EC Motor: Closed Loop Speed Control


A Control Circuitry can be added to the Driver Circuitry.
Hall sensors (or an additional optical encoder) are used to measure the actual speed of the rotor. This signal is the actual value input for a Control Circuitry, usually based on PI control algorithm.

ec motor


The voltage level to the motor is adjusted by implementing an additional feature inside the driver circuitry:
Pulse Wave Modulation PWM.

The average voltage to the 3 windings can be varied by switching supply voltage ON/OFF.
The switching frequency is very high (10 kHz or higher).

ec motor   ec motor

ec motor

Speed can be held on a constant level, independent from load torque.
However, the Performance Curve PC can’t be higher than that of open loop operation.

That must be considered when designing the PC for closed loop operation.

Motor manufacturing tolerance should be considered too
(no load speed speciefied +-10% usually).