COMPARATIVE ANALYSIS OF A TRANSFER FIELD MACHINE AND AN INDUCTION MACHINE

This work presents a comparative analysis of a transfer field machine (TFM) and a polyp-phase induction machine (IM) . Although the two machines belong to two different classes of machine and quite different in physical configuration , yet both display similar torque – Slip characteristics. However, the synchronous speed of the transfer field machine is ωo/2, that is, one-half that of the induction machine. In their principle of operation, the induced electromotive force (e.m.f) as well as the frequency of this induced e.m.f in both the auxiliary winding of the transfer field machine and the rotor of an induction machine, is proportional to slip. The self inductance matrix of the two machines are derived and both shown to be independent of the rotor angular position. However, the mutual coupling inductance in both cases are dependent on rotor angular position. For the transfer field machine, in addition to rotor angle dependence, it also depends on the difference between the direct - and quadrature-axes reactances. Consequently, the machine produces reluctance torque as a result of the rotor pole –axis trying to align with the axis of the maximum flux. But that of induction machine is by alignment of fields, that is, the rotating magnetic field of the rotor trying to catch up with that of the stator. Under steady-state performance, the transfer field machine exhibited a lower pull out and starting torque as well as lower efficiency than the induction machine. In dynamic mode, the torque versus speed characteristic of both machines are very identical which is akin to what obtains in the steady – state simulation. Also the starting current of the transfer field machine is not high – a feature that makes it possible for the transfer field machine to tolerate a longer starting time without any major disturbance to the supply unlike the induction machine.