What are the five reasons for high no-load current after ABB motor maintenance

Date:2021-05-27 16:32:16

1. The number of turns in the winding decreases or the pitch of the coil becomes smaller
After ABB motor maintenance, the magnetic induction intensity increases with the decrease of coil turns, and the iron loss is proportional to the square of the magnetic induction intensity, with a significant increase in iron loss. The smaller the pitch of the coil, the smaller the short distance coefficient of the winding, the lower the effective number of turns of the motor, the greater the iron loss, and the greater the no-load current.

2. Improper installation of the motor rotor can result in uneven air gap, or bending of the shaft, bearing failure, etc., all of which can increase the no-load current.
After ABB motor maintenance, the power factor of the motor decreases as the no-load current increases. When the rated voltage and rated current of the motor remain constant, the output power of the motor decreases with the decrease of power factor. If the motor operates at rated load, it will generate heat due to excessive current.

3. Increase in air gap

After ABB motor maintenance, the rotor of the motor rotates for a long time in ventilated air containing certain impurities, resulting in wear from impurities and dust in the air, but the air gap increases. The open motor operated by metallurgical enterprises has been running for more than 10 years, and the air gap has increased by about 15%. Motor hole scanning or iron core eccentricity, during maintenance, the air gap is increased by rotating the rotor.

4. Increased iron core loss
When repairing ABB motors, uneven slots affect wire embedding. Using coarse files to file large slots can cause short circuits in the slot iron core punch, increase the slot size, and increase the effective air gap of the motor; The iron core is corroded and rusted in a humid environment for a long time. When dismantling the winding of an electric motor, incorrect methods such as burning the iron core with fire were used, which caused corrosion of the insulation of the iron core laminations and short circuits between them.
5. Winding wiring error
If a 1y connection error is converted to a 1-connection, a 1-way error is converted to a 2-connection, and so on. Misconnecting Line 1 is equivalent to reducing the number of turns in the single-phase winding by three times, while misconnecting Line 2 is equivalent to reducing the number of turns in the single-phase winding by 50%, resulting in a significant increase in no-load current.