Hoffman Fan Motor Speed Controls EC

The Hoffman Fan Motor Speed Controls EC has the job of controlling the speed of EC motor using the motor’s built-in tachometer signal. Control can be locally using the LED display and the buttons on the control. It can also be done remotely via the Modbus RTU interface. Control of the speed can be manual (open loop) or automatic (closed loop).

In manual mode, a speed index (0-100) is used to set the control signal to the motor. Both the speed index and the motor rpm are visible on the LED display and over the Modbus. In automatic mode, the motor rpm is set directly and the control uses a PI feedback algorithm to drive the motor rpm. It is then sensed by the tachometer signal to the set value.

The control has two outputs that may be used to control the motor. One is a 0-10VDC output, and the other is a PWM output (0-17 volt, 80 Hz). Each output can supply up to 10 mA to drive the motor. A “GO” signal is also provided for motors that require this.