Why is it that variation allowed in supply voltage to motors is (+ or -)10 %,

Why is it that variation allowed in supply voltage to
motors is (+ or -)10 %, whereas that in frequency is (+ or -
)5 %

Question Posted / shyamalmandirwala

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Why is it that variation allowed in supply voltage to motors is (+ or -)10 %, whereas that in freq..

Answer / gajendran.al

Variation in supply voltage to motor affects the torque
produced by the motor and is not affected much with +/- 10%
whereas variation in frequency affects the speed of the
motor. Even 1Hz variation could vary speed by 30 rpm for a
4 pole motor. So variation in frequency is not advisable in
motor
Pl note that increase in supply frequency makes the motor
rotate above rated speed which may cause mechanical failure
of motor.

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Why is it that variation allowed in supply voltage to motors is (+ or -)10 %, whereas that in freq..

Answer / subash

But in motors the rated frequence +or- 5% will be there its
true

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Why is it that variation allowed in supply voltage to motors is (+ or -)10 %, whereas that in freq..

Answer / shriram.....

For the motor we are not using ups power supply

In ups power supply, we can maintain the voltage as well as
frequency.

But we are using raw power for motors in plants.

Eg if I we are using some load. Now I getting 415 volts at
full load if I reduce some load any reasons then voltage
will lightly increase so voltage will not stay constant.

For that reasons operating voltage +/- 10 %

Shriram....

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