A multiaxle AC induction motor drive with current source inverter

Electric traction vehicles usually employ two or more axles to transmit the drive torque to the wheels. Several ac squirrel cage induction motors driven in parallel from a common inverter produce poor torque sharing and large motor derating even for very small (less than one percent) differences in the diameters of the wheel sets attached to different axles of the vehicle. This paper presents two new converter systems using a common chopper current source and two current source inverters. The two inverters are in series and parallel connections for the converter systems A and B respectively. The two converter systems have been analyzed in this paper. A method of calculating the torque and thrust distribution using the equivalent circuits has been developed. Theoretical results have been obtained to show that the converter system A (series connection) is stable in both motoring and braking regions. On the other hand, the converter system B (parallel connection) has lower losses, is stable in the motoring region and is unstable in the braking region. A method to stabilize the converter system B in the braking region is briefly discussed. Experimental results have been obtained to verify the theoretical predictions.