In modern industry and daily life, motors play a crucial role, from driving large mechanical equipment to powering small household appliances, motors are everywhere. Understanding the principles and types of motors is essential for engineers, enthusiasts, and anyone interested in modern technology.
DC motors operate based on the principle that a current-carrying conductor experiences a force in a magnetic field. When DC current passes through the armature winding of the motor, according to the left-hand rule, the current-carrying conductor will experience an electromagnetic force in the magnetic field, which causes the armature to produce rotational motion. The armature winding cuts the magnetic lines of force, thereby generating an induced electromotive force, which is opposite to the direction of the armature current and is called back electromotive force. The speed of the DC motor is proportional to the applied voltage, and the torque is proportional to the armature current. Therefore, by adjusting the voltage, the speed of the motor can be controlled, and by adjusting the current, the torque of the motor can be changed.
Permanent Magnet DC Motor: This type of motor uses a permanent magnet as the stator magnetic field, eliminating the need for additional excitation current, simplifying the structure, and reducing costs. Due to its simple structure and small size, the permanent magnet DC motor is often used in small toys, fans, CD drives, etc., providing basic power support for these devices.
Brushed DC Motor: Brushed DC motors have two key components: brushes and a commutator. The brushes and commutator work together to periodically change the direction of the current in the armature winding during motor operation, ensuring continuous rotation of the motor. Its simple structure and low cost make it widely used in places where precision is not highly required, such as power tools, electric bicycles, etc. However, the brushes will wear out over time due to friction with the commutator, requiring regular maintenance and replacement.
Brushless DC Motor (BLDC): The brushless DC motor eliminates the traditional brushes and commutator, using an electronic commutator to control the energizing sequence of the motor winding. This design reduces mechanical wear, increases efficiency and lifespan, and lowers maintenance costs. Thanks to its high efficiency and long lifespan, the brushless DC motor is widely used in many fields, such as drones, robots, electric vehicles, and computer cooling fans, providing efficient and stable power for these devices.
AC motors operate based on the principle of electromagnetic induction. When AC current passes through the stator winding, a rotating magnetic field is generated inside the motor. This rotating magnetic field cuts the rotor conductors, inducing electromotive force and thus generating current in the rotor conductors. The current-carrying rotor conductors experience an electromagnetic force in the rotating magnetic field, causing the rotor to rotate along with the rotating magnetic field. The speed of an AC motor is related to the power frequency and the number of poles of the motor, with the synchronous speed formula being n = 60f / p, where n is the synchronous speed, f is the power frequency, and p is the number of poles of the motor.
Induction Motor (Asynchronous Motor)
Squirrel Cage Induction Motor: The structure of the squirrel cage induction motor is extremely simple, cost-effective, and highly reliable, occupying a large share of the industrial motor field. Its rotor resembles a squirrel cage, composed of a series of short-circuited bars. When the stator winding passes through AC current to create a rotating magnetic field, the rotor bars cut the lines of magnetic force, generating induced current and thus electromagnetic torque, causing the rotor to rotate. Due to its simple structure and reliable operation, the squirrel cage induction motor is widely used in various industrial equipment such as pumps, fans, compressors, and machine tools.
Wound Rotor Induction Motor: The rotor winding of the wound rotor induction motor is brought out through slip rings and brushes, allowing for the external connection of resistors. By adjusting the size of the external resistance, the rotor current and power factor of the motor can be changed, enabling speed control and adjustment of the starting torque. Therefore, the wound rotor induction motor is often used in applications requiring large starting torque, such as cranes and hoists.
Synchronous Motor
Permanent Magnet Synchronous Motor (PMSM): The rotor of a permanent magnet synchronous motor uses permanent magnets. When the stator winding passes through three-phase AC current, a rotating magnetic field is generated, causing the rotor to rotate synchronously with the magnetic field. Due to the presence of permanent magnets, the permanent magnet synchronous motor has high efficiency and a good power factor, allowing it to efficiently operate while providing good power factor support to the system. It is commonly used in high-precision, high-performance speed control systems such as electric vehicle drives and servo systems, providing strong power for applications with high motor performance requirements.
