Stamford Automatic Voltage Regulator
Contents
1. V Hz line as the speed falls below nominal Turning the DIP potentiometer more clockwise increases the V Hz slope providing a greater voltage dip and aiding engine recovery The DIP potentiometer can be set at any desired position to suit a particular engine type OVER EXCITATION EXC TRIP ADJUSTMENT The adjustment is set and sealed in the works and should not be altered An over excitation condition is indicated on the common LED which also indicates under speed running The generator must be stopped to reset an over excitation condition Qa NEWAGE J avk SEG PO Box 17 Barnack Road Stamford Lincolnshire e PE9 2NB 2003 Newage International Limited Reprinted with permission of N I only Printed in England Tel 00 44 0 1780 484000 Fax 00 44 0 1780 484100 Website www newage avkseg com TD_MX341 GB_05 03 022. input 0 33 A OVER EXCITATION PROTECTION 300 ms Set point 75 V de Time delay 10 seconds fixed ENVIRONMENTAL Vibration 20 100 Hz 50mm sec 100Hz 2kHz 3 3g Operating temperature 40 to 70 C Relative Humidity 0 70 C 95 see note 6 Storage temperature 55 to 80 C NOTES 1 With 4 engine governing 2 After 10 minutes 3 Applies to Mod status D onwards Generator de rate may apply Check with factory Factory set semi sealed jumper selectable Any device connected to the analogue input must be fully floating galvanically isolated from ground with an insulation strength of 500V ac 6 Non condensing at TD_MX341 GB_05 03 02 DESIGN DETAIL Stator Voltage Sensing Droop Potential Low Hz Synchronising Divider amp Detection Circuit Hand Rectifier Trimmer Reference Voltage Level Power Anal ip na Ramp Detector amp Control ppu Generator Driver Devices Stability Circuit The main functions of the AVR are Potential Divider and Rectifier takes a proportion of the generator output voltage and attenuates it The potential divider is adjustable by the AVR Volts potentiometer and external hand trimmer when fitted The output from the droop CT is also added to this signal An isolating transformer is included allowing connection to various winding configurations A rectifier converts the a c input signal into d c for further processing The DC Mixer adds the Analogue input signal
3. STAMFORD power MX341 AUTOMATIC VOLTAGE REGULATOR AVR SPECIFICATION INSTALLATION AND ADJUSTMENTS General description MX341 is a two phase sensed Automatic Voltage Regulator and forms part of the excitation system for a brush less generator Excitation power is derived from a three phase permanent magnet generator PMG to isolate the AVR control circuits from the effects of non linear loads and to reduce radio frequency interference on the generator terminals Sustained generator short circuit current is another feature of the PMG system The AVR senses the voltage in the main generator winding and controls the power fed to the exciter stator and hence the main rotor to maintain the generator output voltage within the specified limits compensating for load speed temperature and power factor of the generator Soft start circuitry is included to provide a smooth controlled build up of generator output voltage A frequency measuring circuit continually monitors the shaft speed of the generator and provides under speed protection of the excitation system by reducing the generator output voltage proportionally with speed below a pre settable threshold A further enhancement of this feature is an adjustable volts per Hertz slope to improve engine recovery time on turbo charged engines Soft start circuitry is included to provide a smooth controlled build up of generator output voltage Uncontrolled excitation is limited to a sa
4. er factor Clockwise increases the amount of C T signal injected into the AVR and increases the droop with lagging power factor cos With the control fully anti clockwise there is no droop TRIM ADJUSTMENT An analogue input A1 A2 is provided to connect to the Newage Power Factor Controller or other devices It is designed to accept dc signals up to 5 volts CAUTION Any devices connected to this input must be fully floating and galvanically isolated from ground with an insulation capability of 500 Vac Failure to observe this could result in equipment damage The dc signal applied to this input adds to the AVR sensing circuit A1 is connected to the AVR O volts Positive on A2 increases excitation Negative on A2 decreases excitation The TRIM control allows the user to adjust the sensitivity of the input With TRIM fully anti clockwise the externally applied signal has no effect Clockwise it has maximum effect Normal setting is fully clockwise when used with a Newage Power Factor Controller DIP ADJUSTMENT The DIP adjustment allows some control over the generator voltage dip upon the application of load This feature is mostly used when the generator is coupled to turbo charged engines with limited block load acceptance and operates only when the speed is below the UFRO knee point LED illuminated With the DIP potentiometer fully anticlockwise the generator voltage characteristics will follow the normal
5. fe period by internal shutdown of the AVR output device This condition remains latched until the generator has stopped Provision is made for the connection of a remote voltage trimmer allowing the user fine control of the generator s output An analogue input is provided allowing connection to a Newage Power Factor controller or other external devices with compatible output The AVR has the facility for droop CT connection to allow parallel running with other similarly equipped generators Technical specification SENSING INPUT Voltage 190 264V ac max 1 phase 2 wire Frequency 50 60 Hz nominal POWER INPUT PMG Voltage 140 220V ac max 3 phase 3 wire Current 3A phase Frequency 100 120 Hz nominal OUTPUT Voltage max 120V dc Current continuous 2 7 A Intermittent 6A for 10 secs Resistance 15 ohms minimum REGULATION 1 see note 1 THERMAL DRIFT 0 03 per C change in AVR ambient note 2 SOFT START RAMP TIME 3 seconds TYPICAL SYSTEM RESPONSE AVR Response 10 ms Filed current to 90 80 ms Machine Volts to 97 EXTERNAL VOLTAGE ADJUSTMENT 10 with 1 k ohm 1 watt trimmer see note 3 UNDER FREQUENCY PROTECTION Set point 95 Hz see note 4 Slope 170 down to 30 Hz UNIT POWER DISSIPATION 12 watts maximum ANALOGUE INPUT Maximum input 5V dc see note 5 Sensitivity 1v for 5 Generator Volts adjustable Input resistance 1k ohm QUADRATURE DROOP INPUT 10 ohms burden Max sensitivity 0 07 A for 5 droop OPF Max
