The power losses in electric machines are converted to heat. The generated heat tends to raise the internal temperature of the machine. To keep the temperature inside the machine below specified limits, the generated heat must be removed from the machine.
- The most common method of machine cooling is forced-air cooling using a fan mounted on the rotor shaft.
- In very large machines, or when, due to the special operating conditions, a totally enclosed machine has to be used, a liquid coolant may be circulated through the potentially hot spots of the machine to remove the heat from the machine.