An application of deceleration test methods to the determination of induction-motor performance

RETARDATION tests have been used by industry for a long time. They have found their main applications in the determination of certain machine losses, usually friction and windage and core loss. The machines to which these methods have been applied have ordinarily had large mass and low rotational losses with the result that a considerable time would elapse between the time the power was shut off and the time the machine would come to rest. By proper selection of equipment and analysis the same methods may be applied to much smaller machines having relatively short stopping periods. In the present instance the methods have been applied to two double squirrel-cage induction motors, one a 7 1/2-horsepower 6-pole machine, and the other a 5-horsepower 4-pole machine. In each case the inertia was increased to about twice that of the motor alone by the use of a small flywheel. A similar analysis has been applied to acceleration tests on these two motors in which the motors were started at reduced voltage. By combining the acceleration tests with the decleration tests the speed-torque curves of the motors have been obtained. It is hoped that the discussion of the difficulties and the results of these tests will help to indicate the value and limitations of the methods as applied to similar determinations in this and other fields.