Influence of the sinusoidal supply frequency on the induction motor stray load losses

This papers deals with the influence of the supply frequency on the induction motor stray load losses. Due to the complexity of the stray load losses computation, a fully experimental approach has been chosen. Following the International Standard IEEE 112 method B, the additional losses have been determined in the supply frequency range of 30 Hz up to 80 Hz. As requested by this standard, a sinusoidal supply has been adopted for an 11 kW, 50 Hz, 400 V induction motor. In order to understand if the motor stator phase connection influences the stray load losses, the tests have been performed with both star and delta connections. The test results didn´t show any influence of the motor connection on the stray load losses. About the supply frequency, the obtained results have shown a direct dependence of the stray load losses with the supply frequency. As a consequence, waiting the new International Standards which will define the rules for the induction motor efficiency determination with inverter supply, the results reported in this paper warn that the stray load losses are directly depending on the supply frequency and this cannot be neglected when the motor is used in variable frequency drive, in particular during the flux weakening operation.