Electric motors, also known as motors, are found in many devices, such as air pumps for fish enthusiasts. To enhance your understanding of electric motors, this article will introduce asynchronous motors, torque motors, and the differences between them. If you are interested in electric motors, please continue reading.
I. Asynchronous Motor
An asynchronous motor, also known as an induction motor, is an AC motor that converts electromechanical energy into mechanical energy by generating electromagnetic torque through the interaction between the rotating magnetic field in the air gap and the induced current in the rotor windings.
Three-phase asynchronous motors are mainly used as electric motors to drive various production machinery, such as fans, pumps, compressors, machine tools, light industrial and mining machinery, threshers and crushers in agricultural production, and processing machinery for agricultural and sideline products. They are simple in structure, easy to manufacture, inexpensive, reliable in operation, robust and durable, have high operating efficiency, and suitable working characteristics.
The asynchronous motor was invented in 1885 by Italian physicist and electrical engineer Ferraris. In 1888, he published an experimental report providing a rigorous scientific description of the rotating magnetic field, laying the foundation for the later development of asynchronous motors and self-starting motors. Ferraris believed that the scientific value of his rotating magnetic field theory and his new products far exceeded their material value; therefore, he intentionally did not apply for patents for his inventions, but instead demonstrated these latest achievements to the public in his 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. A year later, Mikhail Dolivo-Dobrovolsky invented the squirrel-cage asynchronous motor. The development of asynchronous motors was 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 asynchronous motor is the most widely used asynchronous motor.
II. Torque Motor
A torque motor is a type of motor that directly outputs torque. Its torque is proportional to the current, so torque and speed can be controlled by controlling the current. Torque motors are generally suitable for applications requiring precise torque and speed control, such as industrial robots, CNC machine tools, and textile machinery.
Torque motor principle: A torque motor can maintain constant torque over a wide speed range. It is suitable for transmission applications requiring constant torque with two-speed settings. For example, in dyeing and printing machinery, when fabric is transmitted through several rollers, the fabric does not wrap around the rollers but adheres to the roller surface for driving. The diameter of the rollers remains constant. In this case, a torque motor should be used to ensure constant torque and constant fabric tension at any speed.
Torque motors are designed for prolonged low-speed operation (even when stopped), but they generate significant heat and are typically cooled by external forced air cooling from a blower. When using a torque motor, ensure the blower is functioning properly. The area around the blower should be well-ventilated and free of dry, flammable materials. Avoid proximity to flammable dust or volatile oils.
Considering the varying operating conditions, mechanical windings or conveyors driven by torque motors require different materials and specifications, necessitating varying tensions. Torque regulation of torque motors or variable-speed motors within a certain range is required, typically necessitating adjustments to the voltage applied to the torque motor to meet these requirements. When the input voltage of the torque motor changes, a voltage regulator is usually employed. To improve the strength of mechanical characteristics and the accuracy of regulation, thyristor negative feedback control circuits can also be used for stepless speed regulation, but the system becomes more complex.
III. Differences between torque motors and asynchronous motors
There are several important differences between torque motors and asynchronous motors:
The working principles are different: torque motors are based on the principle of hysteresis, while asynchronous motors are based on the principle of electromagnetic induction. There is magnetic damping between the rotor and stator of a torque motor, so it can maintain a relatively stable speed and output torque when the load increases, while asynchronous motors may experience speed and torque fluctuations 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 and lower speed applications.
The difference lies in efficiency and accuracy: Torque motors typically have higher efficiency and accuracy because they can control the rotor position and speed. In contrast, the efficiency and accuracy of asynchronous motors can be affected by rotor slip.
Different control methods: Due to differences in their 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, while asynchronous motors can achieve speed regulation through simple frequency converter control.
