Tapping field speed control method is used in a/an ______ for speed control.

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SSC JE Electrical 15 Nov 2022 Shift 2 Official Paper

Answer 1

Speed control methods of universal motor

1.) Field Tapping Method

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In this method, the field poles are tapped at various points so that the speed of the motor can be varied by varying the field strength.
If there are more tapping from the field, then we can have various speeds for the motor.
For this purpose of speed setting, the field poles are wound in various sections with different series of wire and taps are brought out from each section.

2.) Centrifugal Mechanism

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If the motor speed rises above that set by the lever, the centrifugal device or switch opens two contacts and inserts a resistance R in the power circuit to the motor, which causes the motor speed to decrease.
If the motor runs too slowly, the centrifugal device will close the two contacts and short circuit the resistance so that the motor speed rises.
A resistance is connected across the centrifugal switch or device to perform this function. A capacitor C is used across the contact points in order to reduce sparking produced due to the opening and closing of these points.

3.) Resistance Method

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In this method, the speed of the electric motor is controlled or set by connecting a variable resistance R in series with the motor.
Due to having the resistance before the motor, the current to the motor is reduced, which in turns reduces the speed of the motor according to the setting of that variable resistance.