Question: Can you provide your customers with the efficiency of your induction motor models given only an input current value? The answer: Yes

Abstract

This paper describes a simple graphical method for the finding a reasonably-accurate value for the efficiency of any balanced multiphase motor for any arbitrarily-selected value of operating current. The method assumes the following routine conditions: the motor operates at rated voltage and frequency; the stray load loss and the rotor core loss are negligible; the no load speed of the motor is known along with the five Steinmetz Model element values; and that the only model element that varies under normal operating conditions is the reflected rotor resistance, r2/s. The method makes use of a Unit Circle that has been developed from the forward impedance of the traditional six-element-per-phase model illustrated in IEEE Standard 112. This paper elaborates upon a specific facet of the general analyses that have been addressed in previous papers written by the writer; this facet should be of particular interest to motor manufacturing personnel who must provide technical support for their customers.