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

General electrical equipment for mining is a type of electrical equipment that has not taken any explosion-proof measures and is used in coal mines without gas or explosive mixtures of coal dust. General mining 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, in addition to the electrical part, mainly includes equipment casings, cable entry devices, wiring terminals, and interlocking mechanisms. The casing of general electrical equipment for mining must be made of non combustible or flame retardant materials, except for the observation windows, transparent parts, gaskets, sealing parts 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 for mining should have a certain level of protection, generally not lower than IP54. However, the protection level at the inlet and outlet of the external air-cooled motor fan shall not be lower than IP20 and IP10. Equipment used in chambers without dripping water and dust intrusion, starting resistors and rectifier units with a maximum surface temperature below 200 ℃, shall 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

The surface temperature of general electrical equipment for mining also has some special requirements. 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 temperature of the parts that can prevent human contact in terms of structure may not exceed 150 ℃.

3. Fasteners

The bolt diameter of all fasteners on the casing of general electrical equipment for mining should not be less than M6. For frequently opened lids, fastening bolts should be equipped with anti falling devices. Tighten bolts 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, and there should be a certain amount of 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 wires with or without terminal blocks. The electrical clearance and creepage distance between the wiring terminals of general mining electrical equipment 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 plastics cannot be used as insulation components.

5. Grounding

The casing of general electrical equipment for 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 undergo electroplating rust prevention treatment. 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 cores 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 at least 6mm2.

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 able to lock themselves after cutting off the power. For equipment with a DC voltage higher than 60V and an AC voltage higher than 36V, a device should be installed to prevent live opening of the cover. If such a device cannot be installed, a warning sign indicating "power off and cover opening" should be set up. For equipment with the above voltage levels, if it is possible to come into contact with live parts after opening the cover or removing the equipment parts or components, a protective cover with a protection level of no less than IP20 should be installed and a warning sign "Be careful of electric shock" should be set up.

7. Other requirements

(1) General electrical equipment used in mining should have moisture resistance and undergo humidity and heat tests according to regulations. In order to maintain good conductivity, the busbars, control circuits, and auxiliary circuit conductors of the equipment should 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. They should not only meet the requirements of general electrical equipment for mining, but also meet some special technical requirements.

(3) The special requirements for oil immersed transformers are mainly that the protection level of the shell should reach IP44, and there should be an oil mark 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 at the bottom of the fuel tank should be of a special structure, so that it can only be opened with special tools to prevent accidental opening and the loss of oil inside the shell.