Two of the most common DC electric motors in use today are brushed and brushless DC motors. Both motors have the same fundamental idea of using electromagnetism to provide mechanical rotations. But with different design concepts, brushed and brushless motors are bound to have their differences in performance, cost, and maintenance.
So what motor design is better—brushed or brushless?
How Does a DC Electric Motor Work?
Electric motors convert electricity into mechanical energy. They do this by allowing electricity to pass through copper windings, creating an electromagnetic field that excites the permanent magnets inside the motor, causing the rotor to move and produce mechanical energy.
Although both brushed and brushless motors have the same goal of converting electricity to mechanical energy, their designs are different. To understand their difference, let’s talk about motor design, starting with the brushed motor.
Brushed Motor Design
Brushed motors have been in production for over a century by now. They are known to have a simplistic design utilizing a pair of carbon brushes to deliver power to the motor. Brushed motors will always have four major parts, these are:
Stator: The stationary part of the motor. It contains the permanent magnets that make the rotor move. Rotor: The rotating part of the motor. It contains a copper coil that, when powered, makes the copper coil electromagnetic. Commutator: A metal ring that ensures the rotor keeps spinning by reversing the polarity for every half turn of the rotor. Brushes: A stationary part made of carbon directly connected to the terminals of the power source. They relay power to the commutator ring, which then activates the rotor.
A brushed motor uses brushes to electrically power the motor while allowing both rotor and commutator to rotate. The rotor is composed of copper windings that, when powered, basically become an electromagnet.
So what happens if two magnets get close together?
Well, depending on the alignment of the magnetic poles, they will either attract or repel each other. The goal of a brushed motor is to use attraction and repulsion to rotate the motor. This is where a commutator becomes useful.
A commutator is a metallic ring at the center of the rotor that switches the magnetic pole of the rotor every 180 degrees. This effectively ensures that the rotor’s magnetic pole always aligns with the same magnetic pole of the stator, causing repulsion.
The outcome? Continuous mechanical rotations have enough force to power your blender (or anything that uses a brushed motor).
Brushless Motor Design
Brushless motors started to gain popularity in the 1980s when transistors became more common in electronics. Having readily available solid-state components played a big role in making brushless motors applicable for power tools, home appliances, and electronics. Their complex yet efficient design gives brushless motors more torque than their brushed counterparts.
Brushless motor design employs several essential parts. They would include:
Stator: The stationary part of the motor. It contains several copper coils that, when powered, become an active magnet. Rotor: The rotating part of the motor. This contains the permanent magnets that get rotated due to the electromagnetic field between the stator and the rotor. Hall Effect Sensor: A sensor that detects which coils are energized and which coils are not. Control Circuit: An electronic circuit designed to decide which coils inside the stator to energize.
As the name implies, brushless motors don’t use brushes to power the motor. Brushless motors also don’t have current-carrying commutators. Instead, it uses a hall effect sensor and a control circuit to ensure the opposing magnetic poles of the stator and rotor always align. Another thing you’ll find different is that the stator houses the copper windings while the rotor houses the permanent magnets.
A brushless motor fundamentally works the same way as a brushed motor: using differences in magnetic poles to move the rotor, creating rotation and torque.
But without brushes and commutators, how can the copper windings get power?
Simple, you make the copper windings stationary. Brushes are no longer needed with stationary copper windings as you can directly power the coils through wires.
As for the commutators, a brushless motor uses a hall effect sensor and a control circuit. A hall sensor is a flat circular sensor placed beside the copper windings of the stator. Since the stator houses several coils, the hall sensor can detect whether one of these coils is energized or not.
The sensor then gives its reading to the control circuit and decides which coils to energize. So if the rotor’s permanent magnets get near the attracting magnetic poles, the control circuit will stop energizing these coils and energize the next coil that attracts the rotor’s permanent magnets. The control circuit will also energize the coils before the permanent magnets, causing repulsion and adding even more torque to the rotation.
Pros and Cons of Brushed and Brushless Motors
With the differences in motor design, both brushed and brushless motors will have pros and cons. Here is a table to help you understand their strengths and weaknesses:
Should You Buy Hardware With a Brushed or Brushless Motor?
As you can see in the table, brushless motors are better in every way (except in cost) than their brushed counterpart. They provide higher torque, faster speed acceleration, lower noise, and higher efficiency, and are more durable.
So when you get the chance to buy a new power tool, kitchen appliance, drone, or anything that needs a motor, choosing items with a brushless motor is generally the better option.
So should brushed motors be obsolete?
Well, no. Especially because a brushless motor (plus control circuit) will cost significantly more than an item using a brushed motor. And although a brushless motor is better than its brushed counterpart, it doesn’t mean a brushed motor is bad. In fact, a brushed motor is plenty good. You can achieve the same tasks with a brushed motor as people would with a brushless one.
In general, brushless motors are the ideal motors inside your tools and equipment. But there are also situations where you might want to use brushed motors instead. These situations would include:
When the motor is used in momentary short bursts (e. g. , blender, power seats, and windshield wipers) When a tool/appliance becomes useful only a few times a year When the task doesn’t require much torque (e. g. , toys, air vents) In extreme operating conditions. Brushed motors do not need sensors or control circuits that may fail in extreme weather conditions
Making Smart Purchases
Now that you understand the difference between brushed and brushless motors, hopefully, it makes it easier for you to make a smart purchase when buying kitchen appliances, tools, and equipment. This should also explain why some items are more expensive than their counterparts even though they come from the same brand, have the same features, and use the same form factor. Remember, just because you can buy a premium item using a brushless motor doesn’t always mean it’s the smart thing to buy.
