What's the difference between a brushless motor and a brushed motor?

brushed motor

Construction Differences

Brushes inside electric motors are used to deliver current to the motor windings through commutator contacts. Brushless motors have none of these current-carrying commutators. The field inside a brushless motor is switched via an amplifier triggered by a commutating encoder, such as an optical encoder.

Windings are on the rotor (rotating part of motor) for brush motors and on the stator (stationary part of motor) for brushless motors.

By positioning the windings on the outside stationary portion of the electric motor, the need for brushes can be eliminated.

brushed motor structure and working principle

Brushed motor Advantages:

Simplified wiring: Brush motors can be wired directly to DC power and control can be a simple as a switch;

Low cost.

Brushed Motor Disadvantages:

Less efficient;

Electrically noisy: The switching action of the commutators constantly creating and breaking inductive circuits creates a great deal of electrical and electromagnetic noise;

Lifespan: As they are in perpetual physical contact with the shaft, brushes and commutators wear out.


Brushless Motor Advantages:

Long lifespan: No brushes to wear out;
Low maintenance: No brushes to replace;
High efficiency.

Brushless Motor Disadvantages:

Higher initial cost compairing to brushed motor.
brushless motor structure and working principle
Brushless Motor vs Brush Motor Efficiency:

Brushless motors are typically 85-90% efficient whereas brushed DC motors are around 75-80% efficient.

This difference in efficiency means that more of the total power used by the motor is being turned into rotational force and less is being lost as heat.