Inverter switching power switching tube fault diagnosis method
Frequency control system is composed of two parts: frequency converter and motor, but the frequency converter part has a higher probability of failure, and an important factor leading to the high failure rate of the frequency converter is the high incidence of switching tube failure. For the fault diagnosis method of switching tube, there are mainly four methods: expert system method, voltage detection method, intelligent algorithm, and current detection method.
(1) The expert system method refers to the experience of fault diagnosis as the basis of the foundation, combined with the specific situation, the possible faults will be enumerated, and constantly enriched and summarised, and finally formed a systematic knowledge base. Then when the fault occurs again, through the query of this knowledge base can make a diagnosis, but the disadvantage of this diagnostic method is that the knowledge base can not be established thoroughly complete and complete.
(2) Voltage detection method is to diagnose the fault by examining the deviation of the motor phase voltage, line voltage or neutral voltage from normal when the inverter is faulty.
(3) Intelligent algorithm, which refers to the general optimisation algorithm. In the frequency control system, intelligent algorithms mainly include artificial neural networks, wavelet analysis, and fuzzy control.
(4) Current detection method, this method is mainly to control the switching tube by grasping the current value and normalising the current.
After the failure of the switching tube, there are two ways to recover: one is to use redundant control; the other is fault-tolerant control. Redundant control is used in systems with high reliability. It is the application of redundant switching when there is a switching tube failure during operation. Fault tolerant control is where each phase of the bridge arm is connected to the motor through a relay. During normal operation, the relay for the neutral phase of the motor is disconnected and this phase is not activated. When a switching tube in one section fails during operation, the relay for that phase is disconnected, thus enabling losses due to sudden failure to be minimised.
