Why is the border line of the continuous operation range of EC motors curved?
Border continuous operation range
The border of the continuous operation range is given by
- the maximum winding temperature of 125°C
- and the ability of the motor to dissipate the produced heat.
The winding of EC motors is heated up
- directly by Joule power losses (electrical resistance)
- indirectly by the speed dependent iron power losses in the magnetic return (hysteresis and eddy current losses).
The eddy current losses increase with the square of the speed. At high speeds considerable heat is produced simply by the rotating magnet. Therefore, only a small amount of current can flow without overheating the motor.
At higher speeds a smaller output torque is available.