6464C 6466C AND 6469C aoe soe w 8 MODELS 6472C 6475C 6477C 6479C AND 6483C Figure 2 1 Outline Diagram zen 1p oa on Ela act 2e 213 Rack Mounting 2 14 To rack mount the unit Option 023 is installed at the factory The user receives the supply with rack ears attached to the side front of the unit The supply can then be mount ed in a standard 19 inch rack using standard mounting screws 2 15 INPUT POWER REQUIREMENTS 2 16 The input power is specified by the buyer in his ori ginal purchase contract using the appropriate option num ber Five input options are available Option 001 208Vac 002 230Vac 003 460Vac 031 3
4. The actual time required for the output voltage to decrease to a level set by the front panel control varies from approximately 6 seconds to about 200 seconds depending on the model number and the incremental change 3 13 Output Ranges Models 6466C and 6483C Only 3 14 Model 6466C can be operated in one of two output ranges while Model 6483C has three output ranges refer to Specification Table 1 1 for these units No range switch ing is required but the current and voltage requirements of the load should be predetermined to ensure that the ratings for a particular range will not be exceeded If a rating is ex ceeded one of the supply s internal protection circuits will be activated For example if the supply is operating in the high voltage low current range and the output current ex ceeds the rating for that range the overcurrent circuit will become activated and shut off the supply 3 15 Connecting Load 3 16 Each load should be connected to the power supply output terminals using separate pairs of connecting wires This will minimize mutual coupling effects between loads and will retain fuli advantage of the low output impedance of the power supply Each pair of connecting wires should be as short as possibie and twisted or shielded to reduce noise pickup If a shielded pair is used connect one end of the shield to ground at the power supply and leave the other end unconnected 3 17 If load considerations require tha
5. a battery may be charged at a constant current until the maximum charge voltage is reached at which poin the supply wil revert to constant voltage and continue to supply a trickle charge current sufficient to maintain full charge see Figure 3 10 Thus the charging operation can be unattended after property setting the charging rate and the maximum charge voltage and connecting the battery to the output terminals of the suppiy 3 55 The procedure for setting the charging rate and full charge voltage on SCR 10 Series power supplies is as fol lows a Turn both the VOLTAGE and CURRENT control fully counterclockwise CCW b Place a short circuit across the output terminals and rotate the VOLTAGE control fully clockwise CW c Rotate the CURRENT control to the desired charging rate as read on the front panel ammeter d Rotate VOLTAGE control fully CCW and remove the short circuit e Rotate the VOLTAGE control to the desired full charge voltage as read on either the front panel voltmeter 2 accuracy or a more precise voltage standard The unit may then be connected to the battery terminals positive ti positive and negative to negative 3 56 Protecticn diode CRp prevents a charged battery fro discharging into the supply if the supply is turned off AIG AIZ AIC An AIO AS AB alg 1 Ripa A TAPER Ep CHARGING E 1 k Ep BATTERY FULL CHARGE VOLTAGE Ig CONSTANT CHARGE CURRENT Ey B
6. agree with those on the title page of the manual Chan Sheets supplied with the manual or Manual Backdating Changes define the differences between your instrumen and the instrument described by this manual 1 14 ORDERING ADDITIONAL MANUALS 1 15 One manual is shipped with each power supply Ac tional manuals may be purchased from your local Hewlet Packard field office see list at rear of this manual for addr es Specify the model number serial number prefix and part number shown on the title page Table 1 1 Specifications INPUT 208 230 380 400 460Vac 10 Three Phase 57 to 63Hz 50A per phase 230Vac OUTPUT 0 64V 0 150A NOTES 1 and 2 LOAD REGULATION Constant Voltage Less than 0 05 plus 100mV for a load current change equal to the current rating of the supply Constant Current Less than 0 1 plus 0 154 for a load voltage change equal to the voltage rating of the supply LINE REGULATION Constant Voltage Less than 0 05 plus 100mV for any change within the input rating Constant Current Less than 0 1 plus 0 15A for any change within the input rating RIPPLE AND NOISE Constant Voltage Less than 160mVrms 2V p p de to 20MHz NOTE 2 TEMPERATURE RATINGS Operating O to 50 C Storage 40 to 750C TEMPERATURE COEFFICIENT Constant Voltage Less than 0 03 plus 4mV change in output per degree Centigrade change in ambient fol lowing 30 minutes warm up Constant Cu
7. form at the 12 4V reference level The reset signals are coupled to the ramp and base capacitors through diodes CR3 CR4 phase A CR13 CR14 phase B and CR23 CR24 phase C Reset starts during the negative transition of the reset waveform and the base and emitter capacitors require about 2msec to reach their starting voltages The capacitors remain at this point for about 5 6msec whereupon a new ac input cycle begins and the entire operation is re peated 440 Firing Angle Determination The firing angle of the SCR s determines the amount of ac power applied to the in put transformer and thus the amplitude of the de output An SCR that is fired at an early point in the input cycle pro vides a higher output than one that is fired later in the input cycle 4 41 Two types of inputs to the firing circuits control the time at which the firing pulses are generated The input having the greatest degree of contro is the main feedback loop input from the error amplifier As previously mention ed this input varies between 1V and 3V according to the output conditions A more positive feedback voltage in creases the steepness of the positive going ramp on the emit ters of each blocking oscillator and the SCR s are fired early in the input cyele The reverse is true for a more negative feedback voltage In this manner the feedback voltage cor rects for output changes due to variations in the load resist ance or line voltage 442 The
8. ple BE pela Figure 3 2 Normal Strapping Pattern 3 9 Constant Current 3 10 To select a constant current output proceed as fol lows a Short circuit output terminals and adjust CUR RENT controls for desired output current b Open output terminals and adjust VOLTAGE trols for maximum output voltage allowable voltage lim as determined by load conditions If a toad change cause the voltage limit to be exceeded the power supply will a matically cross over to constant voltage output at the pre voltage limit and the output current will drop proportior ately In setting the voltage limit allowance must be mad for high peak voltages which can cause unwanted crossov Refer to Paragraph 3 63 NOTE As indicated on the Specification Table 1 1 the supply may not meet ell specifications under tight load conditions These constraints are due to minimum operating thresh olds inherent in the SCR in the regulator However as shown on Table 1 1 the supply will operate satisfactorily if the supply delivers more than 30 of the rated output voltage Constant Voltage opera tion or rated output current Con stant Current operation Only 5 of rated output voltage or current is required provided that the supply is delivering more than 100 Watts to the load 3 11 No Load Operation 3 12 When the supply is operated without a load down programming speed is considerably slower than in normal loaded operation
9. 4 Remote Resistance Programming Constant Voltage Unity Gain 3 4 3 31 Voltage Programming Unity Gain Figure 3 4 Em ploy the strapping pattern shown in Figure 3 4 for voltage programming with unity gain In this mode the output vol age wilt vary in a 1 to 1 ratio with the programming voltage reference voltage and the load on the programming voltac source will not exceed 20 microamperes 3 32 To prevent the internal programming current from flowing to terminal A2 and into the external voltage source a jumper strap on P C Board A1 must be removed see Fig ure 7 1 for location of the jumper Be sure to reconnect this jumper before converting the unit to a different oper ating mode 3 33 The output voltage of this supply cannot be voltage programmed with gain unlike some of the other HP supplie 3 34 Remote Programming Constant Current 3 35 Either a resistance or a voltage source can be used to control the constant current output of the supply The CURRENT controls on the front panel are automatically disabled by the following procedures 3 36 Resistance Programming Figure 3 5 in this mode the output current varies at a rate determined by the con stant current programming coefficient given in Specifica tions Table 1 1 The programming coefficient is determine by the constant current programming current which is ad justed to within 2 at the factory If greater programming accuracy is required it may be achieved by
10. P N 0160 0585 CHANGE 9 In the replaceable parts list on page 6 10 under Main Frame Electrical change Fan BL to Fan Assembly B1 HP P N 3160 0498 and on page 6 12 change Bracket Fan B1 HP P N 5000 9321 to HP P N 5020 2684 TQ 1 der Rear Panel Assembly Electrical and o schematic diagram change the descriptic Fu F5 and F6 to Fuse can be 0 34 601 0 3154 609V ERRATA In the Operating and Service manual units with Option 040 add the foll note NOTE When calibrated for Option 040 units ma meet full output voltage or cw specification when used with the front potentiometer This is due to the resis tolerance of the potentiometer and programming coefficient accuracy require Option 040 SECTION GENERAL INFORMATION 1 1 DESCRIPTION 1 2 This power supply Figure 1 1 is completely transis torized and is suitable for high power applications which re quire a de source with a moderate degree of regulation The supply is a constant voltage constant current type that will furnish full rated output voltage at the maximum rated out put current or can be continuously adjusted throughout most of the output range The front panel CURRENT con trols can be used to establish the output current limit over load or short circuit when the supply is used as a constant voltage source and the VOLTAGE controls can be used to establish the voltage limit ceiling when the supply is used as a constant current source The sup
