Brushed Vs Brushless Motors: When and Why to Choose One Over the Other？

Introduction Of Brushed and Brushless Motors

1.In our real life, many motion control systems will be applied to DC motors. Compared with AC motors, people will think that DC motors are easier to control, so when they are applied to control torque, speed or position, many people mostly Will be more willing to choose a DC motor.

2.DC motors are also divided into the following two types: brushless motors and brushed motors. The difference between the two can also be seen from the name. The brushless motor uses the electronic control principle to replace the original mechanical commutation function. The DC brushed motor has brushes, which can be

3. controlled by the motor to change the direction.

In many applications, brushed or brushless DC motors can be used. Their function is based on the same principle of attraction and repulsion between coils and permanent magnets. Both have pros and cons, and you may choose one over the other depending on the requirements of your application.

Brushed and Brushless Motors: Advantages and Disadvantages

This article will make some simple summaries to give you a basic idea of whether to choose a brushless motor or a brushed motor in the application. The following table summarizes the main advantages and disadvantages of the two motors. The information is for reference only:

1. Lifetime

As previously mentioned, one of the disadvantages of brushed motors is that there is mechanical wear of the brushes and commutator. Carbon brushes in particular are sacrificial, and in many motors they are designed to be replaced periodically as part of a maintenance program. The soft copper of the commutator is also slowly worn away by the brushes, and eventually reach a point where the motor will no longer operate. Since brushless motors have no moving contacts, they do not suffer from this wear.

2. Speed and Acceleration

Brushed motors rotational speed can be limited by the brushes and commutator, as well as the mass of the rotor. At very high speeds, the brush to commutator contact can become erratic, and brush arcing increases. Most brushed motors also use a core of laminated iron in the rotor, which gives them large rotational inertia. This limits the acceleration and deceleration rates of the motor. It is possible to build a brushless motor with very powerful rare earth magnets on the rotor, which minimizes the rotational inertia. Of course, that increases the cost.

Electrical Noise

The brushes and commutator form a kind of electrical switch. As the motor turns, the switches are being opened and closed, while significant current is flowing through the rotor windings, which are inductive. This results in arcing at the contacts. This generates a large amount of electrical noise, which can get coupled into sensitive circuits. Arcing can be somewhat mitigated by adding capacitors or RC snubbers across the brushes, but the instantaneous switching of the commutator always generates some electrical noise.

Acoustic Noise

Brushed motors are “hard switched” – that is, current is abruptly moved from one winding to another. The torque generated varies over the rotation of the rotor as the windings get switched on and off. With a brushless motor, it is possible to control the winding currents in a way that gradually transitions current from one winding to another. This lowers torque ripple, which is a mechanical pulsation of energy onto the rotor. Torque ripple causes vibration and mechanical noise, especially at low rotor speeds.

Cost

Since brushless motors require more sophisticated electronics, the overall cost of a brushless drive is higher than that of a brush motor. Even though a brushless motor is simpler to manufacture than a brushed motor, since it lacks brushes and a commutator, brushed motor technology is very mature and manufacturing costs are low. This is changing as brushless motors become more popular, especially in high volume applications like automotive motors. Also, the cost of electronics, like microcontrollers, continues to decline, making brushless motors more attractive.

Summary

Because of cost and performance considerations, everyone will choose brushless motors, which has led to the application of brushless motors in many fields. Of course, brushed motors are also used in some places.

Much can be learned by observing the adoption of brushless motors in automobiles. As of 2020, most motors that run while the car is running, such as pumps and fans, have moved from brushed to brushless motors to improve reliability. The additional cost of the motor and electronics more than makes up for the lower field failure rate and reduced maintenance requirements.

On the other hand, motors that run infrequently—for example, those that move power seats and power windows—are still mostly brushed motors. The reason is that the total running time of the car over its lifetime is very small and the chances of the motor failing over the lifetime of the car are very small.

As the cost of brushless motors and their associated electronics continues to drop, brushless motors are finding their way into applications traditionally occupied by brushed motors. Taking the automotive example again, seat-adjustment motors in high-end cards have been using brushless motors because they produce less noise.