Brushed or brushless? It’s a question that will pop up when you’re looking at electric power tools, kitchen appliances and other bits of equipment. The answer, in the main, is that brushed motors are more common and cheaper while brushless models are generally more expensive. The reason for this is that brushless motors have more complex mechanical structures – and are therefore more expensive to produce. But it’s also because they’re more efficient and use less energy to drive the motor. So which is best for you? We’ve rounded up the facts to help you decide.
Brushed motors (also known as DC or brushed) use stationary brushed or brushless wire brushes that contact the rotor to create an electromotive force that causes it to rotate. The brushes are made of a material that conducts electricity well but is soft enough to rub against the spinning commutator without wearing it away. This is important because the rotor must be spun continuously in order to generate enough force to do any work. The commutator (shown in the image above) is designed to ensure that the magnetic poles of the permanent magnets always align with the electrical current, causing either attraction or repulsion. As the rotor spins, the commutator reverses the direction of the current several times per revolution to maintain the electromotive force and keep the rotor rotating.
The downside of brushed motors is that the brushes and commutator can wear down over time, reducing the life of the motor. Also, a portion of the electricity that powers the motor is lost in friction between the brushes and commutator.
This means that a brushed motor uses a larger amount of electricity than it should to do the same work as a brushless one. Brushless motors are more efficient and therefore more economical as they don’t lose as much of the electricity to friction.
They also run cooler, which is an important consideration because excessive heat can damage the motor and battery. A brushless motor can also be more reliable than a brushed model because there is no need for brushes to wear down, and a brushless model doesn’t need a commutator that can fail over time.
Today, brushless motors are used almost everywhere that needs a DC motor. They are found in electronics devices such as electric cars and drones, as well as household appliances like washing machines, air conditioners and electrical fans. Brushless motors are also used in applications such as servos and robotics, where the precise control of each rotor is essential. Brushless motors can be controlled by a variety of mechanisms, including Hall Effect ICs that monitor feedback signals from the rotor to detect its rotation speed. This information is fed back to the controller which adjusts the voltage to the rotor, keeping it at a constant speed.