Stray Load Loss

Author: E.E. Kimberly

The classification stray load loss includes all losses which vary with the load but which are not accurately determinable. Such losses are caused by:

1. Eddy currents in armature conductors.

2. Short-circuit currents in coils under commutation.

3. Eddy currents in bolts and other solid parts of the armature.

4. Flux pulsations produced by change in the reluctance of the magnetic path at teeth and slots; and flux pulsations produced by currents in coils under commutation.

5. Distortion of the flux in the armature produced by the armature reaction.

Inasmuch as the stray load losses are not accurately determinable, but do actually exist, the recommendation of the American Institute of Electrical Engineers is that they be assumed as 1 per cent of the power output when calculating conventional efficiency of machines having an output of 30 or more hp.