GB/T 22713-2008Effects of unbalanced voltages on the performance of three-phase cage induction motor (English PDF)

3.1 Current

Negative sequence voltage imbalance produces a rotation of the rotor in the opposite direction of the magnetic field in the motor air gap. Small negative sequence voltage Components may make the current flowing through the winding voltage much larger than the current equilibrium. Flowing through the rotor cage bars current rated frequency is almost Frequency of 2 times, so squish effect squirrel cage rotor bar current loss is increased so that the value of the rotor winding is larger than the value of the stator winding losses increase a lot of.

Unbalanced voltage at the motor rated speed operation, the current imbalance in the degree of large, about six times the voltage unbalance degree ~ 10 times.

Voltage unbalance, locked rotor current unbalanced degree of voltage unbalance degree of the same, but stall the apparent value of the power increase is small.

3.2 Fever

The motor runs at a voltage imbalance, since the current and voltage in the negative sequence component of the stator caused loss increases, so the stator windings Temperature rise than in the equilibrium temperature rise Voltage runtime.

The degree of increase in losses due to the rotor squish effect of current and increased.

In addition, the voltage imbalance is usually associated with reduced voltage sequence components related to Chiang Kai-shek, Chiang Kai-shek rotor which makes the current sequence component increases.

3.3 Torque

When the voltage unbalance, stall torque, minimum torque and maximum torque decrease. If the voltage imbalance is very serious, the motor can not it can operate normally.

Voltage unbalance and frequency of twice the frequency of the oscillation of torque generated about. Increases torque oscillation amplitude of the voltage sequence components and Chiang Kai-shek 25% of the range. When the oscillation frequency torsional torque is nearly 2 times the critical frequency, the entire shafting torsional vibration may cause impermissible.

3.4 Full speed

When the motor is running at full voltage unbalance, because the rotor slip with an additional increase in loss increases, and thus the speed at this time Slightly decreased.