6. nt of the VOLTS control on position the AVR board or by the external hand trimmer if fitted 3 Turn STABILITY control to midway position Terminals 1 and 2 on the AVR will be fitted with a shorting 4 Connect a suitable voltmeter 0 300V ac across link if no hand trimmer is required line to neutral of the generator 5 Start generator set and run on no load at nominal CAUTION Do not increase the voltage above the rated frequency e g 50 53Hz or 60 63Hz generator voltage If in doubt refer to the rating plate 6 If the red Light Emitting Diode LED is illuminated mounted on the generator case refer to the Under Frequency Roll Off UFRO CAUTION Do not ground any of the hand trimmer adjustment terminals as these could be above earth potential 7 Carefully turn VOLTS control clockwise until rated Failure to observe this could cause equipment damage voltage is reached 8 If instability is present at rated voltage refer to If a replacement AVR has been fitted or re setting of the stability adjustment then re adjust voltage if VOLTS adjustment is required proceed as follows necessary 9 Voltage adjustment is now completed TD_MX341 GB_05 03_02 FITTING AND OPERATING STABILITY ADJUSTMENT The AVR includes a stability or damping circuit to provide good steady state and transient performance of the generator The correct setting can be found by running the generator at no load and slowly turning the stability control anti cl
7. ockwise until the generator voltage starts to become unstable The optimum or critically damped position is slightly clockwise from this point i e where the machine volts are stable but close to the unstable region OPTIMUM RESPONSE SELECTION The stability selection jumper should be correctly linked A B B C or A C at the bottom of the board for the frame size of the generator see drawing UNDER FREQUENCY ROLL OFF UFRO ADJUSTMENT The AVR incorporates an underspeed protection circuit which gives a volts Hz characteristic when the generator speed falls below a presettable threshold known as the knee point The red Light Emitting Diode LED gives indication that the UFRO circuit is operating The UFRO adjustment is preset and sealed and only requires the selection of 50 60Hz 4 pole 6pole using the jumper link see diagram Adjustment of the UFRO potentiometer will only be necessary if the AVR is being fitted to a 6 pole generator to replace an AVR of an earlier type For optimum setting the LED should illuminate as the frequency falls just below nominal i e 47Hz on a 50Hz system or 57Hz on a 60Hz system DROOP ADJUSTMENT Generators intended for parallel operation are fitted with a quadrature droop C T which provides a power factor dependent signal for the AVR The C T is connected to S1 S2 on the AVR The DROOP adjustment is normally preset in the works to give 5 voltage droop at full load zero pow
8. on condition persists for the specified time period The Power Supply provides the required voltages for the AVR circuitry TD_MX341 GB_05 03_02 FITTING AND OPERATING REFER TO GENERATOR WIRING DIAGRAM LJ ae C FOR CONNECTION DETAILS K1 K2 Power isolation link C normally fitted Droop volts Sensing MX341 links Frequency EXC SARA Selection RIP m p Stability Selection No link 6P50Hz I Indicator I 6P60H Stabilit I gt 550kw F apill LED I 4P50H Y F 0 550kw UFRO 77 4P60H Tl 1 lt 90kw 321 CBA O ol QO SUMMARY OF AVR CONTROLS CONTROL FUNCTION DIRECTION Volts To adjust generator output voltage Clockwise increases output voltage Stability To prevent voltage hunting Clockwise increase the damping effect Ufro To set the ufro knee point Clockwise reduces the knee point frequency Droop To set the generator droop to 5 at Opf Clockwise increases the droop Vtrim To optimise analogue input sensitivity Clockwise increases the gain or sensitivity Exc trip To set the over excitation cut off level Clockwise increase the cut off level Dip To set the frequency related voltage dip Clockwise increases the voltage dip ADJUSTMENT OF AVR CONTROLS CAUTION VOLTAGE ADJUSTMENT 1 Before running generator turn the VOLTS control fully anti clockwise The generator output voltage is set at the factory but can 2 Turn remote volts trimmer if fitted to midway be altered by careful adjustme
9. the Sensing signal The Amplifier Amp compares the sensing voltage to the Reference Voltage and amplifies the difference error to provide a controlling signal for the power devices The Ramp Generator and Level Detector and Driver infinitely control the conduction period of the Power Control Devices and hence provide the excitation system with the required power to maintain the generator voltage within specified limits The Stability Circuit provides adjustable negative ac feedback to ensure good steady state and transient performance of the control system Over Excitation Detector Exciter Field The Low Hz Detector measures the period of each electrical cycle and causes the reference voltage to be reduced approximately linearly with speed below a presettable threshold A Light Emitting Diode gives indication of underspeed running A further enhancement of this feature is the variable DIP adjustment which provides greater voltage roll off to aid the recovery of turbo charge engines taking large impact loads The Synchronising circuit is used to keep the Ramp Generator and Low Hz Detector locked to the Permanent Magnet Generator waveform period Power Control Devices vary the amount of exciter field current in response to the error signal produced by the Amplifier The Over Excitation Detector continuously monitors the exciter field voltage and provides signals to shut down the power device if an over excitati
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