For the safety of personnel and equipment, the explosion proof motor must be used in hazardous areas. The explosion-proof electric motor is designed for flammable gas, dust, or fiber in hazardous environments. The engine will generate heat under normal working conditions. If the rotor coil fails, sparks may be generated. Suppose certain hazardous substances are present in the environment. In that case, excessive motor housing temperature or failure to properly contain sparks may cause an explosion or fire.
The explosion proof electric motor used in a class I environment (UL name) with combustible gas, steam, or liquid can prevent internal spark or flame from escaping out of the motor and entering the dangerous environment. In addition, such motors can prevent the housing temperature from exceeding the safe temperature in the presence of gas, steam, and liquid.
The explosion proof VFD used in class II or III environment (UL classification) with specific dust or fiber can prevent the motor shell temperature from exceeding the safe temperature of combustible dust and fiber environment. Although reducing the motor's rated current can decrease the heat generated by the motor, there are other fail-safe methods to limit the excessive temperature of the motor housing, including a thermostat that can cut off the power supply to the motor before the motor reaches the critical temperature.
Other technologies can also be used for other equipment operating in these environments. Some technologies can also be used on motors, including ventilation or pressurization, additional explosion-proof housing, packaging, and even liquid filling design. No matter what technology is used, the purpose is to prevent the motor from igniting inflammable under normal working conditions or in case of failure.
The wiring of this electrical transmission equipment shall be in the junction box. The junction box must also be equipped with a rubber sealing ring, JBQ motor outgoing line, and other explosion-proof motor accessories.
Precautions for wiring of explosion-proof motor:
1. Check the electrical clearance, and creepage distance after the junction box is installed: 380 / 660V, the small electrical clearance is 10mm, and the small creepage distance is 18mm. 1140V small electrical clearance is 18mm, and the small creepage distance is 30mm.
2. The incoming line of the junction box is sealed by pressing the rubber ring. The weakness of this structure is the aging and elastic failure of the rubber ring, resulting in inconsistent coordination between the cable and the rubber ring.
3. For the junction box with a double outlet, the unused outlet shall be blocked with a metal seal thickness of no less than 2mm. The outer diameter of the metal seal shall be close to the inner diameter of the outlet hole of the inlet and outlet device to ensure that the pressure plate or compression nut can press the seal ring evenly and tightly to achieve reliable sealing.