Leroy Somer AVR R438
For both AREP&PMG excitation systems,the alternator voltage regulator is the R438.With AREP excitation,the R438 electronic AVR is powered by two auxiliary winding which are independent of the voltage match circuit.The first winding has a voltage in proportion to that of the alternator,the second have a voltage in proportion to the stator current.
The power supply voltage is rectified and filtered before being used by the AVR monitoring transistor.This consists of a "PMG"(permanent generator).This is fitted at the rear of the machinge and connected to the R438 AVR.The PMG supplies the AVR with constant voltage which is independent of the main alternator winding.As a result the machine has a short-circuit current capacity and good immunity to distrotions generated by the load.The AVR monitors and corrects the alternator output voltage by adjusting the exitation current.50/60Hz selection via the ST3 jumper.
The LAM system is integrated in the R438 AVR as standard.Role of the "LAM(load adjustment module)"On application of a load,the rotation speed of the generator set decreases.When it passes below the preset frequenecy threshold,the LAM causes the voltage to drop by approximately 13% or 25% and consequently the amount of active load applied is reduced by approximately 25% to 50%,until the speed reaches its rated value again.
Hence the LAM can be used either to reduce the speed variation(frequency) and its duration for a given applied load,or the increase the applied load possible for one speed variation(turbo-charged engine).To lowest requency in steady state.During load impacts,the function help the genset to return to its rated speed faster thanks to a gradual increase in voltage according to the principle:
If the speed drops between 46 and 50Hz,the rated voltage follows a fast gradient as it is restored.
If the speed drops below 46Hz,since the engine need more help,the voltage follows a slow gradient as it returns to the reference value.
Voltage regulation +/-0.5% at steady state and constant speed
Phase to phase voltage sensing
Controls by transistor means the regulation quality is independant of load applied
Integrated "LAM" system to cope with increased loads applied to the engine
Suitable for high levels of viration and harsh environments
The R438 is compatible with other modules giving additional functions
Standard power supply: AREP or PMG
Rated overload current: 8A-10s
Electronic protection(overload,shortcircuit on opening of voltage sensing circuitexcitation overload current for 10 seconds then return to approximately 1A).
Fuse: F1 on X1,X2.8A;slow-250V
Voltage sensing: 5VA isolated via transformer
Voltage regulation +/-1%
Normal or rapid response time via ST2 jumper
Voltage adjustment via potertiometer P2
Current sensing(parallel operation): C.T. 2.5VA cl1,sencondary 1A(optional)
Quadrature drop adjustment via potertiometer P1
Max,excitation current adjustment via P5
Applications to Alternators: LSA 42.2,43.2,44.2
Compatible with the AREP or PMG exitation system