There are many types of motors , including brushed motors and brushless motors. In previous articles, we've introduced the basics of both brushed and brushless motors. To enhance your understanding of brushed and brushless motors, this article will discuss the performance differences between them. If you're interested in motor-related knowledge, please continue reading.
I. Brushed Motor
A brushed motor is a rotating electric motor that converts electrical energy into mechanical energy (electric motor) or mechanical energy into electrical energy (generator) by containing brushes. Brushed motors are the foundation of all motors, characterized by fast starting, timely braking, smooth speed adjustment over a wide range, and relatively simple control circuitry.
II. Brushless Motor
A brushless DC motor consists of a motor body and a driver, and is a typical mechatronic product. Because brushless DC motors operate under self-control, they do not require an additional starting winding on the rotor like synchronous motors that start under heavy loads with frequency conversion speed regulation, nor do they experience oscillations or loss of synchronism during sudden load changes. The permanent magnets in small and medium-capacity brushless DC motors now mostly use high-energy-level rare-earth neodymium iron boron ( Nd-Fe-B ) materials. Therefore, the size of a rare-earth permanent magnet brushless motor is one frame size smaller than that of a three-phase asynchronous motor of the same capacity.
III. Performance differences between brushed motors and brushless motors
1. Brushed motors have a simple structure and mature technology.
As early as the 19th century, when electric motors were invented, the first practical motors were brushless, namely AC squirrel-cage induction motors. These motors were widely used after the advent of AC power. However, induction motors have many insurmountable drawbacks, which has slowed the development of motor technology. In particular, DC brushless motors were unable to be commercially deployed for a long time. With the rapid development of electronic technology, they have only gradually entered commercial operation in recent years, and in essence, they still belong to the category of AC motors.
Not long after the invention of brushless motors, brushed DC motors were invented. Because brushed DC motors have a simple structure, are easy to manufacture and process, are convenient to maintain, and are easy to control ; DC motors also have the characteristics of fast response, large starting torque, and the ability to provide rated torque from zero speed to rated speed, so they have been widely used since their introduction.
2. DC brushed motors have a fast response speed and high starting torque. They offer smooth speed change with almost imperceptible vibration from zero to maximum speed and can handle larger loads during startup. Brushless motors, on the other hand, have high starting resistance (inductive reactance), resulting in a low power factor, relatively low starting torque, a buzzing sound, and strong vibration during startup, and can handle smaller loads during startup.
3. Brushed DC motors operate smoothly with good starting and braking performance. Brushed motors regulate speed through voltage adjustment, resulting in smooth starting and braking, as well as smooth operation at constant speed. Brushless motors, on the other hand, are typically controlled by digital frequency converters. They first convert AC to DC, then back to AC, controlling the speed through frequency changes. Therefore, brushless motors experience less smooth operation and greater vibration during starting and braking; they only become smooth when the speed is constant.
4. High Control Precision of DC Brushed Motors: DC brushed motors are typically used in conjunction with gearboxes and decoders, resulting in higher output power and control precision, reaching up to 0.01 mm. This allows moving parts to stop at virtually any desired location. All precision machine tools utilize DC motors for control precision. Brushless motors, due to their uneven start-up and braking, cause moving parts to stop at different positions each time, requiring locating pins or limit switches to bring them to a desired stop.
5. DC brushed motors have low operating costs and are easy to maintain. Due to their simple structure, low production costs, numerous manufacturers, and relatively mature technology, DC brushed motors are widely used in factories, machine tools, and precision instruments. If the motor fails, only the carbon brushes need to be replaced, and each carbon brush costs only a few yuan, making them very inexpensive. Brushless motors, on the other hand, have less mature technology, higher prices, and limited applications. They are mainly used in constant-speed equipment, such as variable frequency air conditioners and refrigerators. When a brushless motor fails, it must be replaced.
6. Brushless and low-interference: Brushless motors eliminate the brushes, and the most direct change is the elimination of the electrical sparks generated when a brushed motor is running. This greatly reduces the interference of electrical sparks on remote control wireless equipment.
7. Low noise and smooth operation: Brushless motors have no brushes, which greatly reduces friction during operation, resulting in smoother operation and much lower noise. This advantage is a huge support for the stability of model operation.
8. Long lifespan and low maintenance cost: With fewer brushes, the wear of brushless motors is mainly on the bearings. From a mechanical point of view, brushless motors are almost maintenance-free motors. When necessary, only some dust removal maintenance is required.
