Identifier: cyclopediaofappl04amer (find matches)
Title: Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc.
Year: 1916 (1910s)
Authors: American Technical Society
Subjects: Electric engineering
Publisher: Chicago : American Technical Society
Contributing Library: Northeastern University, Snell Library
Digitizing Sponsor: Northeastern University, Snell Library

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mum output,varies as the square of the voltage, the results obtained by this testwill not be accurate unless the voltages applied to the stator windingsare kept constantly at normal value. If for any reason it is impos-sible to load the motor to the breakdown point, the voltage may bereduced, and the maximum load at normal voltage may be calcu-lated from the value obtained at the reduced voltage by multiplying , . Til/ normal voltage \^ the observed maximum load by I —-. -. 5 I . \ reduced voltage / If, for example, an induction motor rated at 50 horse-powergives a maximum output of 25 horse-power at one-half its ratedvoltage, its maximum output at normal voltage would be approxi-mately 100 horse-power. The most convenient way to load the motor in the above testis to belt it to a direct-current generator, as previously explained.To determine the output of the induction motor, from observationson the direct-current generator, proceed in the same manner asdescribed under heat run. 426
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ALTERNATING-CURRENT MACHINERY 409 In commercial work it is not customary to run this test to thebreakdown point. The usual method is to find out if the motorwill stand 50 per cent overload without breaking down. When, how-ever, it is desired to obtain a full set of data on a machine, the testis carried to the breakdown point. Starting Torque Test. The stationary or starting torque de-veloped by a motor determines the amount of load under whichit will start. To perform this test a brake is clamped to the pulleyas shown in Fig. 359. A is the center of the pulley; B is the pointof suspension of the brake arm from the spring dynamometer S;C is a reference pointer, carried on a standard, on a horizontal linethrough the center of the pulley. The spring S will measure the

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