The insulation grade of a motor refers to the heat resistance grade of the insulating material used, which is divided into A, E, B, F, and H grades. The allowable temperature rise refers to the limit of the motor’s temperature increase compared to the ambient temperature.
The insulation grade of a motor refers to the heat resistance grade of the insulating material used, which is divided into A, E, B, F, and H grades. The allowable temperature rise refers to the limit of the temperature rise of the motor compared with the ambient temperature.
Insulation grade of motor
Temperature grade of insulation Grade A Grade E Grade B Grade F Grade H
Maximum allowable temperature (℃) 105 120 130 155 180
Winding temperature rise limit (K) 60 75 80 100 125
Performance reference temperature (℃) 80 95 100 120 145
In electrical equipment such as generators, insulating materials are the weakest link. Insulating materials are particularly susceptible to high temperatures, which accelerate aging and damage. Different insulating materials have different heat resistance properties, and electrical equipment using different insulating materials has different ability to withstand high temperatures. Therefore, general electrical equipment has a maximum operating temperature.
Insulation grade breakdown
People have set 7 maximum allowable temperatures for different insulation materials based on their ability to withstand high temperatures, and they are arranged in order of temperature: Y, A, E, B, F, H and C. Their allowable operating temperatures are: 90, 105, 120, 130, 155, 180 and above 180°C. Therefore, Class B insulation means that the insulation heat resistance temperature of the generator (motor) is 130°C. When the generator is working, the user should ensure that the insulation material of the generator does not exceed this temperature to ensure the normal operation of the generator.
1. Motor insulation design specifications
▶ GB/T 16935.1/IEC 60664-1
Insulation coordination for equipment within low-voltage systems
▶ GB/T 22720.1/IEC 60034-18-41
Rotating electrical machines – Part 18-41: Partial discharge free electrical insulation systems (Type I) used in rotating electrical machines fed from voltage converters – Qualification and quality control tests
▶ GB/T 22720.2/IEC 60034-18-42
Rotating electrical machines – Part 18-42: Partial discharge resistant electrical insulation systems (Type II) used in rotating electrical machines fed from voltage converters – Qualification tests
Summary: These 3 standards apply to the design of electrical clearances, creepage distances, and motor insulation types.
2. Insulation test
▶ GB/T 29311/IEC 61251
Electrical insulating material and systems-AC voltage endurance evaluation
▶ GB/T 20112/IEC 60505
Evaluation and qualification of electrical insulation systems
▶ GB/T 20160-2006
Insulation resistance test of rotating motors
Summary: These are the reference standards for motor insulation testing. Different from 18488, these standards are more detailed and easier to understand the test mechanism.
3. Insulation evaluation
▶ IEEE 1064：
IEEE guide for multifactor stress functional testing of electrical insulation
▶ IEEE 101:
IEEE guide for statustical analysis of termal life test data
▶ IEC 60216-1:
Electrical insulating materials – Thermal endurance properties – Part 1: Ageing procedures and evaluation of test results
▶ IEC 60216-2 :
Electrical insulating materials – Thermal endurance properties – Part 2: Determination of thermal endurance properties of electrical insulating materials – Choice of test criteria
▶ IEC 60216-3：
Electrical insulating materials – Thermal endurance properties – Part 3: Instructions for calculating thermal endurance characteristics
Summary: The above specifications are designed for aging tests, which are mainly used to evaluate the life of electrical insulation.
4. Insulating paper
▶GB/T 5591.1/IEC 60626-1: Combined flexible materials for electrical insulation-Part 1: Definitions and general requirements.
▶GB/T 5591.2/IEC 60626-2: Combined flexible materials for electrical insulation-Part 2: Methods of test.
▶GB/T 5591.3/IEC 60626-3: Combined flexible materials for electrical insulation-Part 3: Specifications for individual material.
▶ GB/T 1408.1/60243-1:
Methods of test for electrical strength of solid insulating materials tests at power frequencies.
5. Enameled wire
▶ GB/T 4074.5/IEC 60851-5: Winding wires test methods-Part 5: Electrical properties.
▶ GB/T 4074.6/IEC 60851-6: Winding wires test methods-Part 6: Thermal properties.
▶ GB/T 4074.21/IEC 60851-21: Winding wires test methods-Part 21: Electrical endurance under high-frequency voltage impulses.
6. Insulating paint
▶ GB/T 15022.1/IEC 60455-1: Resin based reactive compounds used for electrical insulation-Part 1: Definitions and general requirements.
▶ GB/T 15022.2/IEC 60455-2: Resin based reactive compounds used for electrical insulation-Part 2: Methods of test.
▶ GB/T 15022.4/IEC 6045-4:
Resin based reactive compounds used for electrical insulation-Part 4: Unsaturated polyester-based impregnating resins
Summary: 4, 5, 6 are standards related to motor insulation materials. The most important thing for insulation materials is the breakdown field strength, and enameled wires also focus on PDIV and heat resistance.
Selecting the appropriate insulation level can ensure the stability and safety of the motor under specific operating conditions. At the same time, it is also necessary to regularly check during use. The detection and maintenance of insulation resistance ensures the long-term stable operation of the motor.
I hope the above content can provide you with a comprehensive understanding and reference of the motor insulation level.
