DC motors are used in a variety of different applications. Any function that requires be the smooth and seamless operation of a motor requires DC motor drives that help to maintain speed. DC motor drives also aid in braking and reversing in cars and motorcycles.

Sometimes referred to as variable speed drives, DC motor drives are amplifiers that sit between a control unit and a DC motor and convert the incoming signals into currents and voltages. This is necessary to supply the motor with a signal that it can interpret.

DC motor drives can be used inside DC motors to regulate the speed of rotation, torque, power output, and direction of the motor. Since DC motors are capable of producing a high amount of horsepower and large torques, and the motor drives play a key role in these abilities.

Types of DC Motors Drives

There are a few different kinds of DC drives. The type that you use depends on the application of the motor. The main types of DC motors and DC motor drives include brushed, brushless, linear, voice coil, and servo.

Let’s take a look at each of these in more detail.


  • Brushed motor – this type of motor uses rotating coils that move around an iron core. They commentate through physical contact between several brushes.
  • Brushless motor – in a brushless motor, there are no graphite brushes. This type of motor commutates electronically, without any physical contact being required.
  • Linear – this type of motor uses typical rotary motor components that are organized linearly. It generates a high level of force in one direction and is capable of powerful acceleration.
  • Voice coil – a voice coil motor has a magnetic coil that gets placed in a magnetic field. A current is pumped through the coil, causing it to rotate.
  • Servo – a servo motor can be either brushed or brushless. It has an internal sensor that helps to keep the motor functioning properly. If the servo motor is brushless, the commutation occurs with three distinct phases and the sensor helps to control these phases.

Controlling the Speed of DC Motor Drives

The speed of a DC motor drive can be controlled via a selection of methods, including armature voltage control, armature resistance control, and field flux control.

  • Armature voltage control – this particular method controls the speed of the motor below the rated speed
  • Field flux control – this method regulates above the rated value. Usually, the control level is around twice the rated speed but anywhere up to six times the rated speed.
  • Armature resistance control – this method uses varying speed controls based on the application, the duration of operation, and the total running time.

Specifications for DC Motor Drives

There is a variety of specifications that need to be considered when choosing a DC motor drive, including:

  • Power supply
  • Voltage supply
  • Current during operation
  • AC input frequency
  • Additional features, such as programmability or auto stop-start

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