What is the difference between brushed DC and brushless DC motors?

What factors need to be considered when choosing a motor

The main difference between brushed and brushless motors is the service life. The service life of the brush motor is shorter and is limited by the wear of the brush, while the ball bearing wear of the brushless motor is much greater.

For many applications, the shorter service life of the brushless motor is not a problem, because it can be compensated for at a lower cost. The service life may vary from 100 to 10,000 hours, depending on factors such as the current load, speed, vibration, and reversal frequency. The average is about 2,000 hours. On the other hand, brushless motors can provide tens of thousands of hours of service life.

Another consideration is speed. Generally, the maximum speed of a brushed motor is 20,000 RPM, but within this range, electrical and mechanical wear will increase sharply, thereby greatly shortening the service life. In fact, the running speed of a brush motor is usually less than 10,000 RPM. Brushless motors of similar size and magnetic design can run at higher speeds, in some cases up to 100,000 RPM. These are ideal motors for applications where speed is critical.

But these are generalizations. You must check the data sheet of each motor for precise information about the speed and torque functions.

Environmental conditions are another factor. If you are concerned about electromagnetic interference, the brush motor may not be suitable due to a phenomenon called brush fire. In an explosive gas environment, brush sparks are a serious problem. Brushes made of graphite require atmospheric moisture and oxygen to work properly, and generate dust that may contaminate clean rooms, high vacuum, or optical equipment.

For these reasons, most motors under special environmental conditions are brushless. There are no physical brush residues or spark-related emissions. Brushless motors are not inherently explosion-proof, but they can be easily made with special modifications. They can be sterilized and operated in ultra-high vacuum applications that require preheating, making them ideal for medical applications. Brushless motors can also withstand high levels of vibration and high temperatures.

No other kind of motor is as simple as a brushed DC motor. It only needs to apply a voltage to make the motor rotate. Brushless motors require electronic controllers and additional cables, adding complexity and cost. However, this advantage is offset in applications that require higher levels of control. In these applications, both brushed and brushless motors require a controller to control motor speed, shaft position, or torque feedback.

Therefore, whether it is brushed or brushless, in the end, you must choose according to the speed, service life, installation complexity, and environmental requirements of the specific application.