Nowadays, when you’re looking for power tools, you have a choice between two types, one with a brushed motor or one with a brushless motor. Brushed motors are traditional motors that have been around for a long time whereas brushless motors are more recent. Both of them exist in AC as well as DC configurations.
Let’s look at the differences between them by first describing brushed motors and then brushless motors. We’ll then see what the advantages of brushless motors are and whether you should buy brushless tools or not.
What is a Brushed Motor?
A brushed motor is made up of two parts and four major components:
- The first part is the stator. It is made of stationary coils or permanent magnets that are charged oppositely. They provide a rotating magnetic field that drives the rotating armature.
- That rotating armature is the second part of the motor, called the rotor. It acts as an electromagnet when power is applied and it is usually made of copper coils.
- The commutator is fixed to the armature coils and spins with it and the motor shaft. It is a rotary electrical switch.
- The brushes are stationary. Their job is to deliver the electrical charge to the commutator, with which they are held in contact thanks to springs.
The two brushes deliver an opposite charge to the commutator. Because the commutator is a split ring, each brush is in contact with it for a half turn (180°), in the case of a simple two-pole motor. Therefore, each brush delivers its charge for half the rotating time.
When brush + is powering the armature, the electromagnetic field attracts the charged coil of the armature towards the negatively charged (-) stator coil or permanent magnet.
Then brush – gets in contact with the commutator, creating a polarity reversal. The other coil of the armature is now negatively powered and it thus gets attracted towards the positively charged (+) stator coil or magnet.
The first rotation is now complete. This process then repeats itself hundreds or even thousands of times per minute depending on the motor or the selected speed setting.
This key operating principle allows motors to convert electrical energy into mechanical energy through rotating movement. This can then be used for the propulsion of objects.
What is a Brushless Motor?
With its different set-up, a brushless motor works differently than a brushed motor:
- The permanent magnets are now placed on the inside and they become the rotor.
- The stator is now made of the copper coils of the armature. They are fixed on the outside.
- The commutator and brushes are suppressed. They are replaced by an electronic controller that coordinates the delivery of electrical charges to the windings.
Instead of using a mechanical system to power the coils one after the other, brushless motors use electronic communication. They produce a three-phase variable frequency current that alternately feeds the windings, creating a rotating field that makes the rotor spin. It is the electronic controller that regulates the current being delivered to the coils. And it does it very precisely because it knows the position of the magnets at all times.
Also, as there is direct communication between the electronics and the static windings, the motor is capable of adapting itself to the task it is performing. It means that a brushless power tool can “feel” the resistance of the material and thus “choose to” pull more or less power. No wonder why tool companies market these as “smarter” tools!
Advantages of Brushless Motors
There is a bunch of other benefits that come with the use of a brushless motor and much of it has to do with the absence of a commutator and brushes.
First, brushless motors are more energy-efficient and can be more powerful:
- Brushes dragged against the commutator create friction. This results in losses of power and speed, and voltage drop. There is no such friction with brushless motors.
- Manufacturers say that the absence of friction increases substantially the operating time and battery life of their power tools.
- As the windings are positioned on the outside, there is more room for them. Thus, they can be made larger.
Their reliability is greatly improved:
- Without brushes and commutators, brushless motors have much fewer wearing parts. This means that the probability of motor malfunction is virtually zero and its lifetime is extended. The only wearing parts remaining are essentially the bearings.
- With friction comes heat. Because a brushless motor doesn’t produce friction, it won’t be overheating. It also won’t produce sparks, thus reducing fire hazards
They are also more comfortable to use:
- As there is much less friction, less noise and vibration are being produced.
- Brushless motors are more compact and two to three times lighter than brushed motors.
Brushed or Brushless – Should You Buy a Brushless Motor Tool?
You’ve just read about the numerous advantages that brushless motors have over brushed motors. And, although all these benefits may sound like a no-brainer in favor of brushless power tools, there’s one important thing you should consider before buying them: their price.
It costs about 30% more for manufacturers to produce brushless tools than to make standard tools. The price of these tools is therefore much higher in stores too.
That makes brushless power tools quite attractive to contractors and pro handymen as they will probably use them every day. But if you’re an occasional DIYer, you better ask yourself whether you truly need such a tool. Are the benefits worth the money? You be the judge!