Brushless vs Brushed Motor Technology Explained

brushless vs brushed motor technology

Brushless motors have become increasingly popular in the professional tool industry for use in cordless tools. In fact, even the least expensive brands produce core tools that use brushless motors. While it may not seem like a significant change, there are actually major differences between brushless vs brushed motor technology. Given these differences, we felt it important to explain the benefits of brushless motors so you can make an informed decision about which tools to buy and use.

How Brushed DC Motors Works

Parts of a Brushless Motor

A brushed DC motor consists of a stator (the stationary part of the motor) and an armature (the moving or rotating part of the motor). Typically, the stator consists of a core made of stacked laminated steel that surrounds the rotor and armature (copper windings around the core). On smaller motors, the stator could also simply be a set of permanent magnets. The armature is a series of coils that become electromagnets when you apply power.

electric brushed armature

The stator and armature windings in the brushed motor need to connect to a DC power source. But how? They do this through a pair of carbon brushes and a commutator—a rotating cylinder that transfers electrical power to the coils of the armature and the electromagnet of the stator. The commutator rings are fixed to the armature coil in two (2-pole configuration), four (4-pole configuration), or more pieces. They spin with the armature.

Copper segments mounted on the commutator connect to the stator and armature windings. As the commutator rotates with the rotor, it contacts the carbon brushes and the commutator switches the current in the windings. The rapidly changing polarity causes the rotor to continue turning within the stator.

The direction of the rotor’s rotation can be reversed by reversing the polarity of the DC power source. You can vary the speed of the motor by adjusting the voltage of the DC power source.

Overall, a brushed DC motor relies on physical contact between the brushes and the commutator to transfer electrical power to the rotor and produce motion.

The Movement of the Armature

Once you power the armature, each charged coil pulls toward its oppositely charged permanent magnet or electromagnet. As the commutator ring above it also spins, it moves from a connection with one carbon brush to the next. When it reaches the next brush, it receives a polarity reversal. Now it wants to move toward the other permanent magnet while being simultaneously repulsed by the like charge.

As the cycle repeated, the motor spins. The presence of multiple coils and contact points on the commutator ensures a smooth rotational motion.

DC brushed motor

Imagine a brushed motor like an indecisive person. This person constantly changes his mind between two conflicting desires – a tasty but unhealthy apple fritter and a healthier smoothie. It’s like he’s caught in a loop, chasing one and then the other, but never able to make a decision. It’s like he has ADHD and can’t focus on just one thing. Even when he tries to choose the smoothie, the allure of the apple fritter still pulls him back. The two parts are at odds with each other, each passionately but indecisively chasing after their respective object of desire at nearly the same time.

How Brushless Motor Technology Differs vs Brushed

In a brushless motor, the traditional commutator and brushes are replaced with an electronic controller. The permanent magnets, which act as the rotor, are now located on the inside of the motor and rotate around the stator. The stator is made up of electromagnetic coils that are fixed on the outside of the motor. The electronic controller powers each coil according to the necessary charge to attract the permanent magnet.

The electronic controller in a brushless motor not only moves the charge around, but it can also provide a like charge to oppose the permanent magnet located on the rotor. Since like charges oppose each other, this creates a push on the permanent magnet, causing the rotor to move. The rotor is therefore moved by both a pull and a push.

brushless motor disassembled

In this scenario, the permanent magnets are like my running partner and me, and we have made our decisions about what we want. I have chosen the apple fritter, while my partner wants the fruit smoothie. We are no longer indecisive or changing our minds.

Milwaukee brushless motor

The electronic controller keeps dangling our preferred breakfasts in front of us so that we’re always moving forward. It also pushes us from behind using what we don’t want.

The Cost of Brushed vs Brushless DC Motors

Copper costs remain the same in both brushless and brushed DC motors—and sometimes brushless motors can use more material. Still, brushed motors generally cost less than comparable brushless motors. Brushed motors simply have fewer components and less complexity. This makes them easier and less expensive to manufacture.

Brushless motors, on the other hand, feature that electronic controller to operate. The addition of electronics—basically a small computer—adds to the overall cost. Brushless motors also tend to be more efficient and have longer lifespans, which may justify the higher upfront cost for some applications.

Makita brushless motor opened

Brushed vs Brushless Motor Efficiency

Brushless motors offer several advantages in efficiency over brushed motors. The design removes both brushes and the commutator. Without brushes that require physical contact with the commutator, you eliminate wasted power and speed losses through friction and heat. You also reduce wear and tear on the rotor.

