Insulation class determines what temperature the motor winding can withstand without destruction. This is one of the key parameters when selecting and when winding rewind. Let's look at classes B, F and H.
What do the classes mean?
| Class | Temperature limit | Application |
|---|---|---|
| B | 130 °C | Obsolete and household motors |
| F | 155 °C | Modern industry standard |
| H | 180 °C | Heavy conditions, high loads |
The specified temperature is the maximum permissible winding temperature at which the insulation serves the design period.
How the class affects the resource
The rule is simple: exceeding the permissible temperature for every 8–10 °C reduces the service life of the insulation by approximately half. Therefore, a motor with class F insulation has a larger heating margin than class B and lasts longer under the same conditions.
What to choose when rewinding
When rewinding, it makes sense to use materials not lower, and often higher than the original class. For example, replacing class B insulation with F during rewinding increases reliability and heating margin without changing dimensions. For engines operating in the heat of Tashkent or with frequent starts, class F or H is a reasonable choice.
- The standard choice is class F.
- Heavy conditions, hot shops - class H.
- Class B is rarely used today.
Are you planning rewinding and don’t know which insulation class to choose? Elektromotors engineers in Tashkent will select materials for operating conditions - leave a request.