Starting a three-phase motor without phase shifters. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Starting a three-phase motor without phase shifters. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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The proposed method is not new, but rather a well-forgotten old one, and consists in the fact that to start the engine, its shaft is untwisted in the working direction. The low power motor is easy to start by turning the shaft by hand. A cord is wound around the shaft of a high-power motor, pulling on which gives it rotation.

Despite the simplicity, this method has its advantages: no additional devices are required (except for a cord for a powerful engine), the direction of rotation can be any. But in this case, it should be borne in mind that if the engine operates without phase shifters at all, its useful shaft power is reduced. In addition, when overloaded, the engine stops and it needs to be restarted, which limits the scope of the proposed method.

However, at home, a small fan at the workplace, a sharpening machine for straightening household cutting tools (grindstone) work successfully with such a launch. If you need to check a powerful electric motor, but there is no three-phase network, then this option will suit you. Minute business. In this case, the motor with short-circuited coils will not start in this way. To reduce the starting current of powerful machines, you must first pull the rope and, without yawning, apply power.

So you can start both low-speed and high-speed engines, and load only after starting.

Quite often, when a starting capacitor with a capacity selected at the rate of 1 μF per 10 W of power is turned on, a low-speed motor overheats even at idle. In this case, the capacitance of the capacitor has to be reduced so much that its efficiency becomes barely perceptible. In such a situation, the proposed method also justifies itself.

Author: V.M. Paley

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