Average

Example—With voltages of 220, 215 and 210, the average is 215, the maximum deviation from the average is 5

PERCENT VOLTAGE UNBALANCE = 100 * 5/215 = 2.3 PERCENT

The locked-rotor torque and breakdown torque are decreased when the voltage is unbalanced. If the voltage unbalance is extremely severe, the torque might not be adequate for the application.

The full-load speed is reduced slightly when the motor operates at unbalanced voltages.

The locked-rotor current will be unbalanced but the locked rotor kVA will increase only slightly.

The currents at normal operating speed with unbalanced voltages will be greatly unbalanced in the order of 6 to 10 times the voltage unbalance.

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