Low-cost diagnostic method for open-switch faults in inverters

The theory, design, implementation and experimental validation of a novel low-cost online diagnosis and location method for open-switch faults in voltage source inverters is presented. According to the analysis of the operating states in inverters, there are different collector-emitter voltages of the bottom power switches in faulty conditions compared with normal conditions. To reduce cost, the proposed method employs high-speed photocouplers to sense voltages of the bottom switches, and then a sample logic circuit is designed to implement the detection and location of the fault. The developed approach minimises the time interval between the fault occurrence and its diagnosis, and is validated by the experiment.