11. adjusting ATR2 as discussed in Paragraph 5 83 The output current of the supply when zero ohms is placed across the programming terminals may be set to exactly zero by adjusting A1 R28 as discussed in Paragraph 5 82 3 37 Use stable low noise low temperature coefficient less than 30ppm 0C programming resistors to maintain the power supply temperature coefficient and stability ARAB AR A AKAD AB AT AG AS fa S S A3 AZ AL BG el Rig o PROGRAMMING RESISTOR Figure 3 5 Remote Resistance Programming Constant Current specifications A switch may be used to set discrete values of output current A make before break type of switch should be used since the output current will exceed the maximum rating of the power supply if the switch contacts open during the switching interval CAUTION if the programming terminals A4 and A8 should open at any time during the remote re sistance programming mode the output current will rise to a value that may damage the load If in the particular programming configuration in use there is a chance that the terminals might become open it is suggested that a 1k8 resistor be connected across the programming terminals Like the programming resistor this resistor should be a low noise low temperature coeffi cient type Note that when this resistor is used the resistance value actually programming the supply is the parallel combination of the remote programming re
12. co ditions 4 80 Overcurrent Circuit Diodes CR50 through CR53 and capacitor C52 rectify and filter the phase B and C line voltage to provide a de voltage which is equivalent to the line current During normal conditions no overload the rectified voltage is not sufficiently positive to turn on uni junction transistor Q11 With Q11 off relay K1 is energize once power is applied to bridge rectifier CR54 CR57 through the LINE switch Closed contacts 8 and 12 of K then allow K2 to energize permitting application of the main three phase power to the unit 4 81 If the rms amplitude of the tine current rises above 40 of the input line rating Q11 turns on providing a posi tive pulse to transformer T6 This pulse fires an SCR CR58 connected across relay K1 With K1 deenergized the ac path to contactor K2 is broken deenergizing this relay C1 sup able vave to ists ier Ws ffer iin con aner ta and removing the ac power Notice that 2 phase power is still applied to the overload circuit keeping CR58 in conduc tion and illuminating the OVERCURRENT PROTECT lamp through closed contacts of K1 It requires approximately one second for the relays to deenergize and shut off power 4 82 Overload relay K1 is also deenergized if the crowbar circuit optional circuit is activated The pulse is applied to an additional winding of T6 to SCR CR58 The OVERCUR RENT PROTECT lamp will also be illuminated in this case together w
13. conditions Dur ing norma operation of the supply the early overcurrent protection circuit and or the constant current feedback loop will compensate for overcurrent problems before the over load circuit ever becomes activated However should a fail ure occur within these overcurrent protection circuits the overload circuit would then become activated deenergizing K2 and shutting off the supply 4 25 A thermal switch mounted on the SCR heat sink pro vides overtemperature protection by opening if the heat sink temperature rises to 2000 B0F 208Vac or 230Vac input or 1700 5 F 380Vac 400Vac or 460Vac input Opening the thermal switch deenergizes contactor K2 and removes the short across the TEMPERATURE lamp allow ing it to light 4 26 Reference Supply 4 27 The reference supply provides regulated bias voltages which are used by the internal circuitry throughout the main power supply All of the voltages shown are regulated except for the 24V 4 28 Overvoltage Crowbar Optional Circuit not available for Model 6464C 4 29 A built in overvoltage crowbar protection circuit Option 006 can be ordered with any power supply inthe ing or ing actor rap rns gof de al ings tter iger nd SCR 10 Series with the exception of Mode 6464C This cir cuit monitors the output voltage of the supply and fires an SCR if the output voltage exceeds a preset and adjustable threshold The condu
14. primary windings are also Ry located on the rear panel ing Figure 3 5 Remote Resistance Programm In paragraphs 4 18 and 4 24 change 40 to Constant Current 140 gray The standard colors for this instrument are now mint gray for front panel and olive me of for all other external surfaces Option X95 designates use of the former color sche olive light gray and blue gray Option A85 designates use of a light gray front panel with gray used for all other external surfaces New part numbers are shown below HP PART NO DESCRIPTION Front Panel Assembly Front Panel Lettered 06472 60004 06472 60013 0612 60005 lt al Cover Top 5000 9417 lt 5000 6292 Cover Side 2 5000 9418 lt 5000 6293 Bottom Front Panel 5000 9447 5000 6294 lt Cover Output Busbar 5000 9467 5000 6300 lt Cover Barrier Strip 5000 9457 Lam 5000 9320 Bottom Rear Panel 5000 9466 5000 6295 lt Panel Rear 5000 6282 5000 6283 lt Mounting Plate 5000 9465 5000 6284 lt Pan Bottom Left 5000 9480 lt 5000 6290 Bracket Heat Sink 5000 9481 lt 5000 9330 Post Corner Frame 2 5020 8446 lt 5020 8021 Bar Frame 2 5020 8448 lt 5020 8022 Tray Capacitor 5000 9453 lt 5000 6285
15. second input to the firing circuits consists of the phase B and phase C contro signals from the current balance circuit These signals correct for smail line to line variations in the three phase input currents To accomplish this the control signals are fed directly to base capacitors C14 and C24 in the phase B and C blocking oscillators If the line cur rents are all equal to each other the two control signals are at OV potential and do not affect the firing circuit If the line currents become unequal the phase B or phase C con trol signat swings momentarily positive or negative depend ing on the polarity of the original difference A control sig nal that momentarily swings negative at the base of the blocking oscillator allows the emitter ramp voltage to catch the base voltage earlier in the cycle thus increasing the SCR firing angle A positive going current balance control signal has the opposite effect 4 43 SCR Firing Circuit and Regulator Behavior at Low Outputs Each firing circuit and its associated SCR has a minimum operating threshold below which turn on of either 4 5 or both will not occur This threshold point varies and is determined by the inherent characteristics of both the firing circuit and the SCR of interest 4 44 When the supply is delivering medium and high output power each SCR conducts once during every ac input cycle of its associated phase However at low power outputs only two or even one SCR wi
16. 80Vac and 032 400V ac All of the optional line voltages may vary within 110 2 17 All ac input connections are made at the rear terminal block a power cord and connector are not supplied with the unit The user should ensure that the ac input wires are of the proper gauge For example the line current is 50 amperes maximum for a 230Vac input dictating that each conductor be at least number 8 gauge wire The safety ground wire should be the same gauge as the ac input wires to ensure that it does not open and create a safety hazard 2 18 The ac power source to this supply may be either delta or wye with isolated neutral The three phase input voltages must be balanced to within 8 of each other for the supply to operate However if the input fine voltages are unbalanced by more than 3 the unit may not meet the published rippie and noise specification although it will meet ail other specifications Moreover if the user s line im baiance exceeds 3 it is advisable to check the input line currents and adjust the current balance circuit if necessary refer to Paragraph 5 95 2 19 Any SCR regulated supply because of its inherent characteristics cannot tolerate a great degree of distortion in the input line voltage The amount of distortion that can be tolerated is not precisely defined but the supply should never be driven from the output of an inverter or a saturable reactor type of regulator where the nominally sinusoidal wa
17. ATTERY VOLTAGE AT WHICH CHARGE RATE WILL BEGIN TO TAPER WITH INSERTION OF Ry Em Ey k 6 AS AS 8 S A3 AZ Ai AC Tol Tala gt BATTERY Rye Figure 3 10 Battery Charging ts NOTE A large battery connected as a load presents a large capacitance across the output terminals This capacitance could cause the supply to oscil late particularly if remote sensing is employed To stabilize the supply potentiometer A1R48 may be readjusted increase resistance as out lined in Paragraph 5 88 If the maximum resist ance of R48 is not sufficient jumper R58 can be removed and an additional resistance sub stituted in series with the potentiometer 3 57 Taper Charge For charging lead acid cells the charg Ing current should be reduced when the battery is nearing completion of its charge This is accomplished by inserting a small resistance RT in series with one of the load leads from the supply to the battery which alters the normally rectangular charging plot in such a manner as to provide a taper charge for the last portion of the charge cycle The value of this resistance is the difference between the full charge voltage and the voltage at which the tapering is to start divided by the maximum charging current 3 58 Battery Discharging 3 59 Automatic constant current unattended discharging of a battery using the SCR 10 Series requires certain changes in the strapping configuration on the rear barrier st
18. B If a difference exists the differential amplifier produces an error signal which is proportional to this difference The remaining components in the feedback loop amplifiers firing circuit and SCR s function to main tain the drop across the current sampling resistors and hence the output current at a constant value 4 56 One input of the differential amplifier pin 1 is con nected to the supply s common point which is tied to the outbound side of the sampling resistors The other input of the differential amplifier pin 10 is connected to a sum ming point terminal A6 at the junction of the program ming resistors and the current pullout resistors R25 and R26 46 Changes in the output current due to load changes or changes in the voltage at the summing point due to manipr lation of the CURRENT controls produce a difference val age between the two inputs of the differential amplifier This difference voltage is amplified and appears at the out put of the differential amplifier pin 12 as an error voltag which ultimately varies the conduction of the SCR s 4 57 Error Amplifier 4 58 Operational amplifier stage U3 provides most of the feedback loop gain During normal operation U3 receives the feedback voltage at its non inverting input from either the constant voltage or constant current comparator via O gate diode CR23 or CR24 Diode CR23 is forward biased and CR24 reverse biased during constant voltage operation The r
