What is the effect of unbalanced voltage?

Vibration of Motor: The negative-sequence voltage caused by voltage imbalance produces opposite torque and leads to motor vibration and noise. Severe voltage imbalance may even result in motor collapse. Reduce Motor Life: Heat generated by Unbalance Voltage may also reduce the Motor life.

What is the effect of voltage variation on a three-phase induction motor?

If variation in both voltage and frequency occur simultaneously, the effect will be superimposed. Thus, if the voltage is high and the frequency low, the locked-rotor torque will be greatly increased, but the power factor will be decreased and the temperature rise increased with normal load.

What happen if three-phase power unbalanced?

Phase unbalance of a three-phase system exists when one or more of the line-to-line voltages in a three-phase system are mismatched. The unbalanced voltages cause unbalanced current in the motor windings; unbalanced currents mean an increase of current to at least one winding raising that winding temperature.

When and unbalanced supply given to an induction motor it will cause effect on?

Effects of unbalance: 2. In induction motors connected to unbalanced supply, the negative sequence currents flow along with positive sequence current resulting in decreased percentage of productive current and poor motor efficiency. Any unbalance above 3\% hampers the motor efficiency.

What is unbalance voltage?

Voltage unbalance occurs when the RMS line voltages on a poly-phase system are unequal. Voltages are seldom perfectly balanced between phases, but when this unbalance becomes excessive, it can create problems for poly-phase motors.

How does voltage affect induction motor speed?

With constant supply power frequency, higher voltage causes higher V/Hz ratio and higher flux. During motor acceleration to synchronous speed (synchronous motors) or close to synchronous speed (induction motors), the current would initially rise to multiple times the rated current and cause voltage drop.

What is the maximum voltage unbalance of a 3 phase motor?

Voltage unbalance exceeding more than 2 percent in three-phase systems can cause current unbalance among the windings. These, in turn, can cause an increase in winding temperature and an overheating problem that can be harmful to the motor.