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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mers are to be used with other apparatusfor which an over-load capacity in excess of 25 per cent is guaranteed,the same guarantee should apply to the transformers. Abnormal Conditions of Operation. Transformers are fre-quently used under conditions departing more or less widely fromthe conditions specified by the manufacturer in regard to values ofprimary and secondary voltages, frequency, and current output.Thus, if a transformer is used with a primary applied voltage inexcess of the rated value (frequency being unchanged), the coreflux will be increased according to equation (34) and the core losseswill be increased according to equations (35) and (36). If, on the other hand, a transformer is used with a frequencyless than the rated frequency (the voltage applied to the primarybeing unchanged), the core flux will be increased according to equa-tion (34), and the hysteresis loss in the core will be increased accordingto equation (35); whereas, the eddy-current loss is un changed. 282
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ALTERNATING-CURRENT MACHINERY 269 The increase of core loss due to increase of primary appliedvoltage, or to decrease of frequency, or to both, may be compen-sated for by reducing the allowable current output, and therebyreducing the copper loss, in order that the total heating of the trans-former may not exceed the normal amount. Examples. A given transformer is rated at 5 kilowatts, and is designedto take current from 1,100-volt mains at a frequency of 60 cycles per second.Under these conditions hysteresis loss Wh, eddy current loss We, and copperloss IFc, will be called normal. (a) The transformer is loaded so that the output is 6 kilowatts at therated electromotive force and frequency. Find Wc in terms of normal. (b) The transformer is used at rated electromotive force, but at afrequency of 75 cycles per second. Find Wh and Wg each in terms of normal. (c) The transformer is used at rated frequency, but with primaryelectromotive force of 1,500 volts. Find Wu and W^ each in terms of

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