19. SE C FIRING CIRCUITS CONSTANT VOLTAGE COMPARATOR TEMPERATURE OVERLOAD OVERCURRENT ECTION CURRENT CURRENT PROTECTION gine eee ee CROWBAR IOPTION 006 o DENOTES CONSTANT VOLTAGE FEEDBACK PATH DENCTES CONSTANT CURRENT FEEDBACK PATH Figure 4 1 Overall Block Diagram 4 1 OVERALL BLOCK DIAGRAM Constant Current comparators as a feedback loop The teed DISCUSSION back loop determines the firing time of the SCR s so that a regulated ac input voltage is applied to the primary of the 4 2 The major circuits of the power supply are shown on power transformer The adjusted ac is then stepped down b the overall block diagram of Figure 4 1 The three phase ac the power transformer and receives full wave rectification input passes through normally closed contacts of contactor and filtering before appearing at the output bus bars as a K2 to the SCR regulator circuit Under normal operating constant de output voltage or current conditions K2 is maintained energized by the overload cir cuit as will be explained later The regulator contains three 4 3 Feedback Loop SCR s one per phase which operate in conjunction with the firing circuits error amplifier and Constant Voltage 4 4 During normal operation the feedback signals 41 2fined ad ta be an RL ion ali ase ifer cur zuit the ac aal are 3 his bit controlling the SCR firings
20. VE NOTE LEAD LENGTHS FROM ANO BUSES ON EACH UNIT TO LOAD R_ SHOULD BE EQUAL Figure 3 8 Auto Parallel Operation of the slave will be approximately equal to the master s oL put current regardless of the load conditions Because the output current controls of the slave are operative they should be set 10 maximum to prevent the slave reverting tc constant current operation this would occur if the master output current setting exceeded the slave s 3 47 Remote sensing and programming can be used thour the strapping arrangements shown in Figure 3 8 show local sensing and programming 3 48 Auto Series Operation Figure 3 9 3 49 Two maximum SCR 10 power supplies can be oper ated in Auto Series to obtain a higher voltage than that available from a single supply When this connection is usec the output voltage of the slave supply varies in accordance with that of the master supply At maximum output volt age the voltage of the slave is determined by the setting of the front panel VOLTAGE controls on the master The master supply must be the most positive supply of the series The output CURRENT controls of the slave unit are Operative and the current limit is equa to the lowest con trol setting If any of the output CURRENT controls are set too low automatic crossover to constant current opera tion will occur and the output voltage will drop Remote sensing and programming can be used though the strap
21. VLETT HEW is KARD PAC DC Power Supply SCR 10 Series Model 6472C DC POWER SUPPLY SCR 10 SERIES MODEL 6472C OPERATING AND SERVICE MANUAL FOR SERIALS 1125A 0101 AND ABOVE For Serials Above 1125A 0101 a change page may be included 100 Locust Avenue Berkeley Heights New Jersey 07922 HP Part No 06472 90002 Printed July 1971 Section l i GENERAL INFORMATION 1 1 1 5 1 7 1 9 1 11 1 14 TABLE OF CONTENTS Page Description n aara Specifications Options Accessories eesse lastrument Manual Identification Ordering Additional Manuals INSTALLATION once essseescssssesessnesorscenessnneosecanesensaseesaesescensesenssnesansesnvonesscsanesesevoseavsnsesets 2 1 2 3 2 5 2 7 2 9 2 11 2 13 2 15 2 20 2 22 2 30 2 32 Initial Inspection Mechanical Check Electrical Check Installation Data Location Outline Diagram Rack Mounting input Power Requirements 208 230Vac Conversion 380 400Vac Conversion 50Hz Ac Input Option 005 Repackaging for SHIPMeENt saira teen ee cee teen reas asa OPERATING INSTRUCTIONS siiras ipede sinirinin ai 3 1 3 1 3 3 3 5 3 7 3 9 3 11 3 13 3 15 3 18 3 21 3 23 3 25 3 26 3 34 3 40 3 45 3 48 3 53 3 58 3 62 3 63 Turn On Checkout Procedure Operating Modes Normal Operating Mode Constant Voltage Constant Current No Load Operati
22. al difference sig Hence the current balance circuit allows the unit to opt ate with a line to line input voltage unbalance of up to 4 11 Turn On Control Circuit 4 12 The turn on control circuit is a long time constam network which achieves a slow turn on characteristic Ti feature protects load devices by minimizing turn on ove shoot At turn on the control circuit provides an inhi voltage to the firing circuits via the error amplifier keeping the SCR s off for approximately 20 seconds After 20 sec onds the inhibit voltage is removed and the circuit no long er exercises any control over the operation of the supply 4 13 Overvoltage Protection Feature 4 14 The overvoltage protection circuit prevents the output voltage of the supply from exceeding 110 of rating It monitors the output voltage of the supply and if it exceeds the 110 threshold sends a hold signal to the firing cir cuits This circuit is seldom activated because the constant voltage comparator prevents the output voltage from ex ceeding the limit established by the front panel VOLTAGE controls However if the constant voltage comparator should fail the overvoltage protection circuit provides the necessary backup protection 4 15 Overcurrent Protection Circuit 4 16 The overcurrent protection circuit provides backup protection for the constant current comparator being simi lar to the overvoltage protection circuit in this respect The overcurrent
23. ance are accompanied by 42 OPEN CIRCUIT CONSTANT VOLTAGE LOAD OPERATING REGION o c 1 RL gt Re y R Re v CONSTANT CURREN OPERATING REGION Eour SHORT CIRCUIT LOAL o ls Eg FRONT PANEL VOLTAGE CONTROL SETTING Ig FRONT PANEL CURRENT CONTROL SETTING Ro ES CRITICAL OR CROSSOVER VALUE C IS OF LOAD RESISTOR AAA AAA AAA Figure 4 2 Operating Locus of a CV CC Power Supp a drop in the supply output voltage with no accompany change in the output current value With a short circuit across the output load terminais IOUT Es and Egut 4 8 The crossover value of load resistance can be de as Rc Es Is Adjustment of the front panel voltage ar current controls permits this crossover resistance RC set to any desired value from Q too If Ri is greater th Rc the supply is in constant voltage operation while if is less than Rc the supply is in constant current operat 49 Current Balance Circuit 4 10 The current balance circuit maintains the rms amy tude of the input current flowing in the phase B and ph C lines equal to input current flowing in the phase A re ence line To accomplish this the circuit compares the rent in the phase B and C lines with that of the referenc phase A If a difference exists the current balance circ issues an error signal to the firing circuits The firing of phase B or phase C SCR is then advanced or delayed in cordance with the polarity of the origin
24. ated if the input line current rises to about 40 of its normal peak value In this case the increased conduction of Q3 breaks down zener diode VR4 forward biasing CR19 and CR22 and permitting Q2 to conduct The negative output voltage is applied to the firing circuits halting SCR conduction until the output current falls to an acceptable level 4 73 Current Balance Circuit 4 74 This circuit controls the firing of the phase B and phase C SCR s so that the input currents on these lines are equa in amplitude to the input current on the phase A reference line 4 75 The current balancing circuit for each of the corrected phases B and C receives its input directly fram the associ ated input wire which is run physically through the air core of input transformer A3T10 and A3T11 respectively Each input wire serves as the primary of its input transformer inducing the ac current flowing along that wire into the sec ondary winding The ac current waveform on each input wire is of a rectangular shape and consists of positive and negative excursions The negative current flows through the SCR associated with the input line while the positive current 47 flows through a companion diode CR1 CR2 or CR3 anc is in fact the return current from another phase The retu current for the reference phase A flows through diode CR2 or CR3 and therefore appears on the phase B or C line as a positive going pulse The return current for phase B a
25. b After turn on delay period see NOTE rotate CURRENT controls fully clockwise and adjust VOLTAGE controls to obtain desired output voltage on voltmeter 3 1 NOTE The supply output is held off for approximately 10 to 20 seconds after turn on by an internal control circuit c To check out constant current circuit first turn ofi supply Then short circuit output bus bars and rotate VOL AGE controls fully clockwise Turn on supply d After turn on delay adjust CURRENT controls E it uto iset er until desired output current is indicated on ammeter e If supply is equipped with an overvoltage crowbar Option 006 front panel will contain CROWBAR ADJUST pot and lamp If Option 006 is not ordered this portion of panel is blank Refer to Appendix A for crowbar oper ating instructions f TEMPERATURE and OVERCURRENT PRO TECT lamps and are described in Paragraph 3 24 Before connecting actual load to supply read the following paragraphs 3 3 OPERATING MODES 3 4 The power supply is designed so that its mode of oper ation can be selected by making strapping connections be tween particular terminals on the terminal strips at the rear of the power supply The terminal designations are plated on the P C board below their respective terminals The follow ing paragraphs describe the procedures for utilizing the vari aus operational capabilities of the power supply A more theoretical description con
