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Precautions When Wiring Explosion-Proof Motors

Dec. 26, 2019

Explosion-proof motor is a type 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.

Explosion-proof motor wiring should be in a special junction box. The junction box must also be equipped with rubber seals, JBQ motor lead-out wires and other special explosion-proof motor accessories.

 

Explosion-Proof Wiring Box

Explosion-Proof Wiring Box

Precautions when wiring explosion-proof motors:

1. Check the electrical clearance and creepage distance after the explosion-proof wiring box  is installed: The minimum electrical clearance of 380 / 660V is 10mm, and the minimum creepage distance is 18mm. The minimum electrical clearance of 1140V is 18mm, and the minimum creepage distance is 30mm.

2. The entry of the junction box is sealed by pressing the rubber ring. The weakness of this structure is the aging of the rubber ring and the elastic failure, which makes the coordination of the cable and the rubber ring inconsistent.

3. For the junction box with double outlets, the unused outlets should be blocked with metal seals with a thickness of not less than 2mm. The outer diameter of the metal seals should be similar to the inner diameter of the outlet holes of the inlet and outlet devices to ensure the pressure plate or pressure The tight nut presses the sealing ring evenly to achieve a reliable seal.

One of the main causes of various failures of explosion-proof motors is damp insulation. For example: In the Lviv-Volensk coal mine, a motor for palm scraper conveyors with a production capacity of more than 1,000 tons a day and night, due to moisture and water droplets in the inner cavity of the motor, the failure of the stator winding insulation resistance is faulty 45.7% of the total.

Therefore, the explosion-proof electrical apparatus of the enclosed structure is not enough to protect it from adverse climatic factors in many cases. Therefore, there should be some special devices in the enclosure of electrical equipment to ensure that climatic conditions are improved. It must include an air humidity adjustment device. This device is used to reduce the relative humidity and humidity of the air in the casing. Occasionally falling water is removed from the casing and prevents the moisture from being sucked in through the bearings and seals.

Precautions for use and maintenance

(1) Care should be taken to select the type of explosion-proof motor according to the use environment.

(2) Short-circuit, overload, overheating, and lack of protection shall be set strictly according to requirements, and these protection devices shall be checked regularly to ensure their effectiveness.

(3) Non-professionals are strictly prohibited from disassembling or repairing any part of the motor.

(4) Connect the power cord according to the following procedure: After removing the terminal box cover, unscrew the terminal bucket, take out the rubber gasket in the wire inlet of the terminal block, and put these two parts on the cable.

The thread type cable gland is introduced into the box from the junction box inlet, and the three core wires are respectively wound on their respective terminals (mining motors also need to wind the ground core wires on the ground screws). Each core wire must be round. Lay the ground in two bow washers and tighten the terminal nut.

(5) If disassembly is required, special attention should be paid to protecting the flameproof surface and windings from being hit. If multiple units are disassembled at the same time, the removed parts should be stored separately and not allowed to be mixed. If the removed parts will be left for a period of time, the anti-explosion surface shall be subject to the necessary anti-rust treatment.