The Miniature Two Phase Induction Motor as an Element of an Alternating Current Servosystem

Abstract

After an introduction in which the suitability of this particular machine for servosystem application is explained and its specification of performance outlined,reasons are put forward for the use of its resistance and metric tensors as a mathematical representation of the machine in system simulation. A complete analysis is then formulated for the machine covering true dynamic and steady state operation and extended to include the effects of space harmonics in the machine's magnetomotive force waveform. From this analysis the mathematical model, in the form of the metric and resistance tensors, is derived. New methods of calculating the elements of these tensors are proposed and also a practical method, employing a new locus diagram for the induction motor, for measuring these elements. For the determination of this locus diagram and for eventually corroborating the predicted performance of the machine with it's measured performance, a special dynamometer is designed and made and suitable measuring techniques evolved. As a result of the interpretation of the new locus diagram for a test motor, an improved representation of the rotor of the miniature induction motor is discovered and a new method of determining the effective airgap, which differs from the mechanical dimension due to the effects of machining stresses in the core material, is found. A mathematical model incorporating these improvements and derived from the locus diagram is presented. This model is compared with that obtained from the design data and is then used to predict the full range of performance,both steady state and dynamic, of the test motor. By comparing the measured performance with the predicted performance the efficacy of the model obtained from the locus diagram is established and, thereby, that of the model determined by calculation in the design stages. This comparison serves also to ratify the method of analysis used. The study ends with a brief catalogue of future work consequent upon that of this investigation.