26. bled by the following procedures 3 28 Resistance Programming Figure 3 3 In this mode the output voltage will vary at a rate determined by the con stant voltage programming coefficient refer to Specifica tions Table 1 1 The programming coefficient is determined by the programming current This current is factory adjusted to within 1 H greater programming accuracy is required it may be achieved by adjusting A1R9 as discussed in Para graph 5 76 ALS AB ARI ALO AD A AT AG AS Ad 45 3 A3 AZ A AO elglele Figure 3 3 Remote Resistance Programming Constant Voitage 3 29 The output voltage of the supply should be 0 10mV when zero ohms is connected across the programming termi nals If a zero ohm voltage closer to zero than this is required it may be achieved by inserting and adjusting A1R11 as dis cussed in Paragraph 5 75 3 30 To maintain the stability and temperature coefficient of the power supply use programming resistors that have stable low noise and low temperature coefficient less than 30ppm per degree Centigrade characteristics A switch can be used in conjunction with various resistance values in or der to obtain discrete output voltages The switch should have make before break contacts to avoid momentarily opening the programming terminals during the switching interval SOURCE A JUMPER STRAP ON PC BOARD Al MUST BE v Bus REMOVED FOR THIS MODE REFER TO TEXT Figure 3
27. cerning the operational features of this supply is contained in Application Note 90A Power Supply Handbook available at no charge from your local Hewlett Packard sales office Sales office addresses appear at the rear of the manual 35 NORMAL OPERATING MODE 36 The power supply is normally shipped with its rear terminal strapping connections arranged for constant volt age constant current loca sensing local programming single unit mode of operation This strapping pattern is shown in Figure 3 2 The operator selects either a constant voltage or a constant current output using the front panel controls local programming no strapping changes are necessary 3 7 Constant Voltage 3 8 To select a constant voltage output proceed as fol jows a Turn on power supply and adjust VOLTAGE con trols for desired output voltage with output terminals open b Short circuit output terminals and adjust CUR RENT controls for maximum output current allowable current limit as determined by load conditions If a load change causes the current limit to be exceeded the power supply will automatically cross over to canstant current output at the preset current limit and the output voltage will drop proportionately In setting the current limit al lowance must be made for high peak currents which can Cause unwanted crossover Refer to Paragraph 3 63 3 2 AG ASAIZAS AIO A9 AB A AS A5 AG 5 5 A3 A2 Al A0 7 Rogie oleialelelo o
28. circuit monitors the output current IR drop across sampling resistor and generates a hold signal to the SCR firing circuits if the output current attempts to ex ceed approximately 115 of rating 4 17 Early Overcurrent Protection Circuit 4 18 Further overcurrent protection is afforded by the early overcurrent protection circuit This circuit minimizes output current overshoot during initial short circuit condi tions If the output of the supply is shorted both the line current and the output current attempt to rise The early overcurrent protection circuit monitors the line current phases B and C and generates a turn off signal to the SCR firing circuits if the line current exceeds about40 of the nominal peak value The three SCR s are then turned off momentarily until the line current falls below the 40 threshold and the early overcurrent protection circuit is de activated At this time the constant current comparator and remaining components of the feedback loop again assume control of the SCR s keeping the output current constant despite short circuit conditions 4 19 Although the constant current comparator attempts to keep the output current from rising when the output is first shorted it requires approximately 5 cycles of the input ac before a correction can be made This delay is a result of the overall loop response time and is mostly caused by equal izing networks within the error amplifier The early overcur rent c
29. cting SCR effectively short circuits the supply reducing the output to near zero volts Complete de tails concerning the Option 006 crowbar circuit are given in Appendix A 4 30 DETAILED CIRCUIT ANALYSIS See Schematic Figure 7 7 4 31 SCR Regulator and Firing Circuits 4 32 The SCR regulator operating in conjunction with the firing circuits controls the amount of ac power applied to the primary of the power transformer Each of the three in put phases arbitrarily designated A B and C has an SCR and firing circuit associated with it 4 33 Each SCR conducts upon the simultaneous application of a negative voltage to its cathode input ac and a positive voltage to its gate lead The gate signal firing pulse used to turn on the SCR is a positive going pulse of about 3 5 volts having a duration of approximately 50usec Once the SCR is fired it remains in conduction even though the gate input is removed until the input ac swings positive 4 34 inductors L1 L2 and L3 limit surge currents due to the conduction of their respective SCR s A capacitive net work connected across each SCR filters voltage transients caused by contactor K2 when it is energized or deenergized Also connected across each SCR is a diode CR1 CR3 which protects the SCR against reverse voltages and also serves as the return path for the current from one of the other phases 4 35 Firing Circuits The three phase firing circuits receive the output from
30. d A3T3 are connected in an deita deita configuration as follows T1 0V to T2 400V T2 0V to T3 400V and T3 0V to T1 400V The 380V taps on the three transformers are left open 2 30 50Hz Ac Input Option 005 2 31 For operation from a 50Hz source it is necessary only to readjust the output ripple as described in Paragraph 5 94 in rare instances it may be necessary to readjust the transi ent recovery potentiometer A1R48 if the supply shows signs of oscillating 2 3 2 32 REPACKAGING FOR SHIPMENT 2 33 To insure safe shipment of the instrument it is reco mended that the package designed for the instrument be used The original packaging material is reusable If it is nc available contact your focal Hewlett Packard field office 1 obtain the materials This office will also furnish the addre of the nearest service center to which the instrument can t shipped Be sure to attach a tag to the instrument specifyi the owner model number full serial number and service 1 quired or a brief description of the trouble SECTION MI OPERATING INSTRUCTIONS aun ae a TER MAMIE sort lt lt A E Figure 3 1 Front Panel Controls and Indicators Typical SCR 10 Supply 3 1 TURN ON CHECKOUT PROCEDURE 3 2 The following checkout procedure describes the use of the front panel controls and indicators Figure 3 1 and ensures that the supply is operational a Set LINE ON switch O to on and observe that pilot lamp 2 lights
31. d region without being damaged it cannot be guaranteed to meet all of its performance specifications 3 23 Protection Circuits 3 24 This supply contains an internal overload protection circuit which shuts off the supply in the event of a pro longed overcurrent or overtemperature condition details given in Section IV This circuit also illuminates the appli cable indicator lamp OVERCURRENT PROTECT or TEMPERATURE on the front panel If one of these lamps should light the operator should set the LINE switch to off and turn the VOLTAGE and CURRENT con trois to zero CCW Next the unit should be turned back on If the overload lamp lights again turn the unit off and proceed to Section V Troubleshooting If the lamp does not light the overload may have been caused by a line transient or an improper connection at the rear barrier strip Ensure that all screws on the rear barrier strip are tight and that the strapping pattern agrees with the desired operation 3 25 OPTIONAL OPERATING MODES 3 26 Remote Programming Constant Voltage 3 27 The constant voltage output of the power supply can be programmed controlled from a remote locatian if required Either a resistance or voltage source can be used as the programming device The wires connecting the pro gramming terminals of the supply to the remote program ming device should be twisted or shielded to reduce noise pickup The VOLTAGE controls on the front panel are automatically disa
32. e feedback loop seriously enough to cause oscillation If this is the case it is recommended that the following actions be taken a Adjust equalization control A1R48 to remove os cillation or to achieve best possible transient response tor given long toad lead configuration Refer to Paragraph 5 88 for discussion of transien response measurement b If performing adjustment in step a above does not remove oscillation connect a capacitor having similar char acteristics to those of the output capacitors C1 C2 etc used in the supply directly across load using short leads Readjust equalization control R48 as in step a above after making this change 3 44 Although the strapping patterns shown in Figures 3 3 through 3 6 employ local sensing it is possible to Operate a power supply simultaneously in the remote sensing and re mote programming modes 3 45 Auto Parallel Operation Figure 3 8 3 46 Two maximum SCR 10 power supplies can be con nected in an Auto Paralle arrangement to obtain an output current greater than that available from one supply Auto Parallel operation permits equal current sharing under all load conditions and allows complete control of the output current from the master power supply The output current Ald AIZ ARAI AO AS AB AT AG ASAS 49 5 AF A ar Ag ele ollo gielgieiaelgie cle MASTER ojele Tals oe olele AG ABAZAN AIDAS AB AT AS AS AA t 45 5 gt A3 AD AT AO SLA
33. eration permits one knob control of the tota output voltage from a master supply d Auto Parallel Operation The power supply may be operated in parallel with another unit when greater output 1 1 Figure 1 1 Typical 10kW Power Supply SCR 10 Series current capability is required Auto Paralie operation per mits one knob control of the total output current from a master supply e Battery Charging or Discharging The supply can be used in automatic battery charging or discharging applica tions The automatic crossover between constant voltage and constant current permits the operation to be unattend ed 15 SPECIFICATIONS 1 6 Detailed specifications for the power supply are given in Table 1 1 on Page 1 3 ON al n am he an The je 1 7 OPTIONS 1 8 Options are customer requested factory modifications of a standard instrument The following options are availa ble for the instrument covered by this manual Where neces sary detailed coverage of the options is included throughout the manual Notice that the customer must specify one of the five input power options available for this supply when ordering a unit These options 001 002 003 031 and 032 together with the other available options are described below Option No Description 001 208Vac 10 3 phase input 57 63Hz 002 230Vac 10 3 phase input 57 63Hz 003 460Vac 10 3 phase input 57 63Hz 005 50Hz ac
