EC Motors: Basic Configuration

EC motors have their windings in the stator, not in the rotor like brushed DC. The mechanical commutator/brush system is replaced by an electronic commutator – the EC driver motor

The driver circuitry switches the DC supply voltage onto motor windings. Most EC motors have 3 windings in star connection.

The star point is connected internally, with only 3 wires to outside.

Applying PWM (Pulse Width Modulation) the driver circuitry can change the average voltage to the motor to control the speed.

Permanent magnets are located in the rotor.

3 Hall sensors, embedded in the stator, measure the angular position of the rotor. Whenever the rotor magnetic poles pass near the Hall sensors, they release a signal, indicating the N or S pole is passing.

These signals enable the driver circuitry to find the optimal switching time for the 3 windings.

ec motor  


Sensorless version

EC motors can also be commutated by monitoring the back EMF signals instead using Hall sensor signals.

The motor has to be started in open loop. Then the control is shifted to the back EMF sensing. There is restriction to applications with rather constant torque and no dynamic requirements, for instance fan or pump drives.