[Performance and Numbering Rules of Motor Insulation Materials] The reliability and service life of winding operation largely depend on the performance of the insulation materials. The basic requirements for insulation material performance include electrical performance, heat resistance, and mechanical performance. In a previous post, Ms. Can gave a brief introduction to the electrical performance of insulation materials. Today, we will summarize their heat resistance and mechanical properties and briefly introduce their numbering rules.
Heat resistance of insulating materials
Since motors inevitably generate heat due to losses during operation, the insulation materials used must possess excellent heat resistance. The heat resistance of the insulation material directly determines the allowable temperature rise of the motor. Insulation materials are classified into seven grades based on their heat resistance, each corresponding to a specific limit operating temperature below which the insulation material can be used for a long time without affecting its performance. Furthermore, the insulation material should also have good thermal conductivity and a large heat capacity. For large motor coils, it is often desirable for the coefficient of linear expansion of the insulation material to be close to that of the conductive material to prevent insulation breakage during thermal expansion and contraction.
Mechanical properties of insulating materials
During the wrapping, forming, and disassembly processes of coils and windings, as well as during motor operation, their insulation is subjected to various mechanical stresses. Therefore, corresponding mechanical performance requirements are imposed on the insulation materials, such as tensile strength, compressive strength, bending strength, shear strength, and impact strength. If the mechanical properties of the insulation material are poor, its electrical performance can easily deteriorate significantly due to mechanical forces. Other requirements also apply to insulation materials, such as low hygroscopicity; good resistance to acids, alkalis, and oils; absence of acidic or other easily ionized substances; and ease of processing.
Commonly used insulating materials
Insulating materials can be classified into organic and inorganic materials according to their chemical composition. Organic insulating materials are the most widely used; inorganic insulating materials, such as mica, glass, and asbestos, are generally used in combination with organic insulating materials to overcome their mechanical weaknesses.
Example of material numbering rules
For ease of management and selection, various insulating materials are uniformly numbered, such as 1032, 2432, 3280, etc. The meaning of the four digits is as follows:
The first digit indicates the classification of the insulating material. 1 - Indicates insulating varnishes, resins, and adhesives; 2 - Indicates insulating impregnated fibers; 3 - Indicates insulating laminates; 4 - Indicates insulating pressed plastics; 5 - Indicates insulating mica products.
The second digit indicates different varieties of the same type of material. For example, in the first category of materials, 0 and 1 represent impregnation varnish; 2 represents coating varnish. In the second category of materials, 0, 1, and 2 represent cotton fiber coated cloth; 4 and 5 represent glass fiber coated cloth; 6 represents semiconductor coated cloth and adhesive tape; 7 represents coated tube; 8 represents thin film; and 9 represents thin film products.
The third digit indicates the insulation and heat resistance class of the material. For example, 1 - Class A; 2 - Class E; 3 - Class B; 4 - Class F; 5 - Class H; 6 - Class C.
The last digit indicates the material serial number, which indicates the difference in formulation, composition and performance between similar insulating materials. For example, 1032 and 1031 are both Class B insulating impregnating varnishes, but 1032 is melamine alkyd varnish and 1031 is butylphenol alkyd varnish.
