Interest is continually being shown in the replacement of variable speed DC machines with an equivalent inverter fed AC machine. This is as true in the field of highly rated machines for traction use. as in the field of smaller industrial drives. In the following work, a general design method is presented that is suitable for the design of induction, and slip ring synchronous machines of the round rotor or salient pole type. The method is based upon machine models that employ surface quantities. This type of model clearly displays the interaction between flux and current, and is readily adaptable for design use. as the amount of detail required is kept to a minimum. Several designs are presented for induction and synchronous machines that satisfy the requirements of a traction motor for use in a high speed locomotive. Performance predictions, based on sinusoidal supply considerations and operating under two commonly used control schemes are shown. The traction motors satisfy the main overall requirement for a minimum size and weight design. In practice the AC traction motors would be supplied by a variable frequency inverter. In view of this, an analysis of the performance of the most suitable induction and synchronous motor designs is presented, when each is being supplied with an inverter of the preferred type. Two inverters are considered, one of the constant voltage type, and one of the constant current type. Computer models are used to predict the machine, voltage current and torque waveforms when both inverters are operated In the 120 degree conduction mode. Experimental results are shown, to verify the computer model of the current source inverter. A 5KVA laboratory squirrel cage induction machine is used for this purpose, in conjunction with a force measuring platform that enables the steady state torque pulsations to be recorded.
|Date of Award||1984|