The national standard of the People's Republic of China, GB/T21707-2018 Insulation Specification for Three Phase Asynchronous Motors for Variable Frequency Speed Control, which our company participated in drafting, was officially implemented on January 1, 2019.
This standard replaces GB/T21707-2008 and provides insulation specifications for three-phase asynchronous motors powered by frequency converters, including terminology and definitions, technical requirements and inspection rules. This standard is applicable to three-phase asynchronous motors specifically designed for variable frequency speed regulation with a rated voltage of 1140V and below.
This standard is formulated by referring to relevant domestic and foreign standards and absorbing the research and production experience of three asynchronous motors with variable frequency speed regulation. It provides clear standards for the general requirements, performance, insulation structure technical requirements, test conditions, and inspection requirements of the electromagnetic wires involved in the production process of the three asynchronous motors with variable frequency speed regulation. The three-phase asynchronous motor variable frequency speed regulation system has excellent speed regulation performance, which can fully leverage the advantages of three-phase cage asynchronous motors, achieve smooth stepless speed regulation, have a wide speed regulation range, and high efficiency. However, the variable frequency system is more complex and costly. This standard helps to control the production cost of three asynchronous motors with variable frequency speed regulation and improve motor stability.