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WindingsforIncreasedSafetyElectricalEquipment|TechnicalSpecifications

Technical Specifications

Windings for Increased Safety Electrical Equipment

In enhanced-safety electrical equipment, such as explosion-proof motors, transformers, electromagnetic wires, and ballasts for fluorescent lamps, a portion includes internal windings. The requirements for these windings, both mechanically and electrically, are higher than those for standard windings.


Generally, the insulated wire used for winding these coils should be double-insulated, and the coil’s rated diameter must not be less than 0.25mm.

For the enameled wire used in winding these coils, it is recommended to use GB/T6109.2-2008 “Polyester Enameled Round Copper Wire, Class 155,” GB/T 6109.5-2008 “Polyester-imide Enameled Round Copper Wire, Class 180,” GB/T 6109.6-2008 “Polyimide Enameled Round Copper Wire, Class 220,” or GB/T6109.20-2008 “Polyamide-imide Composite Polyester or Polyester-imide Enameled Round Copper Wire, Class 220.”

Additionally, Grade 1 enameled round copper wire as specified in these standards can be used, provided it passes the relevant tests outlined in the standards.

After winding, an appropriate impregnating agent should be used to enhance the insulation properties of the windings.

The impregnation process should follow the manufacturer’s specified method, using techniques like dipping, trickling, or vacuum pressure impregnation (VPI) to fill the gaps between winding wires and ensure strong adhesion. If the impregnating agent contains solvents, the impregnation and drying should be performed twice to allow solvent evaporation.

Generally, methods like spraying or coating for insulating windings are considered unreliable for explosion-proof electrical equipment. Adequate attention should be given to this in engineering practice.

Moreover, for high-voltage windings, the impregnated windings should be treated with anti-corona paint to prevent additional hazards caused by corona discharges.

In enhanced-safety electrical devices, whether motors, electromagnetic coils, or other equipment’s coils, they should generally be equipped with temperature protection devices to prevent exceeding limit temperatures under normal operation or recognized abnormal conditions.

If a winding does not exceed the limit temperature under continuous overload (such as a motor rotor lock), or if a winding is not subject to overload (like a ballast for fluorescent lamps), then it does not require a temperature protection device.

When enhanced-safety electrical equipment is equipped with temperature protection devices, these can be installed either internally or externally. Regardless, the protection device should have the appropriate explosion-proof type and should be assessed in conjunction with the protected equipment.

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