This paper documents a technique for deriving a steady-state, lumped-parameter model for capacitor-run, single-phase induction motors. The objective of this model is to predict motor performance parameters such as torque, loss distribution, and efficiency as a function of applied voltage and motor speed as well as the temperatures of the stator windings and of the rotor. The model includes representations of both the main and auxiliary windings (including arbitrary external impedances) and also the effects of core and rotational losses, The technique can be easily implemented and the resultant model can be used in a wide variety of analyses to investigate motor performance as a function of load, speed, and winding and rotor temperatures. The technique is based upon a coupled-circuit representation of the induction motor. A notable feature of the model is the technique used for representing core loss, In equivalent-circuit representations of transformers and induction motors, core loss is typically represented by a core-loss resistance in shunt with the magnetizing inductance, In order to maintain the coupled-circuit viewpoint adopted in this paper, this technique was modified slightly; core loss is represented by a set of core-loss resistances connected to the ''secondaries'' of a set of windings which perfectly couple to the air-gap flux of the motor, Although this can be shown to be equivalent to the more conventional representation, the form chosen here lends itself to a set of equations which can be simply written using matrix notation, Key to the practicality of this technique is the methodology presented in the paper for deriving model parameters based upon a simple set of measurements. This methodology takes advantage of the speed of digital computation which permits a search of parameter space to find a parameter set that best matches the measured motor performance. Finally, an example of the technique is presented based upon a 3.5 kW, single-phase, capacitor-run motor and the validity of the technique is demonstrated by comparing predicted and measured motor performance.