34. even with the power cable removed To avoid injuries always disconnect power discharge circuits and remove external voltage sources before touching components DO NOT SERVICE OR ADJUST ALONE Do not attempt internal service or adjustment unless another person capable of rendering first aid and resuscitation is present DO NOT EXCEED INPUT RATINGS This instrument may be equipped with a line filter to reduce electromagnetic interference and must be connected to a pro perly grounded receptacle to minimize electric shock hazard Operation at line voltages or frequencies in excess of those stated on the data plate may cause leakage currents in excess of 5 0 mA peak SAFETY SYMBOLS Instruction manua symbol the product A will be marked with this symbol when it is necessary for the user to refer to the instruction manual refer to Table of Contents Indicates hazardous voltages H or Indicate earth ground terminal D M The WARNING sign denotes a hazard It calis attention to a procedure practice or the like which if not correctly per formed or adhered to could result in personal injury Do not proceed beyond a WARNING sign until the indicated conditions are fully understood and met WARNING The CAUTION sign denotes a hazard It calis attention to an operating pro cedure or the like which if not correct ty performed or adhered to could result in damage to or destruction of part or all of the prod
35. everse is true during constant current operation 4 59 Under overcurrent conditions U3 can also be driven by the overcurrent protection circuit via OR gate diode CR25 As previously mentioned protection circuit inputs are applied directly to pin 3 of U3 4 60 Feedback networks C15 R50 and C20 R46 shape the high frequency rolloff in the loop gain response to sta bilize the feedback loop 4 61 Overcurrent Protection Circuit 4 62 Stage U2 monitors the output current IR drop acros the sampling resistors and conducts if the output current exceeds about 115 of the output current rating Resistor A1R38 is factory selected to set the 115 threshold point 4 63 Turn On Control 4 64 This circuit minimizes turn on overshoot by keeping the SCR s off for approximately 20 seconds after the unit is turned on At turn on Q4 conducts providing a less posi tive voltage to the error amplifier This voltage keeps the SCR s off until C23 charges up turning off Q4 Diode CR27 provides a quick discharge path for C23 when the supply is turned off 4 65 Overvoltage Protection Circuit 4 66 This circuit prevents the output voltage from exceed ing approximately 110 of the maximum voltage rating Under non overvoltage conditions transistor Q10 is cutoff due to the 12 4V bias connected to its base If the voltage at the output bus becomes positive enough exceeds the 110 threshold Q10 conducts clamping the error amplifier input Resistor R82
36. in 1 is con nected to the output voltage sensing terminal of the supply S through impedance equalizing resistor A1R1 The other input of the differential amplifier pin 10 is connected to a summing point terminal A2 at the junction of the pro gramming resistors and resistor R6 Instantaneous changes in the output voltage or changes in the voltage at the sum ming point due to manipulation of the VOLTAGE controls produce a difference voltage between the two inputs of the differential amplifier This difference voltage is amplified and appears at the output of the differential amplifier pin 11 as an error voltage 4 49 Resistor R2 in series with the summing point input to the differential amplifier limits the current through the programming resistors during rapid voltage turn down Diodes CR1 and CR2 prevent excessive voltage excursions from over driving the differential amplifier w 3 4 50 During constant voltage operation the programming current flowing through the programming resistors VOLT AGE controls is held constant by the action of constant current source Q1 A constant current flowing through the programming resistors assures linear constant voltage pro gramming 4 51 Comparator Protection Circuit used only on Models 6472C 6475C 6477C 6479C and 6483C 4 52 As indicated in the above paragraph heading this cir cuit is only used in the higher voltage Models of the SCR 10 Series of power supplies The circ
37. input Standard instrument is wired for nominal 60Hz ac input Option 005 includes re alignment and in some cases internal rewiring 006 internal overvoltage protection crowbar Not applicable to 6464C Protects delicate loads against power supply failure or operator error Monitors the output voltage and places a virtual short circuit conducting SCR across load with in 10us after preset trip voltage is exceeded For complete specifications refer to Appendix A 023 Rack kit for mounting one supply in standard 19 rack 031 380Vac 10 3 phase input 57 63Hz 032 400Vac 10 3 phase input 57 63Hz 1 2 1 9 Accessories 1 10 One accessory HP Part No 14545A is available w this supply It consists of four snap on casters and can be ordered with the power supply or separately from your loca Hewlett Packard sales office 1 11 INSTRUMENT MANUAL IDENTIFICATI 1 12 This power supply is identified by a three part seri number tag The first part is the power supply model nur ber The second part is the serial number prefix which cx sists of a number letter combination that denotes the dat of a significant design change The number designates t year and the letter A through M designates the month J uary through December respectively with 1 omitted third part is the power supply serial number a different quentia number is assigned to each power supply 1 13 If the serial number on your instrument does not
38. ircuit overcomes this delay by bypassing the error am plifier and injecting its turn off signal directly into the firing circuits With this arrangement correction can begin after only one cycte of the input ac 4 3 4 20 Phase Protection Circuit 4 21 Another protection circuit used in this supply is the phase protection circuit This circuit insures that no damage will occur internally should one or more of the input phases fail or if the ac voltage on all three input lines falls below 25 of the input rating If such a failure does occur the phase protection circuit clamps the feedback control signal off at the input to the error amplifier When the input lines return to normal the operation reverses itself 4 22 Overload Circuit 4 23 This circuit detects the presence of an extended over current or an overtemperature condition and deenergizes contactor K2 if either of these conditions occur With K2 deenergized the 3 phase ac input path is interrupted shut ting down the supply Contactor K2 is also deenergized if the overload circuit receives a trip input from the over voltage crowbar optional circuit 4 24 The overload circuit continuously monitors the line current on phases B and C and deenergizes K2 if the line current exceeds approximately 40 of the nominal rms line rating of the unit for a period of about one second The overload circuit also illuminates the OVERCURRENT PRO TECT lamp on the front panel under these
39. ith the CROWBAR lamp 4 83 After an overload occurs and the condition has been corrected the operator must set the LINE switch to OFF wait at least 3 seconds and then set the LINE switch to ON 4 84 Overtemperature Circuit The overtemperature com ponents are TC1 and paralle connected TEMPERATURE lamp DS3 Thermal switch TC1 is closed without an over temperature condition The near short circuit created by TC1 across TEMPERATURE lamp DS3 keeps the lamp off during this condition If the heat sink temperature rises above the limits specified in Paragraph 4 25 TC1 opens 48 deenergizing contactor K2 and allowing the TEMPERA TURE lamp to light When the unit cools sufficiently T again closes 4 85 Reference Supply 4 86 The reference supply is a self contained feedback ply employing a series regulator The supply provides st reference voltages which are used throughout the unit 4 87 The reference voltages are ail derived froma full v rectifier CR28 through CR33 and filter C25 which p vide an unregulated 24Vdc The regulating circuit consi of series regulator Q5 driver Q6 and differential amplit stage Q7 and Q8 The differential amplifier compares th voitage at the junction of a voltage divider equal resistc R64 and R69 connected across the output 24 8V wit the voltage at the supply s common point Any di ence in voltage is detected and fed to series regulator QE the correct phase and amplitude to maintain the outpu
40. ll conduct during the associated input cycle Moreover at very low outputs the active SCR may skip one or more cycles between conduction periods Because of these factors the regulation stability overshoot and linear programming characteristics of the supply are somewhat degraded at low outputs The minimum outputs in both Constant Voltage and Constant Current operation at which the supply will perform within specifications are given in the output ratings of Table 1 1 in this manual 4 45 Constant Voltage Comparator 4 46 This circuit consists of the front panel programming resistors R1 and R2 a differential amplifier stage A1U1 and associated components and a constant current source A1Q1 An integrated circuit is used for the differential am plifier to minimize differential voltages due to mismatched transistors and thermal differentials 4 47 The constant voltage comparator continuously com pares the voltage drop across the VOLTAGE controls with the output voltage and if a difference exists produces an error voltage whose amplitude is proportional to this differ ence The error signal ultimately alters the conduction angle of the SCR regulators which in turn alter the output cur rent so that the output voltage becomes equal to the voltage drop across the VOLTAGE controls Hence through feed back action the difference between the two inputs to U1 is held at zero volts 4 48 One input of the differential amplifier p
