What is a geared brushless DC motor?

Recent years have seen the development of a steady stream of new high-performance electric motors.

In particular, brushless DC motors have been developed to overcome the shortcomings of conventional brushed DC motors.

Brushless DC motors are smaller, lighter, quieter, and have a longer operating life than their brushed counterparts, also offering superb performance in terms of efficiency and controllability. However, the technical difficulties of designing small motors to operate at low speeds of a few hundred rpm make a gearhead essential in such applications. With the addition of a gearhead, the motor is able to deliver high torque and low speed while still maintaining all of the benefits of a brushless DC motor.

A geared brushless DC motor is a motor with a built-in gear mechanism (such as a multi-stage or planetary gears). The gears are connected to the motor drive shaft.

Gears housed in a geared brushless DC motor

You can see in this image how the gears are housed in the motor case (the orange and yellow parts are the gears, with the encased motor on the right).

The gears engage with one another to step down the speed of the brushless DC motor while also increasing the output torque (angular moment).

Brushless DC motors are typically operated at speeds of 2,000 to 3,000 rpm where they achieve excellent efficiency. If the motor is combined with a gearbox that has a 20:1 gear ratio, for example, this speed can be stepped down to 100 to 150 rpm with an accompanying 20-fold increase in torque.

Step-down gearing is usually assembled and attached to the motor in an encased gearbox. Combining the motor and gearbox in a single housing can reduce the external dimensions of geared brushless DC motors, which helps make effective use of space in the machinery in which they are installed.

The design of a geared brushless DC motor is determined by factors that include its required output speed and torque and the space available for installation. Fortunately, this equipment design is made easier by the wide range of choices that brushless DC motors offer for these basic performance parameters.

The following reasons explain why geared brushless DC motors are so widely used.