Stray losses in induction motors

This paper calls attention to the fact that “load losses” on induction motors as described in Section 167 of the present Standardization Rules include some losses which are not actually present when the motor is running under normal operating conditions. An analysis is made of the cause and nature of the so-called load losses and a suggestion is made as to a method of segregating the real load losses from other losses as observed in the power input to the motor at standstill. The conclusion is drawn that motors up to a certain capacity with wire windings have no appreciable load loss. In larger capacities and with conductors of certain types load losses are present. Recommendation is made that Section 167 be revised so as to include a method of determining the load losses of all classes of motors from readings taken at standstill. This will permit the calculation of the true efficiency from no-load and standstill readings.