41. mote sensing is accomp lished by utilizing the strapping pattern shown in Figure 3 7 The power supply should be turned off before chang ing strapping patterns The leads from the sensing S ter minals to the load will carry much less current than the load leads and it is not required that these leads be as heavy as the load leads However they must be twisted or shielded to minimize noise pickup 3 42 For reasonable load lead lengths remote sensing greatly improves the performance of the supply However if the load is located a considerable distance from the sup ply added precautions must be observed to obtain satisfac tory operation Notice that the voltage drop in the load leads subtracts directly from the available output voltage and also reduces the amplitude of the feedback error sig nals that are developed within the unit Because of these factors it is recommended that the drop in the negative load lead not exceed 3 volts If a larger drop must be toler ated please consult an HP Sales Engineer NOTE Due to the voltage drop in the load leads it may be necessary to readjust the current limit in the remote sensing mode 3 43 Observance of the precautions in Paragraph 3 42 will result in a low de output impedance at the load However Figure 3 7 Remote Sensing yh another factor that must be considered is the inductance of long load leads This causes a high ac impedance and could affect the stability of th
42. mounted in a standard 19 rack panel NOTES 1 Specifications apply only when a supply is delivering more than 5 of maximum rated output voltage CV opera tion or 5 of maximum rated output current CC operation and b load is drawing more than 100W Restriction b is lifted when supply is delivering more than 30 of maximum rated output voltage CV operation or 30 of maximum rated output current CC operation 2 For operation with a 50Hz input possible only with Option 05 output current is linearly derated from 100 at 40 C to 80 at 50 C Other specifications indicated in Table must be increased by 50 for a 50Hz input 1 3 SECTION II INSTALLATION 2 1 INITIAL INSPECTION 2 2 Before shipment this instrument was inspected and found to be free of mechanical and electrical defects As soon as the instrument is unpacked inspect for any damage that may have occurred in transit Save all packing materials until the inspection is completed If damage is found file a claim with the carrier immediately Hewlett Packard Sales and Service office should be notified 2 3 Mechanical Check 2 4 This check shouid confirm that there are no broken knobs or connectors that the cabinet and panel surfaces are free of dents and scratches and that the meters are not scratched or cracked 2 5 Electrical Check 2 6 The instrument should be checked against its electri cal specifications Section V includes an
43. mounted on standoffs is factory se lected to obtain the desired trip point 4 67 Phase Protection Circuit 4 68 This circuit protects the SCR s and power transformer in case one of the input phases shouid fail The three phase input ac is rectified by CR38 CR39 and CR4Q filtered by C30 and the resultant voltage on the base of Q9 is normal ly negative enough to hold the transistor off However if one of the input phases fails or if all three phases drop be low 25 of the nominal voltage the voltage across C30 be comes positive enough to break down zener diode VR10 and drive Q9 into conduction The conduction of 09 clamps the input to the error amplifier to a less positive voltage thus turning off the SCR s 4 69 Resistor R77 in the base circuit of Q9 is factory se lected to obtain the desired trip point 4 70 Early Overcurrent Protection 4 71 This circuit provides rapid protection for the load during initial short circuit conditions When activated this circuit injects a negative cutoff voltage directly into the fir ing circuits by passing the loop delay caused by the error amplifier 4 72 A voltage that is proportional to the line current is applied to stage A103 from a rectifier and filter shared by the overtoad circuit Without an overload transistor Q3 is conducting but not sufficiently to breakdown VR4 in its coliector circuit Thus A1Q2 is cutoff and the circuit is de activated The circuit becomes activ
44. nected to an elec trical ground The instrument must be connected to the ac power supply mains through a three conductor power cable with the third wire firmly connected to an electrical ground safety ground at the power outlet For instruments designed to be hard wired to the ac power lines supply mains connect the protective earth terminal to a protective conductor before any other connection is made Any interruption of the protec tive grounding conductor or disconnection of the protective earth terminal will cause a potential shock hazard that could result in personal injury If the instrument is to be energized via an external autotransformer for voltage reduction be certain that the autotransformer common terminal is connected to the neutra earthed pole of the ac power lines supply mains INPUT POWER MUST BE SWITCH CONNECTED For instruments without a built in line switch the input power lines must contain a switch or another adequate means for disconnecting the instrument from the ac power lines supply mains DO NOT OPERATE IN AN EXPLOSIVE ATMOSPHERE Do not operate the instrument in the presence of flammable gases or fumes KEEP AWAY FROM LIVE CIRCUITS Operating personnel must not remove instrument covers Component replacement and internal adjustments must be made by qualified service personnel Do not replace com ponents with power cable connected Under certain condi tions dangerous voltages may exist
45. ng block oscillator action Regenerative coupling between the colh and base windings of each transformer T7 T8 and T9 idly drives the transistor into full conduction where it re mains for about 5Qusec until the transformer becomes saturated At this time the collapsing magnetic field retu the blocking oscillator to the nonconducting state 4 37 The firing pulses are taken from the output windin each transformer and applied between the gate and catho of the appropriate SCR Diodes CR2 CR12 and CR22 co nected across the output windings are used to damp out negative overshoot Resistors R1 R11 and R21 provide a bleed path for current flowing out of the SCR gate termi while diodes CR1 CR11 and CR21 block the voltage este lished by the gate current from reaching the output windi 4 38 Capacitors C1 C11 and C21 between base and emi of each blocking oscillator transistor prevent spurious trig ing The base current which flows when the transistors co duct is limited by resistors R3 R13 or R23 connected to each base winding 4 39 Reset Operation At the end of each input line cyc the applicable emitter ramp capacitor C3 C13 or C23 a base capacitor C4 C14 or C24 are reset to their starting voltages 12 4V and 11V respectively The resetting oper ation is performed by the positive going rectified waveform received by the firing circuits at TP32 Figure 4 3 Input diodes CR5 CR15 and CR25 clamp the base of the wave
46. nternal damages that could occur from reverse voltages if one supply is turned on before the other On six models in the SCR 10 Series current limiting resistors are required Values and part numbers for the re sistors and diodes are given in the chart below Model CRS Commercial HP Part No RS Value 6464C A295F 1901 0336 Not required 6466C A90F 1901 0335 Not required 6469C A90A 1901 0338 0 022 6472C 1N3289 1901 0307 0 032 6475C 1N1187A 1901 0320 0 082 6477C 3270 1901 0326 0 202 6479C S3270 1901 0326 0 252 6483C 3270 1901 0326 0 752 3 52 When the center tap of an Auto Series combination is grounded coordinated positive and negative voltages result This technique is commonly referred to as rubber banding and an external reference source may be employed if de sired Any change of the internal or external reference source e g drift ripple will cause an equal percentage change in the outputs of both the master and slave supplies This feature can be of considerable use in analog computer and other applications where the load requires a positive and a negative power supply and is less susceptible to an output voltage change occurring simultaneously in both sup plies than to a change in either supply alone 3 7 3 53 Battery Charging 3 54 The automatic crossover between constant voltage and constant current displayed by the SCR 10 Series make it an ideal supply for battery charging applications Using this feature
47. on Output Ranges Models 6466C and 6483C Only Connecting Load Grounding Operation Beyond Rated Output Protection Circuits Optional Operating Modes diia Remote Programming Constant Voltage Remote Pragramming Constant Current Remote Sensing Auto Parallel Operation Auto Series Operation Battery Charging Battery Discharging Special Operating Considerations Pulse Loading jis ssieissrpseossoporssessasoesvanpnabiniontoasadssiauidiasinrpsass nense snatdntsitanasasnsacasdebseda 3 6 TABLE OF CONTENTS Continued Section Page IV PRINCIPLES OF OPERATION AAN EA PINE E EEA a 4 1 4 1 Overall Block Diagram Discussion 4 3 Feedback Loop 4 9 Current Balance Circuit 4 11 Turn On Control Circuit 4 13 Overvoltage Protection Feature 4 15 Overcurrent Protection Circuit 4 17 Early Overcurrent Protection Circuit 4 20 Phase Protection Circuit 4 22 Overload Circuit 4 26 Reference Supply 4 28 Overvoltage Crowbar 4 30 Detailed Circuit Analysis doo 4 31 SCR Regulator and Firing Circuits 4 45 Constant Voltage Comparator 4 51 Comparator Protection Circuit 4 53 Constant Current Comparator 4 57 Error Amplifier A ct 4 61 Overcurrent Protection Circuit 4 63 Turn On Control voce 4 65 Overvoltage Protection Circuit r 4 67 Phase Protection Circuit 4 70 Early Overcurrent Protection 4 73 Current Balance Circuit 4 78 Overload Circuit 4 85 Reference Supply
