Introduction: DC motors are widely used in our daily life, from small household appliances to large industrial automobile equipment. There are a large number of DC motors. DC motors are generally divided into two categories: winding magnetic field DC motors and permanent magnetic field DC motors.
Brushed DC motors and brushless DC motors
As the two types of motors that are often mentioned, the biggest difference between the two is the brush. The brushed DC motor uses permanent magnetic force as the stator, the coil is wound on the rotor, and the energy is transmitted through the mechanical action of the carbon brush and the commutator machine. This is why it is called a brushed DC motor, while there is no mechanical component such as a commutator between the rotor and the stator of the brushless DC motor.
The decline of brushed DC motors is due to the fact that high-performance power devices as the switch of the motor are more practical, more economical and reliable in control mode, replacing the advantages of brushed motors. Second, brushless DC motors have no brush wear, and have more advantages in electrical noise and mechanical noise, energy efficiency, reliability and life.
However, brushed motors are still a reliable choice for low-cost applications. With the right controller and switch, good performance can be achieved. Since almost no electronic control devices are required, the entire motor control system will be quite cheap. In addition, it can save the space required for wiring and connectors, and reduce the cost of cables and connectors, which is very cost-effective in applications that do not require energy efficiency.
DC Motors and Drives
Motors and drives are inseparable, especially in recent years, market changes have put forward higher requirements for motor drives. First of all, there is a high requirement for reliability. Various protection functions are necessary, and built-in current limiting is required to control the current of the motor when the motor starts, stops or stalls. These are all enhancements in reliability.
High-efficiency drive control algorithms such as motor rotation digital control technology achieved through speed control and phase control, and high-precision positioning control technology required by actuators are indispensable for the development of high-performance motor application systems. This requires efficient drive control algorithms that designers can easily use.And now many manufacturers will directly hardware the algorithm and apply it to the driver IC, which is more convenient for designers to use. Convenient drive design is now more popular.
Stability also requires the support of driving technology. The optimization of driving waveform has a great impact on reducing motor noise and vibration. Excitation driving technology suitable for various motor magnetic circuits can greatly reduce the stability of motors when working. In addition, it is the continuous pursuit of lower power consumption and higher efficiency.
The role of half-bridge driving, a typical driving method for DC motors, is to generate AC trigger signals through power tubes, thereby generating large currents to further drive the motor. Compared with full-bridge, half-bridge driving circuits are relatively low in cost and easier to form. Half-bridge circuits are prone to waveform deterioration and interference between oscillation conversions. Full-bridge circuits are more expensive and more complex, and are not easy to produce leakage.
The popular PWM drive is already a widely used driving solution in DC motors. One of the reasons is that it can reduce the power consumption of the driving power supply and is increasingly widely used. Many motor PWM solutions now have achieved a high level in improving wide duty cycle, frequency coverage, and reducing power consumption.
When brushed motors are driven by PWM, the switching loss will increase with the increase of PWM frequency. When reducing current ripple by increasing frequency, it is necessary to balance frequency and efficiency. The sine wave excitation PWM drive of the brushless motor is also an excellent solution in terms of efficiency, although it is more complicated.
Summary
As the functional requirements of the terminal market change, the requirements for DC motor performance and energy efficiency are gradually increasing. Whether using a brushed DC motor or a brushless DC motor, it is necessary to select the appropriate drive technology according to the needs of the scene to achieve more reliable, stable and efficient motor operation.
