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What would happen when an alternating current (AC) is passed to a DC motor? And a direct current (DC) passed to an AC motor? Will it work or not? What will happen to it?

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up vote 2 down vote accepted

It depends on the construction of the motor. If the field winding is connected in series with the armature winding, the motor is like a universal motor and will probably operate normally. A universal motor is similar to a DC motor with the armature connected in series with the field. If DC is supplied it works like any DC series motor. If AC is supplied, the stator and rotor field strengths will vary exactly in phase with each other. When the AC current changes direction, the stator and rotor fields will reverse at the exact same instant. Therefore, the torque will always be in the same direction even though the fields change direction because the stator and rotor fields always have the same relationship with each other. When connected to AC, torque magnitude pulses at twice the line frequency.

But if the field winding is connected in parallel with the armature, the motor will not run, but will draw current, make noise and get hot. It is like the torque for such a small time(half time period for AC) cannot produce much torque and in the next half the torque is reversed in direction.

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