How to determine if a three-phase motor has burned out

How to determine if a three-phase motor has burned out

To determine whether a three-phase motor has burned out, the following methods can be used:

Observation method:

Smoke or burnt smell: If the three-phase motor in operation emits smoke or burnt smell, it can be preliminarily judged that the motor is burnt out.

Abnormal temperature rise: If the temperature of the motor increases beyond the specified value during operation, accompanied by noise, severe vibration, slow speed, and control switch tripping, it may cause the motor to be burned out.

Resistance measurement method:

Measuring resistance with a multimeter:

Disconnect the motor power supply and use a multimeter to measure the resistance between the motor leads and the housing. If the resistance value is only a few thousand ohms or less, it indicates that the motor has burned out.

Measure the resistance values of the three wiring terminals of the motor with a multimeter in low resistance mode to see if they are balanced. If they are not balanced, it indicates that the motor is burning.

Use a multimeter to measure the resistance of the two windings in one ohm range. If the resistance is particularly small and close to zero, it can be determined that they have been burned out.

Measure the resistance between each winding and the casing separately using a 10k ohm range. If the resistance is small and close to zero, it can also be judged as burnt out.

Measuring insulation with a megohmmeter:

Use a megohmmeter to measure the insulation resistance between any two windings. If the insulation resistance is found to be low during measurement, it indicates that there is a suspicion of burnout or short circuit in these two windings.

Measure the ground resistance and phase resistance with a 500V megohmmeter, and the minimum resistance value for these two items should not be less than 0.5 megohms. If the measured phase to phase and ground resistance values are above 0.5 megaohms, the motor can be put into operation; otherwise, it cannot be put into operation.

Current measurement method:

Measure the current of a three-phase motor with a multimeter. If the three-phase current imbalance rate is greater than 10%, it may indicate that the motor is burnt out.

Other methods:

Measuring DC resistance with an electric bridge: Use an electric bridge to measure DC resistance, with a three-phase imbalance rate not exceeding 2%. If one pair of resistors is found to have a significant deviation, it may be due to the motor burning out.

Observing the winding condition: If obvious erosion, disconnection or insulation damage is found in the motor winding, it can also be judged that the motor has been burned out.

suggestion

Before conducting any measurements, it is essential to ensure that the motor is completely powered off to avoid the risk of electric shock.

If you are not familiar with the internal structure of the motor, it is recommended to have professional maintenance personnel inspect and judge it.

Regular maintenance and inspection of the motor, timely detection and handling of potential problems, can avoid the risk of motor burnout.