The main reason is that the energy density of brushed motors is higher than that of brushless motors. Not only brushed motors are used in power tools, but also the starting motors of automobiles and motorcycles are often used. Brushed motors are often used in the starting process of the two loads. It requires a very large starting torque, and the instantaneous starting current may exceed 10 times the rated current. The brushed motor has cost and volume advantages.
Advantages and disadvantages of brushed motors and brushless motors
The brushed motor used in general power tools is a series motor. This motor can be used for both AC and DC. The starting torque is very large, the speed is high, the speed adjustment is easy, the power supply is versatile, and the size is small. This feature is believed to be used. Anyone who has used power tools has experienced that things that are too heavy and too large are not easy to operate at all. The structure of this kind of motor is simple, so the production cost is relatively low, and the control circuit is also very simple.
However, this series motor is equipped with carbon brushes for phase commutation. The carbon brushes are wearing parts. After a period of use, the carbon brushes need to be replaced. If some dust or the like enters between the carbon brushes and the commutator, the wear will increase. And it rots easily. In addition, because of the existence of carbon brushes, there will be a certain noise at high speed, which is not very comfortable to use. The brushless motor uses electronic Hall elements to imitate the commutation of carbon brushes, so theoretically it can solve the problem of easy wear and tear of carbon brushes, which brings convenience and reliability to maintenance, and reduces noise a lot.
The brushless motor is essentially an AC motor. It needs to turn on the pulse voltage of each phase of the coil, so it needs a stable DC power supply on the bus to work. If there is no DC power, it needs to be rectified and turned into DC. It can be used, but the conduction between the control coils requires a lot of switches, and the acquisition and processing of Hall signals requires related circuits and control chips, because the control part of the brushless motor is much more complicated than the brushed motor, so the cost will be It is much more expensive, and the Hall has to be wired. If the line is broken, it will also affect the use.
Because the brushless motor is a mechatronics system, the volume is larger than that of the brushed motor, and because the torque and high-speed performance are different from the brushed motor, it is currently used in washing machines, exhaust fans, hair dryers, vacuum cleaners and other home appliances. , brushed motors are still used on a large scale.
Although brushed motors are currently used on a large scale in small equipment such as electric work, it cannot be ruled out that with future technological progress, brushless motors will still have the possibility of replacing brushless motors.