Electrically Excited Synchronous Motor: The rotor of the electrically excited synchronous motor is an electromagnet excited by an external DC power supply. This design allows the motor to operate stably in high-power, high-voltage applications, such as generators in thermal power plants. By adjusting the size of the excitation current, the output characteristics of the motor can be flexibly controlled to meet the needs of different operating conditions.
A stepper motor is an open-loop control motor that converts electrical pulse signals into angular or linear displacement. Its working principle is based on the action of an electromagnet. For each input pulse signal, the motor rotates one step (step angle) of a fixed angle. By precisely controlling the number and frequency of pulses, the position and speed of the motor can be precisely controlled. For example, if the step angle is 1.8°, then inputting 200 pulses will cause the motor to rotate 360°.
Variable Reluctance Stepper Motor: The variable reluctance stepper motor has a simple structure and low cost but has lower torque and precision. It is usually suitable for applications where high precision is not required, such as printers and plotters. In these devices, the variable reluctance stepper motor can meet basic positioning and movement needs.
Permanent Magnet Stepper Motor: The permanent magnet stepper motor uses permanent magnets to generate torque and has a larger step angle and torque. It is commonly used in computer peripherals, instruments, and other equipment, providing stable power output to meet certain motor performance requirements.
Hybrid Stepper Motor: The hybrid stepper motor combines the advantages of variable reluctance and permanent magnet stepper motors, offering higher resolution and torque. It is widely used in applications requiring high precision, such as CNC machine tools, automated equipment, and 3D printers, providing precise positioning and motion control to ensure high-precision operation.
A servo motor is a closed-loop control motor that can precisely control position, speed, and torque. It usually consists of a motor, encoder, and controller. The encoder provides real-time feedback on the motor's position, and the controller compares the control signal received with the actual position information fed back by the encoder. Based on the deviation between the two, the driving signal of the motor is adjusted to achieve precise control of the motor's position and speed. This closed-loop control method allows the servo motor to quickly respond to external commands and maintain high precision during operation.
DC Servo Motor: The DC servo motor has good speed regulation performance and can achieve smooth speed regulation over a wide range. However, the presence of brushes means higher maintenance costs. In the early days, DC servo motors were used in some high-precision applications such as early CNC machine tools. But with the development of technology, the maintenance issues caused by brushes have gradually limited its application range.
AC Servo Motor: The AC servo motor uses a brushless design, overcoming the wear problems of DC servo motor brushes, and offers the advantages of high precision, fast response, and high reliability. It is widely used in fields requiring high precision and dynamic performance, such as industrial automation, robotics, and CNC machine tools. It provides precise, efficient power control for devices in these fields and is an indispensable key component in modern high-end equipment manufacturing.
The linear motor breaks the traditional mode of converting rotary motor motion into linear motion through intermediate transmission mechanisms by directly converting electrical energy into linear motion. Its principle is similar to unrolling a rotary motor along its axis into a linear form, where the stator and rotor respectively generate a magnetic field and force components for linear motion. When the stator winding passes through AC current, a traveling magnetic field is generated along a linear direction, which acts on the rotor, causing the rotor to produce linear motion. This direct drive method avoids the mechanical losses and precision losses brought by traditional transmission mechanisms (such as lead screws and gears) and achieves higher speed and precision.
Flat Type Linear Motor: The flat type linear motor has a simple structure, with the stator and mover being flat. It is suitable for high-precision, high-speed short-stroke linear motion. In fields like semiconductor manufacturing equipment and high-speed machining centers, the flat type linear motor can meet the requirements for high precision and high speed, providing precise linear motion control for the production process.
U-Channel Linear Motor: The U-channel linear motor offers larger thrust and longer travel. Its structural features allow it to excel in applications requiring large thrust and long travel, such as logistics conveyor systems and automated production lines. In these application scenarios, the U-channel linear motor can efficiently achieve material conveyance and linear motion control of equipment.
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