48. originate within the constant voltage or constant current comparator The SCR s are also controlled by the current balance circuit and in certain in stances by various protection circuits as will be explained subsequently During constant voltage operation the con stant voltage comparator continuously compares the output voltage of the supply with the drop across the VOLTAGE controls Hf these voltages are not equal the comparator pro duces an amplified error signal which is further amplified by the error amplifier and fed back to the firing circuits On the basis of the amplitude and polarity of the feedback signal the firing circuits then issue a phase adjusted firing pulse to each SCR so that the original difference is counteracted In this manner the constant voltage comparator helps to main tain a constant output voltage and also generates the error signals necessary to set the output voltage at the level estab lished by the VOLTAGE controls 4 5 During constant current operation the constant cur rent comparator detects any difference between the voltage drop developed by the load current flowing through the cur rent sampling resistor and the voltage across the CURRENT controls if the two inputs to the comparator are momentar ily unequal an error signal is generated which after ampli fication alters the firing angle of the SCR s by the amount necessary to reduce the error voltage at the comparator in put to zero Hence
49. ping arrangements shown in Figure 3 9 show loca sensing and programming CAUTION Model 6483C of the SCR 10 Series cannot be operated in Auto Series because this supply can not be floated at more than 100 Vdc off ground However Auto Tracking can be utilized to obtain coordinated positive and negative volt ages if the center tap of the combination is grounded refer to Paragraph 3 52 3 50 In order to maintain the temperature coefficient and stability specifications of the power supply the external re sistors Rx shown in Figure 3 9 should be stable low noise low temperature coefficient less than 30ppm per de gree Centigrade resistors The value of each resistor is de pendent on the maximum voltage rating of the master supply The value of Rx is this voltage divided by the Con stant Voltage programming current of the slave supply 1 Kp where Kp is the resistance programming coefficient The voltage contribution of the slave is determined by its voltage contro setting 3 51 Protection diodes CRs connected across the output BIG AS AZ A AJO AG AB AY A6 AB AA ps poes MASTER Ry i o old toleo AI4 AIS AI All AiO A9 AS A7 AG AS AG 5 S j AB A2 Ai AO SLAVE 1 TE Bus aus Rs CRs NOTE A JUMPER STRAP ON PC BOARD Al MUST BE REMOVED FOR AUTO SERIES OPERATION REFER TO TEXT Figure 3 9 Auto Series Operation of each supply prevent i
50. ply will automatically cross over from constant voltage to constant current opera tion and vice versa if the output current or voltage exceeds these preset limits 1 3 Many protection circuits are included in the supply to protect the regulator SCR s against excessive current or voltage and to protect the user s load The supply also con tains the front panel trouble lamps associated with some of the protection circuits 1 4 Output voltage and current are continuously monitor ed on two front panei meters Input power is connected to a four pin connector on the rear of the unit The output terminals are heavy busbars also mounted at the rear of the unit Terminal strips at the rear of the unit allow ease in ex panding the operational capabilities of the instrument A brief description of these capabilities is given below a Remote Programming The power supply output voltage or current may be programmed controlled from a remote location by means of an external voltage source or resistance b Remote Sensing The degradation in regulation which occurs at the load due to voltage drop in the load leads can be reduced by using the power supply in the re mote sensing mode of operation c Auto Series Operation Two power supplies may be used in series when a higher output voltage is required in the constant voltage mode of operation or when greater voltage compliance is required in the constant current mode of operation Auto Series op
51. ppears on the input lines of phase A or C and the retur current for phase C appears on the input line of phase A or phase B 4 76 itis the function of each current balancing circuit to maintain the amplitudes of these positive and negative in put currents equal The positive pulses are rectified by CR46 CRA8 filtered by C34 C44 and the resultant posi tive de current is applied to the pin 2 of U4 U5 via sum ming resistor R95 R 115 The negative excursions are recti fied by CR45 CR47 filtered by C35 C45 and the negative de current is summed with the positive current by summin network R94 R95 R114 R115 If the amplitude of the positive and negative currents are unequal an error signal is developed at the output of U4 U5 and fed to the firing circuits This error signal affects the bias on the base of Q2 Q3 and ultimately advances or delays the firing of the SCR s according to the polarity of the original error signal Once the amplitudes of each of the positive and negative input currents become equal no error signal zero volts is generated by U4 U5 4 77 Potentiometers R101 and R121 provide a means of offsetting minor differences in the phase B and phase C current balance loop 4 78 Overload Circuit 4 79 The overload circuit detects the presence of an over temperature or extended overcurrent condition and deener gizes power contactor K2 if either of these conditions oc cur The circuit also provides a visual indication of both
52. rip as illustrated in Figure 3 11 Also a jumper strap on P C Board A1 must be removed see Figure 7 1 for loca tion Removal of this jumper ensures that the internal pro gramming current does not flow into terminal A2 Before operation the user should make sure that the interconnect ing leads between supply and battery are secure and cannot become opened 3 60 The supply initially operates in constant current mode at the value set by the current control When the battery voltage is high the supply output voltage will be low and as the battery discharges the supply output voltage increases A constant voltage is maintained across Rx constant cur rent through Rx This condition will prevail until the bat tery voltage drops to zero At this point the supply will switch aff and no more current will flow through Rx Diade CRp protects the supply against reverse voltages As shown on Figure 3 11 Rx must be selected so that its IR drop is less than the maximum rated output of the supply yet greater than the battery voltage 38 AS A4 45 S ABAZALAD olo 212 21e lalola Ry Ey la BUT Ryta 10K MUST BE lt RATED OUTPUT VOLTAGE OF SUPPLY ANO gt Ep NOTE A JUMPER STRAP ON PC BOARD Al MUST BE REMOVEO FOR BATTERY DISCHARING REFER TO TEXT Figure 3 11 Battery Discharging 3 61 The procedure for the connection of the componen in this configuration is as follows a Turn off the power supply and rota
53. rrent Less than 0 06 plus 85mA change in output per degree Centigrade change in ambi ent following 30 minutes warm up STABILITY Constant Voltage Less than 0 15 plus 16mV total drift for 8 hours following 30 minutes warm up under constant ambient conditions Constant Current Less than 0 3 plus 0 35A total drift for 8 hours following 30 minutes warm up under constant ambient conditions TRANSIENT RECOVERY TIME Less than 50ms 100ms is required for output voitage recovery in constant voltage operation to within 2V 0 75V of the nominal output voltage following a load change from full load to half load or vice versa NOTE 2 METERS A front panel voltmeter 0 80V and ammeter O 180A are provided Accuracy is 2 of full scale RESOLUTION Constant Voltage 64mV is the minimum output voltage change that can be obtained with the front panel controls Constant Current 0 15A is the minimum output current change that can be obtained using the front panel controls REMOTE RESISTANCE PROGRAMMING Constant Voltage 300 ohms volt Accuracy 2 All programming terminals are on a rear barrier strip Constant Current 6 7 ohms ampere Accuracy 2 All programming terminals are on a rear barrier strip COOLING Forced air cooling is employed by means of an inter nal fan WEIGHT 500 ibs net 555 lbs shipping SIZE 16 3 4 W x 26 1 4 H x 26 1 8 D The unit can be
54. sistance and the resistor across the programming terminals 3 38 Voltage Programming With Gain Figure 3 6 The power supply output current can be programmed using an external voltage source with variabie gain by utilizing the strapping pattern shown in Figure 3 6 tn this mode the output current will vary linearly from 0 te maximum rating when the voltage source is programmed from 0 to 6 2 volts The value of the voltage source appearing across terminals A9 and A10 shouid not exceed 7 4Vdc if possible damage to the instrument is to be avoided 3 39 External resistor Rp should have stable low noise and low temperature coefficient less than 30ppm per de gree Centigrade characteristics in order to maintain the stability and temperature specifications of the power supply AK ABAIZAH AIO A9 AB A7 AG AS M 5 S A3 A AL AD jo ejojolejelolo e iglgle oldie VOLTAGE i SOURCE 2 NOMINAL 0 6 2 VOC Figure 3 6 Remote Voltage Programming Non Unity Gain Constant Current Note that it is possible to use the front panel current con trols already in the supply R3 and R4 as the gain control Rp by simply removing the externa Rp and strapping ter minais A5 and AS together 3 40 Remote Sensing Figure 3 7 3 41 Remote sensing is used to maintain good regulation at the load and reduce the degradation of regulation which would occur due to the voltage drop in the leads between the power supply and the load Re
55. t stant The 6 3 and 8 2 voltages are developed across 2t diodes VR1 and VR5 Output capacitors C27 and C28 s bilize the regulator feedback loop
56. t the output power distribution terminals be remotely located from the power supply then the power supply output terminals should be connected to the remote distribution terminats via a pair of twisted or shielded wires and each load should be sepa rately connected to the remote distribution terminals For this case remote sensing should be used Refer to Para graph 3 40 3 18 Grounding 3 19 Positive or negative output voltages can be obtained from the supply by grounding either output bus If the output is floated neither output bus grounded it can be operated up to 100Vdc above ground 300Vdc above ground for Models 6475C 6477C and 6479C 3 3 3 20 When grounding the output the customer s ground must be used and connected to the desired output bus on the supply Do not ground the output at the supply s chassis or at the ac ground terminal on the rear of the supply These points are at safety ground and are not the neutral of the power source refer to Section 11 By fol lowing these recommendations and running a separate lead from each output bus to the load the user will be doubly certain that no load current will flow through the ac input wires to the supply 3 21 Operation Beyond Rated Output 3 22 The shaded area on the front panel meter face indi cates the approximate amount of output voltage or curren that may be available in excess of the normal rated output Although the supply can be operated in this shade
