Maximal efficiency of an induction slip-ring motor

This article presents considerations on the condition of the occurrence of maximum efficiency in the three-phase slip-ring induction motor supplied by a constant voltage value. A relationship was derived, which allows to calculate with great accuracy the location of maximum efficiency. Comparison of laboratory results with the results of efficiency calculations confirmed the possibility of analytical determination of the output power for maximum efficiency. A general condition for the occurrence of maximum efficiency was formulated, which speaks about the approximate equality of no-load losses and losses in the windings of the rotor current. Calculation tests performed for two groups losses for maximum efficiency point confirmed the general condition of maximum efficiency. Laboratory studies were conducted using the slip-ring motor with rated power PN = 0,8 kW and rated speed nN = 905 rpm