PLAN No. 1080. TESTING MOTORS
In testing a motor the machine is loaded by making it drive, usually through a belt, an electric generator. The energy which this generator develops is forced into the same circuit as that from which the driving motor takes its power. Hence, the net energy required to conduct the test is greatly minimized, being in fact equivalent only to the losses of energy in the generator and motor during the test. By increasing the load on the generator the load on the motor is increased correspondingly, until it is carrying its full-load horsepower output. Meanwhile, from properly connected voltmeters and ammeters, readings of the voltage impressed on the motor, and the current taken by it at different loads are observed. Simultaneously the temperature of different parts of the motor are taken by means of thermometers, which are bound to the machine with tapes or held with gobs of putty. The speed of the machine at different loads is noted. From the readings thus taken, the efficiency of the motor at different loads may be computed and its other characteristics determined. If the efficiency and other performance characteristics of the machine meet the specification, and its temperature does not become greater than the limit specified by the engineering department, the machine is painted and either shipped to the customer or put into stock to await a sale. If it does not “come up” to its specifications, the difficulty must be corrected.