Three-phase asynchronous motors are our main products. They are very convenient to use and have been recognized by a large number of customers due to their own advantages. However, when in use, there may be a situation where the windings are connected incorrectly, which will affect our use. How should we solve this problem? Let’s take a look together.

The incorrect connection of the windings in a three-phase asynchronous motor causes an incomplete rotating magnetic field, resulting in symptoms such as difficult starting, unbalanced three-phase current, and high noise. In severe cases, if not dealt with promptly, the windings may be burned out. The main situations are as follows: One or several coils in a certain pole phase are reversed or the heads and tails are connected incorrectly; The pole (phase) group is connected in reverse; A certain phase winding is connected in reverse; The branch connections of the multiple parallel windings are incorrect. The connection of “△” and “Y” is incorrect.

1. Fault phenomenon
The motor cannot start, the no-load current is too large or the imbalance is too large, the temperature rise is too fast or there is severe vibration with a lot of noise, and the fuse is blown, etc.

2. Causes
Mistakenly connecting the “△” type as the “Y” type; During maintenance and repair, one phase of the three-phase winding was connected in reverse. Decompression start-up is caused by inappropriate selection of the tap position or incorrect internal wiring. When the new motor was rolled off the production line, the winding connection was incorrect. The judgment of the old motor’s protrusion is incorrect.

Maintenance method

Ball bearing method. If the balls rotate and roll along the inner circumferential surface of the stator, it indicates that the operation is correct; otherwise, there is a connection error in the windings.

The compass method. If the windings are not connected incorrectly, in a one-phase winding, when the compass passes through adjacent pole (phase) groups, the polarity indicated should be opposite; in a three-phase winding, the pole (phase) groups of adjacent different phases should also be opposite. If the polarity direction remains unchanged, it indicates that one pole (phase) group is connected in reverse. If the direction is uncertain, there are coils connected in reverse within the phase group.

Multimeter voltage method. According to the wiring diagram, if the voltmeter shows no indication in both measurements, or if there is a reading in one measurement and no reading in the other, it indicates that the winding is connected in reverse.

Common methods also include dry battery method, milliammeter residual magnetism method, and motor rotation direction method, etc.

Treatment method

If a coil or coil group is connected in reverse, there will be a significant imbalance in the no-load current, and it should be sent to the factory for repair.

If the lead-out wires are incorrect, the beginning and end should be correctly identified and then reconnected.

If the reduced-voltage start-up connection is incorrect, carefully check and rewire against the wiring diagram or schematic diagram.

If the wiring of a new motor is incorrect after it is taken off the production line or new windings are reconnected, it should be sent to the factory for repair.

When one phase of the stator winding is connected in reverse, the current of the reversed phase is particularly large. Based on this feature, faults can be located and repairs carried out.

If the “Y” type is connected to the “△” type or the number of turns is insufficient, the no-load current will be large and should be corrected in time.

We have already detailed the solution to the problem of incorrect winding connection of a three-phase asynchronous motor in the previous text. When using it, you must pay attention to this aspect. We hope it can be helpful to you.