Efficiency testing of medium induction motors-a comment on IEEE Std 112-1991

The energy crisis of 1973 focused attention on the efficiency of polyphase induction motors, and the need to have a test procedure that was repeatable and accurate. Medium power induction motors, especially those in the size range 1 through 125 horsepower, were important because of the large number in service and the fact that a significant efficiency improvement through redesign was economically feasible. In response to this the ANSI/IEEE Std. 112, "IEEE Standard Test procedure for Polyphase Induction Motors and Generators" Method B was chosen for testing medium power AC motors for efficiency. The current version IEEE Std. 112-1991 Method B contains several requirements for accuracy improvement which have been found to be effective. Even though the Method B procedure with the additional accuracy requirement has been in use since 1984 no rational has been published to support these extra requirements. The paper discusses the purpose of these improvements, and also points out some weakness in procedure.