sx440 automatic voltage regulator (avr)
Contents
1. 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 power 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 0 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 Skill requirements of personnel Service and maintenance procedures should only be carried out by experienced qualified engineers technici2. under frequency roll off point UFRO This can easily be changed to 50 or 60 Hz in the field by push on link selection 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 INPUT Voltage 190 264V ac Frequency 50 60 Hz nominal Phase 1 Wire 2 OUTPUT Voltage max 90V dc at 207V ac input Current continuous 4A dc Intermittent 6A for 10 secs Resistance 15 ohms minimum REGULATION 1 see note 1 THERMAL DRIFT 0 04 per deg C change in AVR ambient note 2 TYPICAL SYSTEM RESPONSE AVR response 20ms Filed current to 90 80 ms Machine Volts to 97 300ms 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 BUILD UP VOLTAGE 4 Volts AVR terminals 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 input 0 33A ENVIRONMENTAL Vibration 20 100 Hz 50mm sec 100Hz 2kHz
3. 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 S onwards Generator de rate may apply Check with factory 4 Factory set semi sealed jumper selectable 5 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 TD_SX440 AVR_03 05_03_GB DESIGN DETAIL Voltage Sensing Potential Divider amp Droop O Hand Rectifier Trimmer Low Hz Sensing Detection Loss Detector Reference Voltage Analogue Input 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 Sensing Loss Detector is an electronic changeover switch which normally connects the Amplifier Amp to the Voltage Sensing input and automatically changes over to the Power input when the normal sensing voltage is lost The DC Mixer adds the Analogue input signal th
4. STAMFORD SX440 AUTOMATIC VOLTAGE REGULATOR AVR SPECIFICATION INSTALLATION AND ADJUSTMENTS General description SX440 is a half wave phase controlled thyristor type Automatic Voltage Regulator AVR and forms part of the excitation system for a brush less generator In addition to regulating the generator voltage the AVR circuitry includes under speed and sensing loss protection features Excitation power is derived directly from the generator terminals Positive voltage build up from residual levels is ensured by the use of efficient semiconductors in the power circuitry of the AVR The AVR is linked with the main stator windings and the exciter field windings to provide closed loop control of the output voltage with load regulation of 1 0 In addition to being powered from the main stator the AVR also derives a sample voltage from the output windings for voltage control purposes In response to this sample voltage the AVR controls the power fed to the exciter field and hence the main field to maintain the machine output voltage within the specified limits compensating for load speed temperature and power factor of the generator A frequency measuring circuit continually monitors the generator output and provides output under speed protection of the excitation system by reducing the output voltage proportionally with speed below a pre settable threshold A manual adjustment is provided for factory setting of the
5. T THE GENERATOR DROOP TO 5 AT OPF CLOCKWISE INCREASES THE DROOP VTRIM TO OPTIMISE ANALOGUE INPUT SENSITIVITY CLOCKWISE INCREASES THE GAIN OR SENSITIVITY ADJUSTMENT OF AVR CONTROLS VOLTAGE ADJUSTMENT The generator output voltage is set at the factory but can be altered by careful adjustment of the VOLTS control on the AVR board or by the external hand trimmer if fitted Terminals 1 and 2 on the AVR will be fitted with a shorting link if no hand trimmer is required CAUTION Do not increase the voltage above the rated generator voltage If in doubt refer to the rating plate mounted on the generator case CAUTION Do not ground any of the hand trimmer terminals as these could be above earth potential Failure to observe this could cause equipment damage If a replacement AVR has been fitted or re setting of the VOLTS adjustment is required proceed as follows CAUTION 1 Before running generator turn the VOLTS control fully anti clockwise 2 Turn remote volts trimmer if fitted to midway position 3 Turn STABILITY control to midway position 4 Connect a suitable voltmeter 0 300V ac across line to neutral of the generator 5 Start generator set and run on no load at nominal frequency e g 50 53Hz or 60 63Hz 6 If the red Light Emitting Diode LED is illuminated refer to the Under Frequency Roll Off UFRO adjustment 7 Carefully turn VOLTS control clockwise until rated voltage is reached 8 If instabili
6. ans familiar with the procedures and the equipment Before any intrusive procedures are carried out ensure that the engine is inhibited and the generator is electrically isolated STAMFORD Barnack Road Stamford Lincolnshire PE9 2NB 2006 Cummins Generator Technologies Limited Printed in England Tel 00 44 0 1780 484000 Fax 00 44 0 1780 484100 TD_SX440 AVR_03 06_04_GB
7. e 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 provides the excitation system with the required power to maintain the generator voltage within specified limits Synchronising Circuit Generator Suppression Low Pass Filter Level Power Detector amp Control Generator Driver Devices Exciter Field The Stability Circuit provides adjustable negative ac feedback to ensure good steady state and transient performance of the control system 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 The Synchronising circuit is used to keep the Ramp Generator and Low Hz Detector locked to the generator waveform period The Low Pass Filter prevents distorted waveforms affecting the operation of the AVR control circiut Power Control Devices vary the amount of exciter field current in response to the error signal produced by the Amplifier Suppression components are included to prevent sub cycle voltage spikes damaging the AVR components and also to red
8. ty is present at rated voltage refer to stability adjustment then re adjust voltage if necessary 9 Voltage adjustment is now completed TD_SX440 AVR _03 06_03_GB 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 clockwise 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 using the jumper link 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
9. uce the amount of conducted noise on the generator terminals The Power Supply provides the required voltages for the AVR circuitry TD_SX440 AVR_03 06_03_GB FITTING AND OPERATING O EER K1 K2 P2 P3 P4 XX X 3 Paxx x 3 227 ae Power isolation link normally fitted ONDOOARWN Stability Selection Stability l M1 gt 550kw HL 90 550kW lt 90kW Frequency Selection Indicator LED 50Hz ry oorz UFRO Ose FO Note If replacing an existing SX440 position the links and connections the same as the original SX440 If up grading to an SX440 refer to generator wiring diagram for connection details Note There are two terminals marked 2 Sensing they are connected either one or both can links be used standard positions Warning Electrical shock can cause injury or death Ensure that all personnel operating servicing maintaining or working near this equipment are fully aware of the emergency procedures in case of accidents Before removing the protective covers to carry out service maintenance or repair ensure that the engine is inhibited and the generator is electrically isolated 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 SE
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