As all we know that it will have some power loss when the DC motor is running with load. These loss will be changed to heat energy, which will causes temperature rising. The value of the dc motor temperature which higher than the surroundings is called temperature rise. Once temperature is increased, the heat-dissipating is needed. The higher the temperature, the faster the heat.

When the bldc motor heat emitted per minute is equal to the heat-dissipating, and then the motor temperature will not increase, just keep a stable temperature. That means the motor is in balanced state of heating and cooling.

Motor power must be limited within a range, because the size of the motor is fixed, and all of its cooling area is fixed too. This determines the motor can withstand the temperature within a range, otherwise the brushless motor will be burned.