How Does the 250W 12-48VDC 15A Variable-speed Motor Controller (FS-03-48V) Regulate Motor Speed?

This speed controller operates by using a potentiometer (sliding resistor) to output a 0–5V analog voltage signal, which corresponds to a speed range of 0 to maximum RPM, thereby setting the target speed. Currently, this controller is compatible with all our DC brushed motors.

Basic Speed Control Logic: Voltage Determines Speed

The rotational speed of a DC brushed motor follows the core formula:

n = (U – I×R) / (K×φ)

Where:

• n = motor speed
• U = voltage applied to the motor terminals
• I = motor current, R = motor winding resistance
• K = motor constant, φ = magnetic flux (typically constant in brushed motors, determined by permanent magnets or field windings)

When the magnetic flux φ remains constant (as in most permanent magnet brushed motors), the motor speed n is approximately proportional to the effective voltage (U – I×R) across the motor. Therefore, the core principle of the speed controller is to adjust the motor speed by varying the effective voltage applied to the motor.

Updated on: 30/10/2025