Brushed DC Motor Manufacturers

DC brushed motor industry knowledge Q&A

I. What is a DC brushed motor?

A DC brushed motor is an electric device that converts DC power into mechanical energy. It relies on the synergy of brushes and commutators to achieve current commutation, thereby ensuring that the motor rotates continuously and stably. It has a long history of development in the field of motors and is a relatively mature type of motor with wide applications in many industries and scenarios. From large industrial equipment to small household appliances, it can be seen, providing power support for various equipment.

II. What physical laws are the working principles of DC brushed motors based on?

The working principle of DC brushed motors is mainly based on the law of electromagnetic induction and Ampere's law. The law of electromagnetic induction reveals the phenomenon that a changing magnetic field can generate an electric field, while the Ampere's law describes the force that a current-carrying conductor will be subjected to in a magnetic field. When a DC power supply is connected to the motor, the current enters the rotor winding through the brush. In the magnetic field generated by the stator, the energized rotor winding is subjected to the electromagnetic force according to the Ampere's law, thereby generating electromagnetic torque and driving the rotor to rotate. At the same time, the commutator causes the direction of the current to change continuously to maintain the continuous rotation of the rotor. This process fully reflects the application of these two physical laws. ​

III. What specific role does the commutator play in the working process of the DC brush motor? ​

The commutator is a crucial component in the DC brush motor. It consists of multiple commutator segments and is closely connected to the rotor. When the motor is running, as the rotor rotates, the commutator will continuously change the direction of the current in the rotor winding. This is because when the rotor rotates to a certain angle, if the direction of the current does not change, the direction of the electromagnetic force on the rotor will reverse, causing the motor to be unable to rotate continuously. The timely commutation of the commutator can ensure that the direction of the electromagnetic force on the rotor at each position remains consistent, and always drives the rotor to rotate in one direction, thereby ensuring that the motor can work continuously and stably. For example, in the motor of a toy car, it is precisely relying on the role of the commutator that the wheels of the toy car can continue to rotate forward. ​

IV. What are the types of stators of DC brush motors and what are their characteristics?​

There are two main types of stators for brushed DC motors, namely permanent magnet stators and iron core stators with windings. Permanent magnet stators use permanent magnets to generate magnetic fields. They have a relatively simple structure, low manufacturing cost, and do not require additional excitation current. They have high energy efficiency and are commonly found in small brushed DC motors, such as electric toothbrushes and small fans. However, the magnetic field strength of permanent magnets is affected by environmental factors such as temperature. Long-term use in high-temperature environments may cause demagnetization, thereby affecting the performance of the motor. Iron core stators with windings generate magnetic fields by winding windings on the iron core and passing current. The magnetic field strength of this stator can be controlled by adjusting the winding current. It has high flexibility and is suitable for occasions with high requirements for magnetic field strength, such as some industrial speed-regulating motors. However, its structure is relatively complex, the manufacturing cost is also high, and an additional excitation power supply is required to provide current. ​

V. What materials are brushes generally made of, and what effects will their wear have on the motor?​

Brushes are generally made of materials such as graphite. Graphite has good conductivity and lubricity, which can ensure the smooth transmission of current and reduce friction with the commutator. During operation, the brushes will gradually wear out due to continuous friction with the commutator. When the brushes are worn to a certain extent, they will have many adverse effects on the motor. First, the contact between the brush and the commutator will become unstable, resulting in poor current transmission, which will reduce the output power of the motor and unstable operating performance. For example, if the brushes of the vacuum cleaner motor are severely worn, the suction will be significantly weakened. Secondly, the worn brushes may produce large sparks, increase electromagnetic interference, and affect the normal operation of surrounding electronic equipment. In addition, if the severely worn brushes are not replaced in time, it may cause poor contact between the brush and the commutator, or even a circuit breaker, making the motor unable to work properly. At the same time, the powder produced by wear may also contaminate other parts inside the motor and affect the service life of the motor. ​

VI.In which application scenarios is the advantage of the large starting torque of the DC brushed motor specifically reflected? ​

The advantage of the large starting torque of the DC brushed motor is clearly reflected in many scenarios that require rapid start-up and drive large loads. For example, in a crane, when a heavy object needs to be lifted, the motor must generate a sufficiently large torque in a short time to overcome the gravity of the heavy object so that the heavy object can start and rise smoothly. This feature of the DC brush motor just meets the working requirements of the crane. In an electric forklift, the motor is also required to have a large starting torque to drive the forklift and the goods carried to start quickly and improve work efficiency. In addition, in some large industrial equipment, such as the auxiliary transmission system of a rolling mill, the motor is also required to start quickly and provide a large torque to ensure the normal operation of the equipment. ​

VII. What equipment will the electromagnetic interference of the DC brush motor affect, and how to reduce this interference? ​

