Significant differences exist when dealing with brushed vs brushless motors. Because of this, brushless motors have been dominating the industry for several years.
Many cordless power tools are now brushless rather than brushed. But what does this mean? And is it important?
The answer to these questions will impact your decision on which tools to buy and use. Don’t be fooled by fancy marketing and price tags. Within this article I debunk the exact differences between brushed vs brushless. I also go into what impact this has on performance.
What’s the difference between Brushed and Brushless?
10 second summary
A brushed motor has carbon brushes which physically touch a commutator ring. As the shaft of the motor turns, the commutator ring turns and the brushes have contact with the commutator the whole time.
Unlike a brushed motor, brushless motors offer no brushes or friction. The motor is controlled by an electronic sensor. The sensor controls magnetic fields and allows the motor to go.
We need to look at the differences in technology to understand why big performance differences exist between brushed and brushless motors. Through understanding the mechanisms of these two motors the performance differences become clear.
Brushed Motors
A brushed motor is wired directly to DC power and is often called a “Brushed DC motor”. They have permanent magnets on the outside of the structure called ‘the stator’. These magnets are oppositely charged and are attracted to each other. The stator holds permanent charge.
There is a spinning armature on the inside which contains an electromagnet called ‘the rotor’. A DC motor keeps the opposite charge of the rotor attracting the stator so that there is a constant pull forward.
Brushes (often made from Carbon) make constant contact with the commutator which provides magnetic polarity to the rotor. The brushes are two fixed electrodes rubbing against the commutator ring as it spins with the rotor.
A current is run to the armature as the rotor spins 180 degrees. Then the poles of the electromagnet flip causing the brushes to make contact with the stator. This causes a flip of the magnetic field allowing the rotor to spin a full 360 degrees.
What are they used for?
Brushed motors are commonly found in your home. Wherever there is a need to convert electricity into rotational motion, you’ll probably find a brushed DC motor.
One example is in power tools. Brushed motors have traditionally been used until recent years. This is just one particular use of brushed DC motors. Electric toothbrushes, RC toy cars and electric recliner chairs all use brushed motors.
DC brushed motors are also used in larger machines such as cranes, drills and steel rolling mills.
Brushless Motors
A brushless motor, as expected, does not feature brushes within its mechanism. In design they are almost a flipped version compared to brushed motors.
In brushless DC motors, the permanent magnets are on the rotor rather than the stator. And the electromagnets are on the stator rather than the rotor.
Brushless motors do not require brushes (or fixed electrodes) to flip the electromagnetic field to make the motor turn. Rather, a computer charges electromagnets in the stator to rotate the rotor the full 360 degrees. A sensor is also required to detect the angle of the rotor in order to tell the computer whether to reverse the direction of the current to create torque in one direction. This also removes the need for a physical commutator.
Since the electronics communicate with the stationary elements of the motor, this allows tools to adjust according to the task at hand. Some companies market brushless motors as “smart” tools. This means more power is delivered when needed.
What are they used for?
Brushless motors are often found in electronic devices that are in constant or regular use. For example, washing machines, fans and air conditioners use brushless motors. This is because brushless motors are more efficient. This makes a significant impact in power consumption in devices used regularly.
Other examples include electric vehicles. This is because brushless motors have the ability (through the sensor) to deliver controlled power. This is essential as cars need to deliver a smooth and precise amount of power and speed to the wheels. Otherwise it wouldn’t be possible to cruise at a constant speed.
Brushless motors are also now used in some power tools. Brushless motors are still less common than their brushed DC motor equivalents. This is due to increased costs and complexities to manufacture. However brushless motors are increasing their application and it’s likely more and more manufacturers take advantage of brushless technology.
Are Brushless tools worth the extra expense?
Price is a major factor in deciding which power tool to buy. Because of the technology brushless motors offer, they are far more expensive compared with a brushed power tool. The most expensive part of a brushless motor is the sensor.
Because of this, brushless power tools are around 50% more expensive. It’s important to look at the advantages on offer.
Power
Brushless tools provide more power than their brushed motor equivalents. This is because there is far less resistance in the brushless motor.
In a brushed motor, there is a constant contact point between the brush and rotor. This is because more energy is used to power the machine and less energy is spent on friction.
Brushless motors will also offer more power when needed. They can sense when to ease up on the power or deliver more.
Battery Life
Brushless motors are far more efficient than brushed motors. There is a significant impact on battery life since the motor is operating more efficiently.
When converting electricity into power, brushless motors are far more efficient. More of the total power used by the motor is being turned into rotational force and less is being lost as heat. Brushed tools feature carbon brushes which are in constant friction. This causes inefficiencies within the motor and energy is lost as heat.
In general, a brushless motor is 85% to 95% efficient whereas a brushed motor is around 75% to 80% efficient. A brushless motor only spends energy where necessary as it can ‘sense’ how much energy is needed. With the combination of this, a brushless motor can do twice the amount of work with the same battery. The below video demonstrates this with two otherwise identical tools:
Maintenance & Tool Life
Maintenance can be a significant factor when considering larger machinery. The lifespan of a brushed motor is limited by the brush type. Normally their lifetime is between 1,000 to 3,000 hours.
This is due to the brush of the motor wearing out and needing to be replaced. It is possible to maintain brushes within the motor to prolong its life. This involves regularly servicing and cleaning the brushes.
Brushless motors can attain tens of thousands of hours of run time and do not require maintenance. Since there are no brushes to wear and there is little to no friction, the lifetime of the machine is far greater.
‘Smartness’
Brushed motors always operate as fast as possible whilst in use. This means that there is no thought process or intelligence contributed to the task at hand.
For example, if a screw was being drilled into a wooden block there would be one power setting: as fast as possible.
By contrast a brushless motor has a computer which adjusts according to the task at hand. For example, if the tool detects a lack of resistance, power consumption would be reduced. If the user was drilling into concrete, more torque would be given and more power consumed. This improves battery life but also reduces wear and tear on the machine.
Summary
In our view brushless tools are absolutely worth the additional expense compared to brushed. Although you may end up spending 50% more on the original tool, it will last far longer, cost you less to run and maintain and deliver much higher quality results.
Here is a summary table I’ve put together on the benefits brushless motors offer:
