... MX321 is a half-wave phase-controlled thyristor type Automatic Voltage Regulator(AVR) and forms part of the excitation system for ... such as Stanford or stanford technical alternator.Technical specificationsInput Voltage 170~220VAC, 3 phase 3A(PMG) Frequency 50 ... speed, over excitation, over-voltage, over-current, LAMRegulation +/- 1.0% Others provided as follows:AVR-SX460AVR-SX440 AVR-MX341 AVR-KRS440