capacitor as filter???

[regs09]

What are the other functions of the capacitor of an induction motor, aside from being a starting and running cap.? Could it be a filter at the same tim, that can filter fluctuations and protect the motor from being burned?

 

[electricpete]

Sometimes surge capacitors are connected line to ground at motor terminals.

Sometimes a partial discharge coupling capacitor is connected line to ground at medium voltage motor terminals for purpose of on-line sensing of partial discharge activity (for example Iris equipment).

Sometimes power factor correction capacitors are provided at various locaitons.



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[waross]

Most single phase capacitor start motors take the capacitor out of the circuit once the motor has started.
Refrigeration compressors are an exception. Many have a run capacitor on-line all the time. This is for power factor correction. It reduces the current drawn and as a result reduces voltage drop with the result that a higher voltage is available at the motor terminals.
Most three phase motors use capacitors for power factor correction.
Medium voltage motors may have capacitors applied to the motor terminals to absorb lightning induced voltage surges. This may be in addition to plant wide PF correction.
The action of a capacitor on AC is not the same as the action of a smoothing capacitor on a DC power supply.

Bill
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