Diagnostic Method of Switch Tube Fault in Frequency Converter Switching Power Supply
The variable frequency speed control system consists of two parts: the frequency converter and the motor. However, the probability of faults occurring in the frequency converter part is higher, and an important factor leading to the high failure rate of the frequency converter is the frequent occurrence of switch tube faults. There are four main methods for fault diagnosis of switch tubes: expert system method, voltage detection method, intelligent algorithm, and current detection method.
(1) Expert system method refers to the practice of using experience in fault diagnosis as a basis, combined with specific situations, to list possible faults, continuously enrich and summarize them, and ultimately form a systematic knowledge base. So when the fault occurs again, diagnosis can be made by querying this knowledge base, but the drawback of this diagnostic method is that it cannot establish a completely complete and complete knowledge base.
(2) The voltage detection method is used to diagnose faults by examining the deviation of the motor phase voltage, line voltage, or neutral point voltage from normal when a frequency converter malfunctions.
(3) Intelligent algorithms refer to general optimization algorithms. In the variable frequency speed control system, intelligent algorithms mainly include artificial neural networks, wavelet analysis, and fuzzy control.
(4) The current detection method mainly controls the switching transistor by grasping the current value and normalizing the current.
After a fault occurs in the switch tube, there are two methods for recovery: one is to use redundant control; Another type is fault-tolerant control. Redundant control is used in systems with high reliability. When there is a malfunction in the switch tube during operation, redundant switches are used. Fault tolerant control is the connection between each phase bridge arm and the motor through a relay. During normal operation, the relay of the neutral phase of the motor is disconnected and this phase is not activated. When a switch tube in a certain section malfunctions during operation, the relay of that phase will disconnect, thereby minimizing the losses caused by sudden faults.
