Q: How judging voltage regulator  (AVR) is good or bad? 

A: Determine surge plates (AVR) is good or bad, in the normal coil windings confirm the premise identify F1.F2 excitation power cord with battery power as magnetizing, positive then F1, negative then F2 (waiting) when starting the unit up to the rated speed, the F2 and battery negative phase, the following may occur: 

1: Voltage establish ≥ 400V (determined according to the size of the battery voltage), the detected voltage with a multimeter to check P2.P3.P4AVR there AC190-220V, subject to the normal description of each detection line, and then check the AVR F1, F2 there DC40 -90V voltage output, if any proof surge plates (AVR) in good condition, if there is no or a low DC voltage output, AVR has proved bad. 

2: If no voltage is established or DC voltage ≤ 30V, determined under normal circumstances the windings, which can certainly exciter rectifier diode or surge blanking tube is damaged, should be excluded from AVR failure, should focus on checking the rectifier diodes.