PERFORMANCE CHARACTERISTICS OF A TRANSFER FIELD MACHINE OPERATING IN THE ASYNCHRONOUS MODE

ABSTRACT

This thesis presents the performance characteristics of a Transfer Field (TF) machine. In this machine, the two component fields revolving in the airgap are of the same pole number and the speed of operation is inversely proportional to the sum of the two pole numbers, that is, half the synchronous speed 𝜔/2 of a normal induction motor. There is thus, a close relationship between the self-cascaded induction machine and the TF machine. It is shown that if the reactance of the machine is made capacitive by capacitance injection into the auxiliary winding, the current in the machine becomes leading and the machine begins to generate at a sub synchronous speed and motoring at speeds above the synchronous speed resulting in reversed torque-slip characteristics about the slip-axis. With the introduction of variable resistance into the auxiliary winding, the starting torque of the machine is enhanced but the maximum torque in each case is unaltered. However, only the slip at which the maximum torque occurs is altered. This characteristic is consistent with induction motors. It is shown that although the machine operates asynchronously, the torque produced by the machine is synchronous torque. It is also shown that the machine is capable of synchronous operation if at its synchronous speed 𝜔/2 , a dc field is fed to the auxiliary winding of the machine.