How to judge whether the motor is burnt out or not when it is overheated

Update:03-04-2019
Summary:

Common causes of overheating:   1. Motor overload, […]

Common causes of overheating:

 

1. Motor overload, overload operation.

2. The motor has been running without phase.

3. The power supply voltage is too high or too low! Over the range of motor voltage allowed to change!

4. The connection of motor winding is wrong.

5. Start the motor very frequently!

 

Motor overheating does not necessarily burn out, because motors are generally equipped with comprehensive motor protectors, can be overloaded, overload in time to disconnect the circuit to protect the motor. The worst should also have a thermal relay to protect the motor, overload operation will cut off the circuit, protect the motor, so motor overheating will not necessarily be burned out!

 

Two commonly used judging methods for burning out of three-phase asynchronous motors are as follows:

 

Ⅰ.Insulation shake table measurement.

1. Select the appropriate insulation shake table 500 megaohms or 1000 megaohms, respectively, three-phase winding A phase, B phase, C phase and the insulation resistance between the ground shell, shake the insulation shake table evenly, the insulation resistance value of each phase measured by the insulation shake table is not less than 0.5 megaohms before it is normal.

 

2. Measuring any two phases of phase A, B and C with an insulating shaker. When shaking uniformly, the resistance values of any two phases are near zero under normal conditions, and the resistance values of any two phases are almost the same.

 

II.The multimeter is roughly measured.

1. Measure the three windings of three-phase asynchronous motor to see if there is resistance and whether the resistance value is the same.

Generally, the resistance value of three windings is about the same. The closer the winding is, the better. The resistance value of the winding is related to the power of the motor. The larger the general power, the smaller the resistance. The buzzer of the multimeter sometimes rings.

2. Multimeter resistance high-grade, and then measure whether there is resistance between winding and motor housing. In theory, the resistance between winding and motor housing is close to infinity before good insulation! At least the insulation resistance is above 0.5 megaohms!

 

III. The multimeter and insulation shaker are used to measure the resistance between phases and compare them. The insulation shaker is used to measure the relative ground resistance of any phase and the insulation resistance between phases.