Connecting induction motors; the practical application of a designing engineer's experience to the problems of operating engineers, armature winders ... questions arising in winding and connecting - Softcover
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 Excerpt: ...where the frequency is changed and the number of poles remains the same. The resulting change in the speed in this case is assumed to be proper for the motor in question, and the gears or pulleys are changed so that the driven load will operate at the same speed. Relation between Voltage and Frequency. The next thing that is affected by the change in frequency is the operating voltage. That is to say, if the frequency is raised, the voltage should be raised also and vice versa, if the conditions in the magnetic and electric circuits are to be kept normal. Assuming that the rotating magnetic field is to be kept at the same value and the frequency raised, this field will rotate at a faster rate and cut more conductors in a given time, which will immediately result in the generation of more voltage, or counterelectromotive force as it is called in a motor. It will be remembered that in the first chapter attention was called to the fact that one of the easiest ways of thinking of an induction motor is as an alternating-current generator generating a counterelectromotive force almost exactly equal to the line voltage on which it is operated. In the present instance, then, if raising the frequency causes the motor to generate more of this back voltage, it will be necessary to oppose it by a higher applied voltage; or, speaking simply, if the frequency is to be raised the line voltage should be raised by the same amount to keep the same magnetic conditions as existed in the original motor. Relation between Torque, R.P.M., and Horsepower. Suppose that the frequency is raised and the voltage is not raised. If the same magnetic field existed and rotated faster, it has been shown that an increased back voltage would be generated. However, if the line voltage is not ra...
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- PublisherRarebooksclub.com
- Publication date2012
- ISBN 10 1231272325
- ISBN 13 9781231272329
- BindingPaperback
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