The circuitry of the R438 Automatic Voltage Regulator(AVR) provides closed loop control of the generator output voltage by regulating the exciter field current. The R438 can be powered by AREP or PMG field excitation system and is fitted as an option on:
-1000 Series Generator
-2000 Series Generator
-3000 Series Generator
With the AREP excitation system the R438 AVR is powered by two auxilliary windings which are independent of the voltage detection circuit. With the PMG option the R438 AVR is powered by PMG which is fitted at rhe rear end of the generator.

Specification
Voltage regulation ±0.5%
short circuit capability: 3 × Irated for 10 seconds(AREP or PMG excitation)
Voltage sensing:
95 to 140 volts(50/60Hz) or
170 to 260 volts(50/60Hz)or
340 to 520 volts(50/60Hz)
Response time:
Normal(1 sec) for ±20% voltage variation
or Rapid (0.3 sec) for ±20% voltage variation
Remote voltage adjustment range of: ±0.5%
With the AREP excitation system the R438 AVR is powered by two auxilliary windings which are independent of the voltage detection circuit. With the PMG option the R438 AVR is powered by the PMG which is fitted at the rear end of the generator.