What is the difference between brushed DC and brushless DC motors? What to consider when choosing a motor

The main difference between brushed and brushless motors is the longevity. Brush motors have a shorter lifespan and are limited by brush wear, whereas brushless motors have much more ball bearing wear.

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

Another consideration is speed. Typically, brushed motors have a maximum speed of 20,000 RPM, but within this range electrical and mechanical wear increases dramatically, drastically reducing service life. In practice, brushed motors typically run below 10,000 RPM. Brushless motors of similar size and magnetic design can operate at higher speeds, up to 100,000 RPM in some cases. These are ideal motors for applications where speed is critical.

But these are generalizations. You must check each motor's datasheet for precise information on speed and torque capabilities.

Environmental conditions are another factor. If electromagnetic interference is a concern, a brushed motor may not be suitable due to a phenomenon called brush fire. In explosive gas atmospheres, brush sparks are a serious problem. Brushes made from graphite require atmospheric moisture and oxygen to function properly and create dust that can contaminate cleanrooms, high vacuums or optical equipment.

For these reasons, most motors for special environmental conditions are brushless. No physical brush residue or spark-related emissions. Brushless motors are not inherently explosion proof, but can be easily made with special modifications. They can be sterilized and operate 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 motor is as simple as a brushed DC motor, just applying a voltage to make the motor turn. Brushless motors require electronic controllers and extra cables, adding complexity and cost. However, this advantage is negated in applications that require a higher level of control, where both brushed and brushless motors require a controller to control motor speed, shaft position or torque feedback.

So, whether brushed or brushless, ultimately, you have to choose based on the speed, longevity, installation complexity and environmental requirements of your specific application.