High temperature motors

For which temperatures

The standard operating temperature for each motor is equal to 40°C. A power downgrading, also depending on the sea level, is executed for motors working at temperatures starting form 45°C up to 60°C . (see the attached table). If the temperature increases, it will be necessary to adopt particular solutions while manufacturing the motor to make it able to work at surrounding temperatures up to 180°C.

Which special treatments

The following measures are taken to guarantee the correct functioning of the electrical motors at high temperatures :
-Electrical winding: the copper wire is designed to resist to class F or H temperatures . So, every application needs its suitable wire. Every wire is then wrapped, in quarries, by a pure Nomex coverage for H class and by a Mylar one for F class. 
-cooling fan: the common plastic one is substituted by a fan made with special material, able to operate at high temperatures. 
- Corteco seal: usually made with NBR, is replaced with a VITON special seal.
-Terminal: is manufactured, depending on temperature, with resistant resins.

Overtemperature class

The overtemperature class is a value to be add to the surrounding temperature in order to determinate the final work temperature. It’s a value generally provided by the motor constructor. The allowed temperatures in the windings for each insulation class, in according with the surrounding temperatures , are:
Class B :80°K
Class F:105°K
Class H: 125°K

What does insulation class B, F, H mean

The insulation class of an electric motor indicates the maximum reachable temperature, in according with surrounding temperature, by its own windings: a high value of allowed overtemperature highlights an use of high quality insulating material in the machine construction, to be used in particularly difficult situations. The following are the insulation classes, with their maximum temperatures in the windings (including a security factor):
Class B Tmax=130°C 
Class F Tmax=155°C
Class H Tmax=180°C
Another important value is the complete lettering F/B or H/F. This means, taking the F/B as example, that the motor is wrapped in F class but its temperature doesn’t move from that of B class (cool motor). This lettering is very useful to determinate the windings real temperature.