The electromagnetic interference of the DC brush motor is mainly generated by the spark between the brush and the commutator. This interference may have adverse effects on a variety of surrounding electronic devices. For example, in the medical field, some precision medical equipment such as electrocardiographs and monitors have very high requirements for the electromagnetic environment. The electromagnetic interference generated by the motor may cause inaccurate measurement data of these devices and affect the diagnosis results. In the field of communications, radio communication equipment, satellite receiving equipment, etc. are also susceptible to electromagnetic interference, resulting in a decrease in signal transmission quality, signal interruption, noise and other problems. In order to reduce this interference, some measures can be taken, such as adding a shielding layer to the motor housing, which can block the propagation of electromagnetic signals; installing filters on the power supply line of the motor to filter out interference signals; selecting high-quality brushes and commutators to reduce the generation of sparks; reasonably arranging the distance between the motor and other electronic equipment to avoid close-range interference, etc. ​

VIII. According to the stator magnetic field generation method, DC brush motors can be divided into which two categories, and what are their application scenarios? ​

According to the stator magnetic field generation method, DC brush motors can be divided into permanent magnet DC brush motors and wound DC brush motors. The stator of the permanent magnet DC brush motor uses permanent magnets to generate a magnetic field. It has a simple structure, small size, light weight, high efficiency, and does not require excitation current, and has good dynamic performance. It is widely used in small devices and cost-sensitive scenarios, such as small household appliances (electric toothbrushes, hair dryers), electric toys, portable electronic devices, etc. The stator of a wound DC brushed motor generates a magnetic field through the winding, and the magnetic field strength can be precisely adjusted by controlling the winding current, thereby achieving flexible control of the motor speed and torque. However, this type of motor has a relatively complex structure, high cost, and requires an additional excitation power supply. It is mainly used in industrial fields that require high motor performance and require precise control, such as machine tools, rolling mills, cranes and other large industrial equipment. ​

IX. What is the difference in performance between shunt-excited DC motors and series-excited DC motors, and what occasions are they suitable for? ​

The stator winding and rotor winding of a shunt-excited DC motor are connected in parallel, and its speed is relatively stable, less affected by load changes, and has good speed regulation performance. When the load changes, its speed will not fluctuate too much, and it can maintain a relatively stable operating state. It is suitable for occasions where a stable speed needs to be maintained under different loads, such as machine tools, fans, water pumps and other equipment. These devices have high requirements for the stability of the speed to ensure processing accuracy or work efficiency. The stator winding and rotor winding of the series-excited DC motor are connected in series. It has a large starting torque and strong overload capacity, but the speed varies greatly with the load. When the load increases, the speed will drop sharply. This characteristic makes it suitable for occasions that require a large starting torque, such as power tools (electric drills, electric saws), cranes, trams, etc. For example, an electric drill needs to overcome a large resistance when starting, and the large starting torque of the series-excited DC motor can meet its working needs. ​

X. What are the advantages and disadvantages of DC brushless motors compared with DC brushless motors? What factors should be considered when choosing? ​

The advantages of DC brushless motors are simple control, low cost of corresponding control circuits, relatively mature technology, and advantages in some cost-sensitive occasions. However, it has the problem of brush wear and needs regular maintenance and replacement, which not only increases the cost of use, but also may increase downtime. In addition, the sparks generated between the brush and the commutator will cause electromagnetic interference, affecting surrounding electronic equipment, and the life is relatively short. DC brushless motors have no brushes, so there is no problem of brush wear, small electromagnetic interference, low noise, long life, and more stable and reliable operation. However, its control circuit is complex and requires a special controller, which is costly. When choosing, multiple factors need to be considered, such as the cost sensitivity of the application scenario, the requirements for motor life and maintenance, and whether there are restrictions on electromagnetic interference. For example, in ordinary electric toys, DC brushed motors are a more suitable choice because they are more sensitive to cost and the motor usage intensity is relatively low; while in quadcopters, in order to pursue long life, low interference and high stability, DC brushless motors are usually selected. ​

XI. Compared with AC motors, what are the advantages and disadvantages of DC brushed motors, and what different scenarios are suitable for them?

The advantage of DC brushed motors is that they have good speed regulation performance, can achieve smooth speed regulation in a wide range, and have large starting torque. They can accurately control speed and torque. They are suitable for scenarios with high requirements for speed and torque control, such as precision transmission equipment in industrial automation production lines, medical devices that require precise speed control, etc. Its disadvantages are that the structure is relatively complex, there are brush wear problems, the maintenance cost is high, and in high-power applications, the efficiency is relatively low. The advantages of AC motors are simple structure, easy maintenance, and low cost. They are widely used in high-power applications with low speed requirements, such as large industrial fans, water pumps, central air-conditioning compressors, and other equipment. These devices do not require high speed regulation, but focus more on the reliability and low-cost operation of the motor. In some small devices or precision instruments that require precise control of speed and torque, brushed DC motors can better play their advantages. ​