How to measure the insulation resistance of three-phase asynchronous motor

Take the 380V three-phase asynchronous motor as an example:

1. For the 380V motor, use a 500V or 1000V grade shaker.

2. When measuring, check the electricity. In the case of no power, if there is no electricity, if there is no electricity, the important thing is said three times.

3. Disconnect the connecting piece between the windings, measure the DC resistance of each winding with a multimeter, and check whether the winding is intact.

4. First measure the insulation resistance of the winding to the ground. Before the test, test the integrity of the shaker and do an open circuit and short circuit test. After normal, the L terminal is connected to the winding, the E end is connected to the motor casing, and the shake table is shaken to keep The constant speed is 120r/min. After 1min, the reading is read and the resistance should not be less than 0.5 megohm.

5. Measure the phase-to-phase insulation, connect the L-terminal to a set of windings, and connect E to another set of windings. Shake the table to maintain a constant speed of 120r/min. After 1min, read the reading and the resistance should not be less than 0.5 megohms. Then replace the winding, three windings and two phases.

6. After the measurement is completed, if it is normal, restore the connecting piece and wiring of the motor. If it is not normal, the motor should be restored and insulated, usually by drying or dipping.

Measuring the insulation resistance to ground

Measuring phase-to-phase insulation resistance

PS: Reasons for motor insulation reduction and treatment methods:

(1) The motor winding is damp. Drying treatment should be carried out;

(2) There are too many dust and carbide substances on the windings. Need to eliminate dust;

(3) Poor insulation in the lead wire and the junction box. Should be re-wrapped;

(4) The motor winding is overheated and aged. It should be re-impregnated or re-rolled.