Impregnation Methods and Precautions for Explosion Proof Motor Windings

Explosion proof motor is a kind of motor that can be used in flammable and explosive places, and does not generate electric sparks during operation. Explosion-proof motors are mainly used in coal mines, oil and gas, petrochemical and chemical industries. So what is the purpose of dipping paint for explosion proof motor windings? The winding is the most vulnerable part in the explosion-proof motor. In order to improve the moisture resistance, corrosion resistance and insulation strength of the winding, as well as improve the mechanical strength, thermal conductivity, heat dissipation effect and delay aging, the rewound winding must be dipped in paint.

1. Inspection before dipping paint of explosion proof motor windings

(1) Insulation performance inspection: select an insulation resistance meter according to the rated voltage level of the explosion proof VFD. Measure the phase-to-phase and phase-to-ground insulation resistance of explosion proof motors. The measured resistance values should be above 5 megohms for low-voltage explosion-proof motors, otherwise the cause should be checked and effective treatment should be carried out.

(2) Determine the DC resistance of the winding: measure with a multimeter or a DC resistance tester. When a total of 6 lines from the head and tail of the three-phase winding are drawn out, the DC resistance of each item can be measured separately. If it has been connected into a star or triangle, and only 3 outgoing lines are drawn, the resistance of 3 line ends should be measured. When the phase resistance is required, it needs to be converted. Simple conversion of line resistance and phase resistance: When the unbalance of the three line resistances measured is not greater than 2%, the following method can be used to convert the resistance Rn to Rx.

2. The method of dipping paint for explosion proof motor windings

The methods of dipping the VFD frequency converter mainly include pouring, immersion, and vacuum pressure dipping. For a single repaired explosion-proof motor, immersion is mostly used. Immersion and vacuum pressure immersion are usually used to manufacture explosion-proof motors. Immersion is used in mass production of explosion-proof motors, while vacuum pressure immersion is used for high-voltage explosion-proof motors.

3. Precautions for dipping of windings of explosion proof motors

(1) Dip paint temperature: If the temperature is too high, the solvent in the paint will volatilize rapidly, so that the surface of the winding will form a paint film prematurely, and it will not easily penetrate into the inside of the winding. If the effect is not achieved, the material will be wasted; Pre-baking. Practice has proved that the best effect of dipping paint is when the temperature is between 60 and 80 degrees Celsius.

(2) The dipping time of explosion proof motor windings. The principle of choosing the dipping time of explosion proof motor windings is the first dipping. It is hoped that the dipping can penetrate into the winding as much as possible, so the dipping time should be longer, about 15 to 20 minutes. For the second dipping, as long as a good paint film is formed, the dipping time should be shorter, so as not to damage the paint film if the time is too long, so the best time is about 10 to 15 minutes.