General Description

MX342-2 is a two phase sensed Automatic Voltage Regulator (AVR) and forms part of the excitation system for a brush-less generator.

Wide speed range, linear volts / Hz and current limit input are special features of this AVR.

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.

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 linearly with speed below a pre-settable threshold.

Soft start circuitry is included to provide a smooth controlled build up of generator output voltage.

Uncontrolled ecitation is limited to a safe period by internal shutdown of the AVR output device. This condition remains latched until the generator has stopped.