For several years now, we’ve been seeing brushless motors begin to dominate the professional tool industry’s drive in cordless tools. That’s great, but what’s the big deal? As long as I can still drive that timber screw, does it really matter? Well, yes it does. Significant differences and implications exist when dealing with brushed vs brushless motors.
A drill motor is designed to convert electrical power into mechanical motion. The market is filled with a wide variety of motors that can handle different applications and varying power requirements. The two most common types of motors include brushless and brushed motors. Although they are based on the same physical principles, their structure, performance and control differ significantly.
What is the Difference Between Brushed and Brushless DC Motors?
A brushed DC motor uses a configuration of wound wire coils, the armature, acting as a two-pole electromagnet. The current’s directionality is reversed twice per cycle by the commutator, a mechanical rotary switch. This facilitates flow of the current through the armature; thus, the electromagnet’s poles pull and push against the permanent magnets along the outside of the motor. The commutator then reverses the polarity of the armature’s electromagnet as its poles cross the permanent magnets’ poles.
A brushless motor, by contrast, utilizes a permanent magnet as its external rotor. In addition, it uses three phases of driving coils and a specialized sensor that tracks rotor position. As the sensor tracks the rotor position, it sends out reference signals to the controller. The controller, in turn, activates the coils in a structured way – one phase after the other.
What is a brushed motor?
A brushed DC motor uses wound wire coils, called the armature, which act as a two-pole electromagnet. Twice per cycle, the current’s directionality is reversed by the commutator, which is a mechanical rotary switch. The electromagnet’s poles pull and push against the permanent magnets along the outside of the motor. The commutator then reverses the polarity of the armature’s electromagnet as its poles cross the permanent magnets’ poles, to form a direct current.
Brushed motors were the first commercially important motors, and have been used for well over 100 years to operate motors in commercial and industrial applications. They are the most basic and have been in use since the late-1800s.
Brushed motors can be varied in speed by changing the operating voltage or the strength of the magnetic field within them.
How Brushed Motors Work
In a typical electric motor, there are permanent magnets (stator) on the outside, and a spinning armature (rotor) on the inside. The rotor contains an electromagnet. When electricity passes through the electromagnet, it creates a magnetic field inside the rotor that attracts and repels permanent magnets in the stator.
However, to make the motor spin 360 degrees, it’s necessary to change the polarity of the electromagnet, and a pair of brushes helps do that.
Motor brushes aren’t brushes at all, but small blocks of carbon connected to a compression spring. The brushes press against spinning electrodes attached to the rotor. As the electromagnet spins, the brushes change the magnetic polarity.
Brushed motors are reliable, relatively efficient and inexpensive to manufacture, but they have distinct limitations.
What Does Brushless Mean
In a brushless motor, you lose the commutator and brushes while gaining an electronic controller. Now the permanent magnets act as the rotor and rotate around on the inside while the stator is made up of the fixed electromagnetic coils now on the outside. The controller powers each coil according to what charge it needs to attract the permanent magnet.
In addition to moving the charge around electronically, the controller can also provide a like charge to oppose the permanent magnet. Since like charges oppose each other, this pushes the permanent magnet. Now the rotor is moving thanks to a pull and a push.
The permanent magnets are moving in this case, so now they are my running partner and me. We aren’t changing our minds about what we want anymore. Instead, we know that I want the Boston creme doughnut and my partner wants the smoothie.
The electronic controller keeps our respective breakfast delights moving in front of us and we’re always chasing the same thing. The controller also puts what we don’t want right behind to offer a push.
Brushed vs. Brushless Motors: Advantages of a Brushless Motor
All cordless drills convert electricity into power by using the attracting and repelling actions of magnets to get the shaft spinning. Brushed motors require small metal brushes to work with the magnets to keep the shaft spinning. Brushless models have an electronic circuit board and a sensor to do the same thing. That has several advantages when it comes to performance, reliability, and durability. Brushless motors are:
Because there are no brushes rubbing against anything, no energy is lost due to friction. That means brushless motors are more energy-efficient than brushed drills and can run on batteries for up to 50 percent longer. “That energy efficiency translates into more powerful drills because there’s no mechanical limitations posed by brushes,” says John Banta, a senior test project leader at CR.
