What is an asynchronous motor? What is a torque motor? What are the differences between them?

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An electric motor, or simply motor as we often call it, is found in many devices. This paper will introduce asynchronous motors, torque motors, as well as the differences between torque motors and asynchronous motors. 　I. Asynchronous Motor An asynchronous motor, also known as an induction motor, is an AC motor in which electromagnetic torque is generated by the interaction between the rotating magnetic field in the air gap and the induced current in the rotor windings, thereby enabling the conversion of mechanical and electrical energy into mechanical energy. 　　Three-phase asynchronous motors are primarily used as electric motors to drive various types of production machinery, such as fans, pumps, compressors, machine tools, light industry and mining equipment, threshers and crushers in agricultural production, as well as processing machinery for agricultural and sideline products. It has a simple structure, is easy to manufacture, inexpensive, reliable in operation, robust and durable, features relatively high operating efficiency, and possesses suitable operating characteristics. 　　The asynchronous motor was invented in 1885 by the Italian physicist and electrical engineer Ferraris. In 1888, an experimental report was published, providing a rigorous scientific description of rotating magnetic fields; this laid the foundation for the subsequent development of induction motors and self-starting motors. Ferraris believed that the value of his theory of rotating magnetic fields and the new products he developed was far greater in scientific terms than their material value; therefore, he chose not to apply for patents for his inventions, but instead demonstrated these latest achievements to the public in the laboratory. He also advocated the use of alternating current systems. In the same year, Nikola Tesla obtained a patent for the induction motor in the United States. One year later, Mikhail Dolivo-Dobrovolsky invented the cage-type induction motor. The development of asynchronous motors has been rapid. For asynchronous motors of the same size, the rated power increased from 5.5 kW in 1897 to 74.6 kW in 1976. The squirrel-cage induction motor is the most widely used type of induction motor. 　　II. Torque motors
A torque motor is a type of motor that directly outputs torque. Its torque is proportional to the current; therefore, both the torque and rotational speed can be controlled by regulating the current. Torque motors are generally suitable for applications requiring precise control of torque and rotational speed, such as industrial robots, CNC machines, textile machinery, etc. 　　Principle of torque motors: Torque motors can maintain a constant torque over a wide range of rotational speeds. Suitable for transmission applications that require a constant torque during two-speed operation. For example, in dyeing and printing machinery, when the fabric passes through several rollers, it does not wind around the rollers; instead, it adheres to the roller surfaces for driving. The diameter of the drum remains unchanged. In this case, torque motors should be used to ensure a constant torque and a constant tension in the fabric at any speed. 　　Torque motors can operate at low speeds for extended periods (or even remain stationary); they generate significant heat, so external blowers are typically used for forced air cooling. When using a torque motor, check whether the fan is operating properly. There should be good ventilation around the fan, and no dry or flammable materials are allowed. There are flammable dust or volatile oils nearby. 　　Given the differences in operating conditions, machines driven by torque motors for winding or conveying different materials and specifications require different tensions. To regulate the torque of a torque motor or variable-speed motor within a certain range, it is usually necessary to adjust the voltage applied to the torque motor in order to meet these requirements. When the input voltage of a torque motor changes, a voltage regulator is usually used. To improve the strength of mechanical properties and adjustment accuracy, a thyristor negative feedback control circuit can also be used for stepless speed control, but the system is relatively complex. 　　III. Differences between torque motors and asynchronous motors
There are several important differences between torque motors and asynchronous motors:
Different working principles: Torque motors operate based on the principle of hysteresis, while asynchronous motors operate based on the principle of electromagnetic induction. There is magnetic damping between the rotor and stator of a torque motor; therefore, when the load increases, it can maintain a relatively stable speed and output torque, whereas asynchronous motors may experience fluctuations in speed and torque when the load changes. 　　Different speed ranges: Torque motors typically have higher starting torque and a wider speed range, while asynchronous motors are generally suitable for medium- to low-power applications at lower speeds. 　　Efficiency and precision differ: Torque motors generally have higher efficiency and precision, as they can control the rotor’s position and speed. Meanwhile, the efficiency and accuracy of asynchronous motors may be affected by rotor slip. 　　Different control methods: Due to their different working principles and characteristics, torque motors and asynchronous motors require different control methods. Torque motors typically require more complex controllers and algorithms to achieve precise position and speed control, whereas asynchronous motors can have their speed adjusted using a simple frequency converter.