Cause Of Excessive Motor Current

- Dec 03, 2018-

Cause of excessive motor current

Motor itself problem

1, motor winding open circuit

When one phase winding in the motor winding is broken, or one branch in the parallel branch is open, the three-phase current will be unbalanced and the motor will overheat.

2, motor winding short circuit

When the motor winding has a short-circuit fault, the short-circuit current is much larger than the normal operating current, which causes the winding copper loss to increase, causing the winding to overheat or even burn out.

3, motor star angle connection error

When the delta connection motor is staggered into a star shape, the motor is still running at full load, the current flowing through the stator winding exceeds the rated current, and even the motor stops by itself. If the stall time is longer and the power is not cut off, the winding is not only serious. Overheating will also burn out. When the star-connected motor is misaligned into a triangle, or a plurality of coils are connected in a branch, the motor is misconnected into two branches in parallel, which will overheat the winding and the core, and will burn the winding in severe cases.

4, motor coil connection error

When a coil, coil set or one-phase winding is reversed, it will cause a serious imbalance of the three-phase current and overheat the winding.

5, the mechanical failure of the motor

When the motor shaft is bent, the assembly is not good, the bearing is faulty, etc., the motor current is increased, the copper loss and the mechanical friction loss are increased, and the motor is overheated.

Ventilation and heat dissipation

1. The ambient temperature is too high, so the inlet air temperature is high.

2. There are debris in the air inlet to block the air, which makes the air intake small.

3. Excessive dust inside the motor affects heat dissipation.

4. The fan is damaged or reversed, resulting in no wind or small air volume.

5, no windshield or motor end cover is not equipped with windshield, resulting in no motor wind path.

other problems

1. Rework motor problem

The motor starting current of the repaired motor is more than 66%, and the motor is frequently operated, which also causes high current and overheating of the motor.

2. Series resistance problem

Wire-wound motors and series resistors do not match, and the motor operates frequently, causing high currents and overheating of the motor.

3. Motor vibration problem

Excessive motor vibration may also cause high motor current, reasons and treatment methods:

1. Rotor imbalance - leveling balance

2, pulley imbalance or shaft extension bending - check and correct

3. The motor is not aligned with the load axis - check the axis of the unit

4, the motor is not properly installed - check the installation and foot screws

5, the load suddenly overweight - reduce the load

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