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If the speed of the rotating magnetic field is equal to the frequency of exerted current,...

If the speed of the rotating magnetic field is equal to the frequency of exerted current, what do you recommend for “braking” of an AC machine if it is used as an electrical motor. What is the normalized amplitude of the resultant magnetic field relative to the magnetic field’s amplitude of each phase?

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Answer #1

In ac machines, speed is directly proprtional to the frequency.

For braking of an AC machine, Dynamic braking can be used for braking. By reconnecting a running motor to act as generator once it is turned off which rapidly stop the motor. The generator action converts the mechanical energy of rotation to electrical energy that can be dissipated as heat in a resistor.

The armature terminals of the DC motor are disconnected from the power supply and immediately connected across a resistor, which acts as a load. The smaller the resistance of the resistor, the greater the rate of energy dissipation and the faster the motor slows down.

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