Fujitsu Converter Failure & Rework
l, OC1, OC2, OC3
Faulty display as OC1, OC2, OC3, which is one of the most common faults in Fuji converter, it includes over-current in converter accelerating, over-current in the decelerating, and over-current in the constant speed, the main causes of this failure are as below:
(1) Acceleration time length is too short, which is the most common phenomenon in our over-current failure. According to the different load conditions we adjust the acceleration and deceleration time length accordingly, can eliminate this failure.
(2) high-power transistor damage may also cause OC alarm, high-power transistor of Fuji converter has been upgraded for several generations with the development of semiconductor technology, from the early GTR modules such as G2 (P2), G5 (P5), G7 ( P7) series, to the IGBT modules of G9 (P9) series, until the still using IPM module, both from the packaging technology or protection performance, Converter’s features have been greatly improved. High voltage, high current, high frequency, Low power consumption, multi-protection function has become the development trend of a high power transistor module. The damage to the high-power transistor module is mainly due to the following reasons:
a) output load is shorted;
b) load is too large and the large current continues to occur;
c) the load fluctuates greatly, causing the surge current to be too large, which may cause OC alarm and damage the power module.
converter pcb
(3) drive circuit which has been used to drive high-power transistor, if this drive circuit damage will become a cause of over-current alarm. Fuji G7S, G9S are applying PC922, PC923 two various kinds of opto-couplers as the core of the drive circuit, due to the existence of built-in amplifier circuit, the circuit design of PCB board is simple, a number of converter manufacturers including Fuji converter has been widely used. The most common phenomenon of driving circuit damage is the absence of phase, or three-phase output voltage imbalance.
(4) Damage on the detection circuit will lead to the converter display OC alarm, the Hall sensor for detection of current can be affected due to temperature, humidity and other environmental factors, the operating point is prone to drift and resulting in OC alarm.