57. te the cur rent control full counterciockwise The voltage control will be disconnected by step b b Remove the designated jumpers A2 to A3 and P C Board and connect A2 to the negative terminal of the battery through 10k resistor c Connect the negative terminal of the supply to th positive terminal of the battery d Insert Rx between the positive terminal of the su piy and the negative terminal of the battery energize the supply and rotate the current control to the desired dis charge current as read on the frant panel meter 3 62 SPECIAL OPERATING CONSIDERATION 3 63 Pulse Loading 3 64 The power supply will automatically cross over fron constant voltage to constant current operation or the re verse in response to an increase over the preset limit in the output current or voltage respectively Although the preset limit may be set higher than the average output cur rent or voltage high peak currents or voltages as occur in pulse loading may exceed the preset limit and cause cross over to occur If this crossover limiting is not desired set the preset limit for the peak requirement and not the average SECTION IV PRINCIPLES OF OPERATION OVERCURREKT PROTECTION 24V UNREG IES REFERENCE 8 24 CONSTANT Pd CURRENT COMPARATOR CURRENT Lo PROTECTION CURRENT SAMPLING RESISTOR puestas nee FULL WAVE 3 PHASE PHASE B 41 FORMER RECTIFIER AC INPUT PHA
58. the IR drop across the current sampling resistor and therefore the output current is maintained at a constant value 46 Since the constant voltage comparator tends to achieve zero output impedance and alters the output current when ever the load resistance changes while the constant current comparator causes the output impedance to be infinite and changes the output vo tage in response to any load resistance change it is obvious that the two comparison amplifiers can not operate simultaneously For any given value of load re sistance the power supply must act either as a constant volt age source or as a constant current source it cannot be both 4 7 Figure 4 2 shows the output characteristic of a con stant voltage constant current power supply With no load attached RL Iguy 0 and EgurT Es the front panel voltage control setting When a load resistance is ap plied to the output terminals of the power supply the out put current increases while the output voltage remains con stant point D thus represents a typical constant voltage op erating point Further decreases in load resistance are ac companied by further increases in IOUT with no change in the output voltage until the output current reaches Is a value equal to the front panel current control setting At this point the supply automatically changes its mode of op eration and becomes a constant current source still further decreases in the value of load resist
59. the error amplifier and generate firing pulses that turn on the SCR s in their respective phases at the precise time necessary to fulfill the feedback loop re quirements As indicated on the schematic everything is done in tripticate For each phase there is a blocking oscilla tor which is synchronized so that each SCR conducts at identically the same phase angle in its respective phase 4 36 The input to the firing circuits is the feedback voltage from error amplifier A1U3 This voltage varies between 1V de to 3Vdc with respect to common Y at terminal A7 as a function of the output conditions The feedback voltage is applied to an integrating network R7 C3 R17 C13 and R27 C23 in the emitter circuit of each blocking oscillator The emitter capacitors produce a steadily rising ramp volt age whose origin is approximately 12 4V see Figure 4 3 The waveform on the base of each blocking oscillator is mainly the result of internal generators A2R28 A2C4 44 BASE BLK OSC TP 22 EMITTER SUK Osc TP 25 Figure 4 3 SCR Firing Circuit Timing Diagram A1R100 A2C14 and A1R120 A2C24 which produce ar 11 msec wide rectangular shaped waveform The 5 6msec wide negative portion is flattened by the action of clamp diodes CR6 CR16 and CR26 The positive going ernitrer voltage rises to meet the base voltage and when the base emitter bias reaches about 0 6Vdc the applicable transist Q1 Q2 or Q3 becomes forward biased initiati
60. uct Do not proceed beyond a CAUTION sign until the indicated con ditions are fully understood and met CAUTION DO NOT SUBSTITUTE PARTS OR MODIFY INSTRUMENT Because of the danger of introducing additional hazards do not install substitute parts or perform any unauthorized modification to the instrument Return the instrument to a Hewlett Packard Sales and Service Office for service and repair to ensure that safety features are maintained instruments which appear damaged or defective should be made inoperative and secured against unintended operation until they can be repaired by qualified service persannel sisto ERRATA In Figure 3 5 connect programming re below In parts list under Mechanical change the between terminals Al and A6 as shown 1 recten HP P N of the cable clamp to 0100 0437 Programming resistor should not be com to terminal A8 un page 3 4 change title of Figure 3 4 to read Remote Voltage Programming Constant AIAAISAIZATE AIOAG AB AT AE AS A4 455 ABAD AT Voltage Unity Gain Cora Parras CJ hal ti 9 ERRATA Add the following at the end of paragraph 2 17 Fuses F1 F2 and F3 70A each in the phase A B and C lines respectively are lo cated inside the unit behind the rear panel Fuses F4 F5 and F6 300mA each connected in the reference supply power input circuit are located on the rear panel fuses F7 and F8 1 64 each in the phase B and C input lines to the T5
61. uit consists of a small three phase power supply which is used to forward bias diode A1CR3 The power supply consists of wye connected trans formers A3T1 A3T2 and A3T3 and a half wave rectifier A1CR5 CR6 CR7 and filter A1C4 During normal oper ation this supply forward biases protection diode CR3 which is connected in series with the summing input to A1U1 pin 10 Under these conditions the diode acts as a near short circuit and has no effect on the operation of the constant voltage comparator However under no load con ditions or with a highly capacitive load if the supply is rapidly down programmed diode CR3 becomes reverse biased due to a positive going transient at its cathode With diode CR3 reverse biased the input path to comparator A1U1 is opened preventing damage to the device 4 53 Constant Current Comparator 4 54 This circuit is similar in appearance and operation 10 the constant voltage comparator circuit It consists of the coarse and fine current controls R3 and R4 and a differ ential amplifier stage U2 and associated components As in the constant voltage comparator an integrated circuit is used for the differential amplifier to minimize differential voltages due to mismatched transistors and thermal differ entials 4 55 The constant current comparator circuit continuously compares the voltage drop across the CURRENT controls with the voltage drop across the current sampling resistors A4R123A A4R123
62. veshape is flattened considerably Another cause of distor tion is high line impedance The user should contact the fac tory if trouble is experienced in this area 2 20 208 230Vac Conversion 2 21 To convert the unit from a 208Vac Option 001 to a 230Vac Option 002 input or vice versa it is necessary on ly to restrap transformers T4 T5 and A3T1 T2 and T3 No other changes are necessary because the components used for Options 001 and 002 are identical The schematic diagram Figure 7 7 shows the transformers noted above 2 2 strapped for 230Vac operation Hence to convert the u from a 208Vac input to a 230Vac input remove the 201 ac jumpers and connect the transformers as shown on tk schematic To convert the unit from a 230Vac input to i 208Vac input simply use the 208V terminals as follows a With the unit off remove jumper between T5 2 and T5 6 Connect new jumper between T5 2 and T5 5 Disconnect wire from fuse F8 to T5 6 and connect it be tween F8 and T5 5 b For transformer T4 remove three straps betwee A1 230 B1 230 and C1 230 and connect a strap betwi A1 208 B1 208 and C1 208 c On transformers A3T1 A3T2 and A3T3 disco nect three jumpers between T1 OV and T2 230 T2 0V and T3 230 and T3 OV and T1 230 Connect three jur ers as follows T1 OV to T2 208 T2 0V to T3 208 anc T3 0V to T1 208 2 22 380 400Vac Conversion 2 23 To convert the unit from a 380Vac Option 031 t 400Vac Option 032 input or
63. vice versa it is necessary ly to restrap transformers T4 T5 and A3T1 T2 and T3 No other changes are necessary because the components used for Options 031 and 032 are identical 2 24 Transformer Connections for 380Vac Input For a 380Vac input the OV tap on the primary transformer T5 connected to fuse F7 and the 380V tap is connected to fi F3 The 400V tap is open The secondary windings are cc nected as shown on the schematic Figure 7 7 2 25 Transformer T4 is connected in the delta star confi ration shown on Figure 7 7 For 380Vac operation conni tap A1 to tap 380 on the B section tap B1 to tap 380 of the C section and tap C1 to tap 380 of the A section Thi three 400V taps are open 2 26 Transformers A3T1 A3T2 and A3T3 are connectec in the delta delta configuration shown on Figure 7 7 For 380 Vac operation connect T1 OV to T2 380V T2 OV te T3 380 and T3 OV to T1 380V The 400 taps on the thr transformers are open 2 27 Transformer Connections for 400Vac Input For a 400Vac input the OV tap on the primary of T5 must be connected to fuse F7 and the 400V tap must be connecte to fuse F8 The 380V tap is left open Secondary taps re main connected as shown on Figure 7 7 2 28 For transformer T4 delta star configuration tap A is connected to tap 400 on the B section tap B1 is connec ed to tap 400 on the C section and tap C1 to tap 400 on the A section The three 380V taps are left open 2 29 Transformers A3T1 A3T2 an

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