Analytical investigation of an induction motor drive under inverter fault mode operations

Improved reliability and fault tolerant operations of converter systems are extremely important for industrial AC drives. An induction motor drive with fault tolerance capability is investigated though an analytical model. After the faulted leg in the six-step voltage source inverter operation has been detected, the motor is driven by the converter reconfiguration known as the four-switch inverter, but with reduced performances. Two possible modes of operation, utilising only four possible voltage vectors, in different ways can be used. For both modes of operation an analytical closed-form solution of the motor currents is derived. Theoretical waveforms are verified by experiments. Experimental results are in good agreement with the theoretical predictions.