Invester Fault Diagnose Based on Detecting DC Side Current

For diagnosing the inverters transistor base drive open fault in variable frequency drive system, the frequency spectrum in normal, open fault of one transistor and open fault of two transistors in one phase is analyzed by introducing the double Fourier transfor of the switch function: The low frequency spectrum of DC side current contains DC component only when the inverter runs in normal; The low frequency spectrum of DC side current contains the DC component and some harmonic of modulation signal when one transistor is open; The low frequency spectrum of DC side current contains the DC component and the second harmonic of modulation signal only when two transistors in one phase are open. The open fault of one transistor and open fault of two transistors in one phase can be examined by detecting the frequency components of DC side current. Theoretical analysis is verified by esperinent results.