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House electric brownout?

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I suppose that's a way of looking at it but you might be confusing them with universal motors with carbon brushes which aren't harmed by reduced voltages.

Are you familiar with induction motors? If not I suggest you look it up before reading my reply.

https://en.wikipedia.org/wiki/Induction_motor

Induction motors are constant speed devices. The rotor tries to rotate at the same speed as the mains frequency (i.e. achieve synchronous speed) but it never achieves this as the current in the rotor will stop and so will the motor. Instead the motor nearly reaches synchronous speed, the difference between the actual speed and synchronous speed is called the slip; this increases as the load on the motor increases. If the mains voltage is reduced the torque will be reduced dramatically, causing the rotor to slow down, which will also increase slip and the current in the rotor. As the rotor is effectively the secondary of the transformer, the current in the primary will also increase effectively overloading the motor.

This is why normal TRIAC based lamp dimmers can't be used for controlling AC motors (like those used in fish tank pumps).
 
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