Mining electrical equipment is a non explosion-proof general electrical equipment specially produced for the underground conditions of coal mine. It is suitable for various electrical equipment in the mine conditions, such as mining transformer, motor, switchgear, lighting, communication, signal, control and detection devices, etc. The underground space is narrow, the environment is humid, the dust content is large, there are often rocks and minerals falling; some exist the risk of explosion of biogas (gas), mineral dust, and some are corrosive mineral water and mould parasitism. Therefore, the special requirements of moisture-proof, dust-proof and explosion-proof should be considered in the material and structure of mining electrical equipment.
General electrical equipment for mining is marked Ky. The features are: solid shell structure, good moisture-proof and dust-proof performance, large air gap and leakage distance between internal conductors, mechanical interlocking device on the door cover, which can only be opened when the equipment is powered off to prevent electric shock. This type of equipment can only be used in the mine without gas, coal dust explosion or in the mine without gas outburst.
Mine explosion-proof electrical equipment includes explosion-proof type, intrinsically safe type, increased safety type, oil filled type, positive pressure type, explosion-proof special type and above-mentioned composite type equipment.
The mark of flameproof electrical equipment is KB. It first appeared in Germany at the beginning of the 20th century and is now widely used in many countries. Its principle is based on gap explosion-proof. In addition to meeting the requirements of general electrical equipment for mining, the material and strength of its shell, gap width, length and processing finish of explosion-proof joint surface are strictly regulated. The shell not only bears the maximum pressure that may be generated by the combustible mixture inside the shell, but also gradually cools the explosive product and flame when they are transmitted outward through the joint face, so as not to ignite the combustible mixture outside the shell. It is suitable for places prone to gas and coal dust explosion.
Intrinsically safe electrical equipment is marked Kh. Formerly known as the safe spark type, it first appeared in Britain. In 1939, there were regulations on the manufacture of intrinsically safe electrical equipment. The principle is to select proper electrical parameters so that the electric spark and thermal effect produced by the electrical circuit in normal operation or specified fault state will not ignite the explosive mixture. This kind of equipment does not need flameproof shell, and can be used in the environment with frequent explosion hazard. However, limited by the minimum ignition energy, it can only be used in communication, signal, instrument and control loop.
The increased safety electrical equipment is marked Ka. Super originated from Germany, once known as safety type or explosion-proof safety type. On the electrical equipment without arc, spark or dangerous temperature during normal operation, measures shall be taken to improve the safety level, prevent internal short circuit and ground fault, strictly control the surface temperature of the shell to achieve explosion-proof purpose. This type of equipment does not need bulky flameproof shell, with low cost and easy maintenance. It has been widely used in squirrel cage motors, lighting fixtures, junction boxes and other equipment in Federal Germany, and is rarely used in China at present.
The mark of oil filled electrical equipment is KC. Immerse the live parts that may produce sparks, electric arcs or dangerous temperatures in the oil so that they do not contact with the explosive mixture on the oil surface to prevent ignition and detonation. This type of equipment is only suitable for fixed electrical equipment installed in the same room with fire protection measures, such as AC circuit breaker and transformer.
Positive pressure electrical equipment is marked KF. Electrical equipment with positive pressure fresh air or inert gas filled into the sealed shell to keep a certain positive pressure to prevent the explosive mixture outside the shell from entering. This type belongs to the explosion-proof type of chemical plant, which is not used in coal mine.
The mark of explosion-proof special electrical equipment is KT. The structure does not belong to the above regulations, but other explosion-proof equipment, such as mesh cover or micro hole explosion-proof structure with good corrosion resistance and flame resistance. Different parts of the compound explosion-proof electrical equipment belong to different explosion-proof electrical equipment, such as an explosion-proof magnetic starter, whose control circuit can be intrinsically safe, which is called explosion-proof and intrinsically safe.
All mining electrical equipment must be inspected by the inspection agency designated by the state in accordance with the requirements of relevant regulations, and only after it is qualified can it be used underground.