Q9Electrical Machine Design
Question
Q.9. What is the maximum temperature limit for Class-B insulation?
Answer
Class-B insulation has a maximum permissible operating temperature of 130°C.
According to standard insulation temperature classification (IEC/IS), Class-B insulation (typically composed of mica, glass fiber, or asbestos with suitable bonding materials) has a maximum permissible operating temperature limit of 130°C. This is one of several standard insulation classes (Y-90°C, A-105°C, E-120°C, B-130°C, F-155°C, H-180°C), each specifying the maximum hot-spot temperature the insulation can withstand continuously without unacceptable degradation of its service life, and this limit is a key input constraint in determining the permissible temperature rise (and hence current loading) of a machine during electrical machine design.