The permissible temperature rise of electrical machines is determined by the type of _____.

Temperature rises in electrical Machines are due to power losses occurring in various parts of the machines.

The various power losses occurring are rotational loss, friction and windage loss, and electrical and magnetic losses.

The permissible temperature rise of electrical machines is determined by the type of insulation materials used for winding.​

Properties of insulating materials for electrical machine

A perfect insulating material ought to possess the subsequent properties:

• High dielectric strength.
• It should withstand high temperatures.
• Good thermal conductivity.
• It should not undergo thermal oxidation.
• It should withstand vibration, abrasion, and bending.
• Not to absorb moisture.