EC fans are powered by brushless DC motors. These motors are also known as Electronically Commutated motors or EC motors. A typical EC motor has a rotor of permanent magnets which rotates in (or around) the stator. The built-in fan speed controller generates electric current in the stator windings. This electric current generates a rotating magnetic field. The permanent magnets follow this rotating magnetic field and the motor runs.
The control electronics (fan speed controller) are always integrated in the EC motor since this motor type requires a coordination between rotor position and motor currents. Without this coordination, it would not be possible to start up the motor. This integrated fan speed controller converts the mains (AC voltage) into a DC voltage that is required to control the motor.
Next to the mains (230 VAC power supply), it requires a control signal that specifies the requested fan speed. This control signal can be digital (Modbus RTU communication) or analogue (typical 0-10 Volt). The control signal can be generated manually via a control switch (in steps) or via a potentiometer. It can also be generated by an HVAC sensor or an HVAC controller. In that case, demand based fan speed control is possible.
The main advantages of EC motors are:
The difference in energy consumption between an AC and an EC motors is clearly visiblee at reducd speed. At nominal speed, energy savings around 10 % can be achieved.
However, the permanent magnets and the integrated electronics make this type of motor rather expensive. The higher purchase price is compensated by its lower energy consumption.
Since EC fans have a built-in fan speed controller, they just require a control signal that defines the requested fan speed. The type of this control signal depends on the EC motor type. Typically this is an analogue 0-10 V signal but more and more EC fans are available with Modbus RTU communication. The control signal can be created manually or automatically.
If you want to control fan speed manually, the control signal can be generated via:
If you want to control fan speed automatically or demand based, the control signal can be generated via: