What Is A Brushless Motor?

Brushless Impact Driver

To have a better understanding of what a brushless motor is, it would be best to discuss its predecessor, the brushed motor, and how it worked. Brushed motors are representative of typical DC motors. It has permanent magnets on the outside and a spinning armature on the inside. The permanent magnets are also called the stator because they remain stationary. The armature is in constant rotational motion and is called the rotor.

Inside the armature is an electromagnet which generates a magnetic field once electricity courses through it. A brushed motor uses a commutator. What is a commutator? It is an attachment connected to the motor where electrical connection is made and ensures the current that flows in direct current.

The magnetic field attracts and repels the magnets in the stator and causes the armature to spin 180 degrees. In order to keep the armature spinning, you have to alter the poles of the electromagnet. The brushes make contact with two spinning electrodes in the armature so it can switch the magnetic polarity of the electromagnet as it spins.

Although it is cheap and easy for manufacturers to set up a brushed motor, it can present a host of problems:

  • The brushes are subject to wear out eventually;
  • Sparking and electrical noise are constantly generated as the brushes are making and breaking connections;
  • ​The brushes controls the maximum speed that can be achieved by the equipment;
  • ​Because of its central location in the motor, it is difficult to cool down the electromagnet;
  • Brushes exact a limit on the number of poles the armature can have.

Technology and the introduction on power transistors gave manufacturers a way to remove the brushes. This started the development process for brushless motors.

Difference Between Brushed And Brushless Motor

The main difference between brushed and brushless motor is that with the latter the permanent magnets are located on the rotor while the electromagnets are transferred to the stator. A computer replaces the commutator and is connected to high-power transistors which charge the electromagnets whenever the shaft turns.

A dc brushless motor has the following advantages over the brushed variety:

  • It is more precise because it is controlled by computers;
  • A brushless motor does not create sparking or too much noise;
  • ​Having the electromagnets relocated at the stator instead of the centre of the motor makes it much easier to cool down;
  • ​By going with brushless tools, you have the option of adding more electromagnets on the stator for improved efficiency.

The only disadvantage of the brushless motor is that it is more expensive. However you can easily cover the cost of the investment by constantly generating cost savings because you gain more efficiency from using a brushless tool like a drill.

Despite the cost, brushless motors are slowly replacing brushed motors because of it better efficiency, smoother torque, higher level of durability and its ability to speed up operations.

Applications Of The Brushless Motor

The advantages of choosing brushless over brushed as previously discussed have made it applicable to operate small battery-powered tools because these factors help extend its battery life.

Small scale appliances that are produced in large volumes greatly benefit from the use of the brushless motor. A good example would be the robotic vacuum cleaner. By being brushless, it allows for bi-directional operation and makes it possible for the appliance to run effectively while emitting low noise.

The brushless motor is also applicable to power tools.

What are the advantages of brushless power tools?

A brushless power tool is low in weight but is capable of generating high power output. Handheld power tools such as snow blowers and chainsaws have light weight components like rotary parts and slip rings and benefit from the increased power output of brushless technology.

Even though going brushless is comparatively expensive, because small appliances are manufactured in volume, economies of scale allow the prices of these items to remain affordable. You will be able to purchase and use high powered tools that are very energy efficient and will not break your bank account.

Other appliances and equipment that have gone brushless include hard drives, pumps, electric fans, coffee makers, hair dryers, mixers and CD or DVD players.

Brushless vs. Brushed: Which One Is The Better Choice?

Companies promote devices that use brushless as “smart tools”. This is because its electronics communicate directly with the stationary windings which allow a tool or equipment that goes brushless to adjust and accommodate the task.

A good example of this “smart feature” is when you try to drive a brushless drill into a material with a soft surface such as Styrofoam. The brushless drill will sense the material has less resistance and will only draw enough power from the battery to get the job done.

By contrast, if you were to use the same brushless drill to a board made of a hard material such as Mahogany, it would draw more current from the battery in order to penetrate the surface.

A brushless tool’s power can also be modified or adjusted to become stronger. How? Because its copper windings are located on the outside of its configuration which gives it more room to become larger.

Brushed tools tend to drag against the spinning commutator. This creates friction and instances when the voltage drops and the tool or equipment loses more power or experiences a continuous loss of energy while in use. With a computer in place of a commutator, these occurrences are not likely with a brushless power tool.

However as we mentioned earlier, a brushless motor greatly benefits devices or tools that are manufactured in large volumes. They are able to reap the advantages of efficiency and greater power output without affecting the cost of the item.

Such is not the case with power tools that are not commonly purchased. The use of brushless will have an inflationary effect on its price. Although the obvious trade- off is better performance, you will have to determine whether the extra expense will be worth it.

About the Author Randy Thompson

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