A drill with a brushless motor adjusts its speed, torque, and power supply to match the task at hand. It’ll sense if you’re driving screws into a light material like drywall or a dense material like mahogany, and use only enough power to accomplish the job. (This battery power conservation also contributes to the brushless motor’s efficiency.) A brushed motor will use the same amount of power no matter what resistance it’s up against.
Capable of packing more power, torque, and speed
Without brushes to cause friction and slow things down, brushless drills pack more power and torque. They can reach higher speeds, too. “You can expect a 15 to 35 percent increase in performance compared with a brushed motor drill,” says Banta.
Easier to maintain
A brushed drill requires new brushes after every 50 to 60 hours of use, but brushless models don’t have any brushes that need replacement.
Smaller and lighter
Brushless motors are also smaller than brushed motors, which brings down the overall size of the tool. Lauren Chell, a product manager at Dewalt, cites an example of a brushless model that’s 25 percent more compact than the brushed version the company makes. “For a compact drill, you could see a reduction of 1 pound and over 1 inch in length,” Chell says.
What does that mean when using a drill? Banta says you can get into tighter spaces with the same or better power.
No friction in a brushless drill means less wear and tear, and less heat. “Excessive heat is the enemy of both the motor and the battery,” says Wayne Hart, communications manager at Makita. “And a brushless motor runs up to 50 percent cooler than a brushed motor.”
With a brushless drill, any heat that does develop dissipates faster because the winding mechanism that creates heat is on the casing of the drill rather than in the interior. Because of this, brushless drills don’t need air vents on its casing for cooling, so they’re better protected from dirt and debris than brushed versions.
Best Brushless Drills of 2021:
Milwaukee tools are everywhere these days, and for a good reason: they’re powerful and reliable. Although this brushless drill is 18-volt compared to 20-volt competitors, it produces a robust 57Nm of torque. With speeds up to 1800rpm, this tool can handle heavy-duty drilling.
One of the prime features of Milwaukee cordless products is their RedLithium batteries. The drill is primed to operate efficiently after each charge using integrated electronics in the battery, motor, and charger.
As well, the RedLithium batteries serve to protect the drill against overheating and misuse. You’ll find that Milwaukee’s batteries may last longer because of these built-in protections.
This brushless drill is a reasonably priced yet powerful option, featuring 340UWO of power. The battery is twenty volts, a massive power source that allows for a long run-time.
Despite the impressive battery strength, the DeWALT brushless is not heavy. It is actually one of the lightest compact brushless drills around. However, DeWALT does offer batteries with higher Ah to improve tool run-times.
Another feature of this drill is the LED light with trigger-delay. The light stays on for twenty seconds after you’ve let go of the trigger, useful in dark basements or underneath a vehicle.
Combines power and run-time for more drilling, driving and fastening tasks in wood, metal, and masonry. Electronically controlled and engineered for longer run time, increased power and speed, and longer tool life. The variable 2-speed brushless motor delivers up to 2,000 RPM and 530 in.lbs. of max torque for efficient fastening. Weighs only 4.2 pounds (with battery) with an LED light that illuminates the job area for applications in dark spaces.
Due to declining costs and better performance, brushless motors are gaining in popularity in many applications. But there are still places where brushed motors make more sense. Much can be learned by looking at the adoption of brushless motors in automobiles.
As of 2021, most motors that are running whenever the car is running – things like pumps and fans – have moved from brushed motors to brushless motors for their increased reliability. The added cost of the motor and electronics more than makes up for the lower rate of field failures and decreased maintenance requirements.
On the other hand, motors that are operated infrequently – for example, motors that move power seats and power windows – have remained predominately brush motors. The reasoning is that the total run time over the life of the car is very small, and it is very unlikely that the motors will fail over the life of the car. As the cost of brushless motors and their associated electronics continues to decrease, brushless motors are finding their way into applications that have traditionally been held by brushed motors. As another example from the automotive world, seat adjustment motors in high end card have been adopting brushless motors because they generate less acoustic noise.