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1、 General type certificate of conformity for mining（KYCertification)

Mining general electrical equipment is a type of electrical equipment used in coal mines without any explosion-proof measures and in places where there is no explosive mixture of gas and coal dust. Mining general electrical equipment is different from general electrical equipment in that it has special requirements in insulation, creepage distance, electrical clearance, moisture and dust prevention, and underground operating conditions. There is a clear "KY" mark on the upper right corner of the nameplate.

2、 Technical requirements for general electrical equipment used in mining

1. Has a certain mechanical strength

General electrical equipment for mining mainly includes equipment casing, cable entry devices, wiring terminals, and interlocking mechanisms, in addition to the electrical part. The casing of general electrical equipment used in mining must be made of non combustible or flame-retardant materials, except for observation windows, transparent parts, gaskets, sealing components of cable entry devices, and control handles on the casing. The equipment casing should have a certain mechanical strength and be able to withstand the specified low impact energy impact test. Portable devices should be able to withstand the specified drop test. The casing of general electrical equipment used in mining should have a certain level of protection, generally not lower than IP54. But the protection level at the inlet and outlet of the air-cooled motor fan should not be lower than IP20 and IP10. For equipment used in chambers without dripping water or dust intrusion, starting resistors and rectifier units with a maximum surface temperature below 200 ℃ must have a protection level not lower than IP21. The protection level of equipment without exposed live components, equipment cooled by external fans, and welding rectifiers shall not be lower than IP43.

2. Surface temperature

There are also some special requirements for the surface temperature of general electrical equipment used in mining. The surface temperature of general electrical equipment should not exceed 85 ℃ (except for electric motors and oil immersed transformers). The operating handle and handwheel should not exceed 60 ℃. The parts that can prevent human contact in terms of structure may not exceed 150 ℃.

3. Fasteners

The bolt diameter of all fasteners for the casing of general electrical equipment used in mining should not be less than M6. The fastening bolts of frequently opened lids should be equipped with anti detachment devices. Tightening bolts should be equipped with anti loosening devices such as spring washers.

4. Cable entry device

The cable entry device on the equipment casing must be able to prevent cable twisting, pulling out, and damage. There should be a certain space inside the equipment to ensure that the cable sheath reaches a certain length (8mm). Rubber or other sealing materials should be used to seal the cable entry point to prevent dust or water from seeping into the shell from the cable entry point, ensuring that the shell reaches a certain level of protection. The conductive parts of the wiring terminals introduced by cables should be made of copper or brass to ensure good conductivity. The terminal block should reliably connect the core wire with or without a terminal block. The electrical clearance and creepage distance between the wiring terminals of general electrical equipment for mining and between the wiring terminals and the ground should comply with regulations. For wiring terminals with a voltage higher than 127V, aged and flammable phenolic plastic cannot be used as insulation.

5. Grounding

The casing of general electrical equipment used in mining must have grounding bolts. For portable and mobile electrical equipment, external grounding bolts are not required, but grounding core cables must be used. The grounding bolt should be made of stainless steel material or treated with electroplating rust prevention. The grounding terminal should have a certain mechanical strength and ensure reliable connection. Even if it is affected by temperature changes, vibrations, etc., poor contact should not occur. Each grounding terminal can only be connected to one grounding core wire of the power cable or two grounding core wires of the control cable. The grounding terminals of plastic shells and plastic/metal composite shells should be connected with wires with a cross-sectional area of 6mm2 or more.

6. Warning

In order to ensure the safe operation of electrical equipment and prevent misoperation, all switch handles of general mining electrical equipment must be self-locking after cutting off the power supply. For equipment with a DC voltage higher than 60V and an AC voltage higher than 36V, devices should be installed to prevent live opening of the cover. If this device cannot be set up, a warning sign of "power off and cover opening" should be set up. For equipment with the above voltage levels, if there is a possibility of touching live parts after opening or removing the equipment parts or components, a protective cover with a protection level not lower than IP20 should be installed and a warning sign of "Beware of Electric Shock" should be set up.

7. Other requirements

(1) General electrical equipment used in mining should have moisture resistance and undergo wet heat testing according to regulations. In order to maintain good conductivity, the busbars, control circuits, and auxiliary circuit conductors of the equipment should all be made of copper.

(2) General electrical equipment for mining mainly includes oil immersed transformers, high and low voltage switchgear, control equipment, and plug-in devices. In addition to meeting the requirements of general electrical equipment for mining, they should also meet some special technical requirements.

(3) The special requirements for oil immersed transformers are mainly that the protection level of the outer shell should reach IP44, and there should be an oil gauge on the oil tank of the transformer to display the level of oil inside the shell. In any case, the oil level must be at least 10mm higher than the exposed live parts inside the shell to ensure the safe operation of the transformer. The plug used for draining oil from the lower part of the fuel tank should adopt a special structure, so that it can only be opened with a special tool to prevent the loss of oil in the shell due to arbitrary opening.