Brushed Motors vs. Brushless Motors

Electric motors are a lynchpin of modern automation, delivering efficient performance across diverse industrial applications. These tools convert electrical energy into mechanical energy, generating substantial motion and torque to drive a load. Machine builders use various motor types to achieve different functions and efficiencies—and one of the most common distinctions is brushed vs. brushless motors.

Brushed DC motors were first invented in the 19th century. These motors rely on soft contacts called “brushes” to carry electric current. With time and innovation, new “brushless” DC motors were developed—followed by AC servo motors, which also feature a brushless design. But why would machine builders favor brushless motors over their forebears? Let’s explore the benefits and drawbacks of each to find out.

What are Brushed Motors?

Brushed motors are composed of four primary parts: the armature, commutator, permanent magnets (or stator), and brushes. When connected to a power source, the opposite polarities of the magnets create a magnetic field, which in turn creates motion as current is passed through the armature coils. In this system, the brushes are used to connect the rotating armature coils with the external power supply. As more current is sent to the armature coils, the strength of the electromagnetic field increases.

The “brushes” used in brushed motors are typically made from carbon or graphite. They can also be outfitted with dispersed copper to improve their conductivity. Over time, these brushes wear down and must be replaced through regular maintenance.

Advantages and Disadvantages of Brushed Motors

There’s a good reason why we’ve been using brushed motors for almost 200 years: they’re simple, inexpensive, and offer dependable control for motor speeds. Their low initial costs and reliability make brushed DC motors well suited for a range of applications, especially when the lifespan of the motor is not expected to last long.

The main challenge with brushed motors is an inherent weakness in their design: they rely on short-lived brushes and a spring mechanism to function. Of course, these components naturally wear down and break with continued use. That means an increased need for maintenance to prevent system failure, unplanned downtime, and other issues. A brushed motor’s commutator must also be cleaned and replaced with use. High maintenance and short lifespan across high-intensity applications are the key downsides of brushed motors. In fact, these weaknesses may have inspired the creation of brushless motors in the early 1960s.

Another side effect is that as brushes wear, they create carbon dust which can be dispersed in the operating environment. This conductive dust can contaminate external nearby processes.

DC to AC Elevator Modernization

What are Brushless Motors?

Brushless DC motors use a combination of permanent magnets and electromagnets, along with a motor controller to convert DC to AC. This simplified design eliminates the need to transfer power from outside the motor to the rotor within. Brushless DC motors use sensors to detect the exact position of the rotor—which allows for more precise control to regulate speeds, improve torque, and conserve power.

The latest models of brushless motors include AC synchronous servo motors, which are ideal for today’s demanding industrial applications. These devices use servo controllers and feedback devices to help coordinate and adjust the motor action, which helps optimize torque, velocity, and overall performance.

Advantages and Disadvantages of Brushless Motors

One of the primary drawbacks of brushless motors vs. brushed motors is their upfront cost. Brushless motors and their related amplifiers utilize more complex parts and processing power to function, which drives up their price by comparison. However, this cost premium is offset somewhat by their reduced need for frequent maintenance and part replacement.

Brushless motors offer better shaft performance overall compared to brushed motors, primarily because they use electronic controls or sensors to communicate with the rest of the system. A brushless motor can detect and use the exact amount of current it needs to drive a load, creating greater efficiency and improving the lifespan of the motor. Brushless motors are also powerful for their size, meaning that even a compact motor can offer plenty of power.

Brushless servo motors offer unique advantages as well. These motors are lightweight and produce substantial torque compared to induction motors of similar size. They balance great performance and efficiency with a long lifespan—and can be configured with various feedback and brake options for increased versatility.

KEB: Your Partner in Industrial Automation

As a leader in automation and control, KEB offers a wide range of high-performance motors to suit your unique application. Our DL3 servo motors come with low and medium inertia models. They can be coated with special epoxy to simplify washdown for applications involving moisture and chemical exposure. We also offer a C6 I/O EtherCAT stepper drive, which can actuate a stepper or brushless DC motor with an incremental encoder.

If you have any questions about different motor types and choosing the right one for your application, please contact an application engineer today. We’re here to help!