A 3 kW three-phase motor generates heat after running for a while. What is the reason?
A 3KW 380V three-phase asynchronous motor generates severe heat after running for a while. Is it due to a wiring error?

Reverse connection of winding ends:
(U1/V1/W1 short circuit, W2/U2/V2 connected to power supply) belongs to non-standard star connection method. Although theoretically still forming a star shape, it may lead to:

The three-phase magnetic field is unbalanced, resulting in eddy current losses.

Correct connection method: The tail end (W2/U2/V2) of the winding should be short circuited, and the head end (U1/V1/W1) should be connected to the power supply.

Verification method: Disconnect the connecting piece, use a multimeter or battery+pointer meter to confirm the winding ends, and reconnect according to the standard connection method.

The power supply voltage does not match the connection method

Three phase 380V power supply: The star connection method must be used (the voltage loaded on each phase winding is 220V).

Three phase 220V power supply: needs to be changed to a delta connection (with each phase winding still loaded with 220V voltage). If the star connection method is misused, the winding voltage will only be 127V, causing the motor to run under load, increase current, and generate heat.

Inspection steps: Use a multimeter to measure the power supply voltage, confirm whether it is 380V or 220V, and verify the rated voltage on the motor nameplate.

Power issue: Three phase imbalance or phase loss

Even if the voltage is normal, if the three-phase current deviation is greater than 10%, it will cause severe heating.

Detection method: Measure the three-phase current with a clamp meter and observe whether it is balanced. When there is a phase loss, the motor will make a buzzing noise and quickly heat up.

Voltage abnormality: High voltage (>400V) or low voltage (<360V) can cause the winding to overheat.

Suggestion: Measure the voltage fluctuation range under no-load and load conditions.

Mechanical or load issues

If the load power is greater than 3KW (such as pump or fan impeller blockage), the motor will generate heat due to current exceeding the limit.

Troubleshooting: Measure whether the operating current exceeds the rated value (3KW/380V star connection rated current of about 6A).

Bearing damage or poor lubrication

The increase in mechanical friction leads to the conduction of temperature rise to the winding.

Check: Listen for abnormal noise from the bearings and manually rotate the shaft to ensure smooth operation.

Motor malfunction: winding short circuit or insulation aging

Interturn short circuit causes local overheating.

Detection: Observe whether there are any burnt black marks or poor heat dissipation in the winding

If the above five situations cannot be solved, it is necessary to consider replacing the motor or professional maintenance. I hope these analyses can help you!