The safety of increased safety electrical equipment is largely determined by the temperature at which the equipment is operating. In order to ensure that the electrical equipment does not exceed its limit temperature, it is necessary to add various types of protection control devices to the equipment. There are two kinds of protection devices commonly used in increased safety electrical equipment: one is a power supply protection device, also called an indirect control device, which is composed of a fuse, an air switch and a current limiting relay (thermal relay). The device is connected to the electrical equipment in the same main circuit and is tuned according to the rated current of the electrical equipment (typically 85% of the rated value). When the current of the electrical equipment exceeds the set value, the thermal relay will automatically cut off the circuit to ensure the safety performance of the electrical equipment. The other is a temperature-type protection device (also called direct type), which consists of a heat-sensitive element embedded in the interior of the electrical device and connected to the control circuit of the electrical device through a lead. When the winding temperature of the electrical equipment rises, the resistance value of the thermal element rises rapidly, which is equivalent to being in an open state. At this time, the temperature switch and the intermediate relay act to control the air switch of the main circuit, thereby realizing the protection of the electrical equipment.
Cable and wire connections are present in any electrical equipment. Practice has proved that some explosive accidents are caused by overheating or electric sparks caused by loose connections or poor connections. In order to ensure safe and reliable operation of the increased safety electrical equipment, the connection of the components on the circuit of the increased safety electrical equipment, the connection of the wires and the cables must be firm and safe, and the cable or the wire may not be loose or self-detached due to vibration or the like. It produces overheating or sparking. Therefore, it is convenient to make the wiring when manufacturing the increased safety electrical equipment, the operation is simple, and the connection can be maintained with a certain pressure. Most of the cables and wires of electrical equipment are connected by connectors. The connectors are mainly composed of conductive screws, terminal blocks and other components. In order to ensure the safety performance of the increased safety electrical equipment, some requirements are imposed on the connecting parts: 1 The connecting parts used can not damage the edges and burrs of the cable or the wires, and can not produce permanent deformation and self-rotation during normal tightening, 2 connecting parts The pressure cannot be transmitted by the insulating material member, and the elastic intermediate member (the combination of the spring washer, the flat washer and the nut) must be provided between the conductive member and the insulator member in the connecting member, so as to ensure that the insulating member does not transmit contact. The pressure can ensure the cable or wire connection is firm and reliable, and will not cause contact failure and sparking phenomenon; 3 can not use aluminum material as the connecting piece, because the aluminum material is easily corroded and oxidized, if used as a connector Poor contact, heat generation, etc., resulting in spark formation unsafe factors.
The connectors that meet the requirements are selected, and these connectors should be used correctly to make the connection between the wires and the cables firm and reliable, without overheating, sparking, etc., so that there is no danger of igniting the explosive mixture. Therefore, the correct connection of wires and cables is also an important measure to improve the safety of electrical equipment. The common connection methods for cables and wires for increased safety electrical equipment are as follows: 1 Use bolts or screws with anti-loosening measures. This connection is safe and reliable; 2 mechanically squeeze the parts to be connected (such as using pressure lines) The method of crimping is pressed together by a squeeze connection. This connection method has better electrical conductivity; 3 mechanical connection is connected with the connection of the weld connection. This connection method firstly mechanically connects the components to be connected first. The connection is made so that the connection point has a certain mechanical strength and electrical conductivity, and then the solder is used for welding; 4 the welding connection method of the brazing and the welding, the two welding methods are slightly different in the welding process, and the two The welding connection method does not require other auxiliary connection methods, and the welding connection can be directly performed. These two connections can withstand certain thermal and mechanical stresses, have high mechanical strength and good heat and electrical conductivity. The above several connection methods have their own characteristics, and the appropriate connection method can be selected according to the technical requirements, so that the connection is firm and reliable, and the equipment is safely operated.
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