Bicycle Brake Pad Brushed vs Brushless Motors

Running a brushed motor simulates riding your bike with the brake calipers always slightly touching the rim of your wheel. That small amount of friction still takes its toll eventually on your efficiency and speed. In fact, to maintain the same speed, it requires more energy from your legs. You also produce heat along the rim of the tire from the friction. As a result brushless motors simply run cooler than brushed motors. They also convert electricity into power more efficiently.

Ever notice the spark inside a brushed tool when you pull the trigger? That’s actually small bits of metal coming off the carbon brushes. As they wear down over time, they eventually fail. To keep a brushless tool operating,you eventually need to replace the brushes. Brushless motors don’t require that type of routine maintenance.

Brushless motors require an electronic controller, but that leaves the rotor/stator combination smaller in size. The result is smaller, lighter, and more compact tools. We see this with products like the Milwaukee M12 brushless pruning shears which have a super-compact inline design and plenty of power.

Milwaukee M12 Brushless Pruning Shears

Brushed vs Brushless Motor Torque

When you compare brushless vs brushed motors, it’s easy to assume the former provides more torque. In truth, brushed or brushless motor design doesn’t in itself indicate better or worse torque. We remember back to the first Milwaukee M18 FUEL (brushless) hammer drill. It actually had less real-world torque than their top-of-the-line brushed model that preceded it.

Manufacturers eventually realized a key point: the electronics used in brushless motors can increase the power supplied to those motors as needed. Instead of a “dumb” motor that increases speed with supplied voltage, brushless motors had some inbuilt intelligence that could make up gains lost due to encountering high torque applications.

Brushless motors, like those used in electric lawn mowers and battery-powered weedeaters can sense when they begin to slow down under load. As long as the battery and motor are operating within their temperature limits, the electronics of a brushless motor can request and receive additional current from the battery. This results in stronger, faster tools. You can see examples of this in the performance of Milwaukee’s RedLink Plus, Makita’s LXT Advantage, and DeWalt’s Perform and Protect line of products.

These technologies seamlessly blend the tool’s motor, battery, and electronics into a cohesive system to achieve the best possible performance and runtime.

Sensor-free Brushless Motor Technology

Hall sensors are a type of electronic sensor used to measure the presence and strength of a magnetic field. Named after their inventor, Edwin Herbert Hall, these sensors appear help many brushless motors detect the position of the rotor. By detecting the position of the rotor, the Hall sensor allows the motor controller to determine the proper timing and sequence for applying current to the windings of the motor.

Sensor-free brushless motors forgo Hall sensors and use an algorithm to estimate the position of the rotor based on the current supplied to the windings and the voltage of the motor.

Sensor-free brushless motors have some advantages over traditional brushless motors. First, they cost less to manufacture and involve less parts. Secondly, they give you more space. That means you can fit more “motor” in the same package. They can also increase reliability since they do not have the potential for sensor failure. We’re seeing more and more sensor-free brushless motors hit the market.

The Final Verdict

The various benefits of brushless motors, including increased efficiency, power, and speed, also contributes to a longer lifespan for the motor (and consequently, the tool). While the warranties for brushed and brushless motors and tools may be similar within a particular brand, it is common for brushless models to have a longer lifespan, potentially lasting for several years beyond the warranty period.

This makes brushless motors a more cost-effective option in the long run. The increased durability and longevity of brushless motors is a key factor that contributes to their growing popularity in a variety of applications.

Related articles

Altoz Zero-Turn Mowers – Which One Do You Need?

Altoz Has a Fleet of Residential and Commercial ZTM Mowers Having reviewed the Altoz XC 610 Zi zero-turn mower and the Altoz TRX 660i zero-turn mower, we’re familiar with the brand. Altoz continues to announce additional models that expand its line of zero-turn mowers. With a variety of models, engines, deck widths, drive systems, features, […]

Mean Green Opens New Hamilton Ohio Facility

Generac Power Systems’ brand, Mean Green, has announced the opening of a new 100,000-square-foot facility in Hamilton, Ohio. The new space should help the company meet the increasing demand for electric-powered zero-turn mowers. The company previously produced four different commercial electric mowers and accessories at its Ross, Ohio location—about 10 miles away. The expansion will […]

Greenworks New Tools and Gear for 2023

Greenworks Widens Its Gaze and Enters Home Technology Space at CES 2023 You probably recognize Greenworks for its electric lawn care products or cordless power tool lineup, but the brand has a few new products that may seem a little out of the blue at first. We’re looking at the new Greenworks tools and gear […]

Subscribe
Notify of
guest

0 Comments
Inline Feedbacks
View all comments
0
Would love your thoughts, please comment.x