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ToggleWhat are 5 types of control motors?
As we all know, motor is an important part of drive and control system. With the development of modern science and technology, the focus of motor in practical application has begun to shift from simple drive to complex control; Especially the accurate control of the speed, position and torque of the motor. However, motors have different design and drive modes according to different applications.
At first glance, it seems that the type selection is very complex. Therefore, for people, the basic classification is made according to the purpose of rotating motors. Next, we will make a “population census” for the huge motor family, and gradually introduce the most representative, most commonly used and basic motor in the motor – control motor.
Control motor
The control motor is mainly used for accurate speed and position control, and is used as an “actuator” in the control system. It can be divided into servo motor, stepping motor, torque motor, switched reluctance motor, DC brushless motor, etc.
1. Servo motor
Servo motors are widely used in various control systems. They can convert the input voltage signal into the mechanical output on the motor shaft and drag the controlled components to achieve the control purpose. Generally, the servo motor requires that the speed of the motor be controlled by the applied voltage signal; The rotational speed can continuously change with the change of the applied voltage signal; The torque can be controlled by the current output by the controller; The motor shall have fast response, small volume and small control power. Servo motors are mainly used in various motion control systems, especially servo systems.
There are DC and AC servo motors. The earliest servo motor is a general DC motor. In the case of low control accuracy, the general DC motor is used as the servo motor. At present, with the rapid development of permanent magnet synchronous motor technology, most servo motors refer to AC permanent magnet synchronous servo motors or DC brushless motors.
2. Stepper motor
The so-called stepper motor is an actuator that converts electric pulse into angular displacement; More generally, when the stepper driver receives a pulse signal, it drives the stepper motor to rotate a fixed angle in the set direction. We can control the angular displacement of the motor by controlling the number of pulses to achieve the purpose of accurate positioning; At the same time, the speed and acceleration of the motor can be controlled by controlling the pulse frequency to achieve the purpose of speed regulation. At present, the commonly used stepping motors include reactive stepping motors (VR), permanent magnet stepping motors (PM), hybrid stepping motors (HB) and single-phase stepping motors.
The difference between stepper motor and ordinary motor is mainly the form of pulse drive. It is precisely this feature that stepper motor can be combined with modern digital control technology. However, the stepper motor is not as good as the traditional closed-loop control DC servo motor in terms of control accuracy, speed variation range and low speed performance;
Therefore, it is mainly used in situations where the accuracy requirement is not particularly high. Because of its simple structure, high reliability and low cost, stepping motors are widely used in various fields of production practice; Especially in the field of NC machine tool manufacturing, because the stepping motor does not need A/D conversion and can directly convert the digital pulse signal into angular displacement, it has been considered as the most ideal executive component of NC machine tool.
In addition to the application in CNC machine tools, stepping motors can also be used in other machines, such as the motors in automatic feeding machines, the motors in general floppy disk drives, and also in printers and plotters.
In addition, the stepper motor also has many defects; Because of the no-load starting frequency of the stepping motor, the stepping motor can operate normally at low speed, but it cannot be started if the speed is higher than a certain speed, accompanied by a sharp squeal; The precision of subdivision drives from different manufacturers may vary greatly, and the greater the subdivision, the more difficult it is to control the precision; Moreover, the stepper motor has large vibration and noise when it rotates at low speed.
3. Torque motor
The so-called torque motor is a flat multi-pole permanent magnet DC motor. The armature has more slots, commutation pieces and series conductors to reduce torque ripple and speed ripple. There are two kinds of torque motors: DC torque motor and AC torque motor.
Among them, the self-induced reactance of DC torque motor is very small, so its response is very good; Its output torque is proportional to the input current and independent of the speed and position of the rotor; It can directly connect with the load and operate at low speed without gear reduction under the condition of close to locked-rotor, so it can produce a high torque to inertia ratio on the load shaft and eliminate the system error caused by the use of reduction gear.
AC torque motor can be divided into synchronous and asynchronous. At present, squirrel-cage asynchronous torque motor is commonly used, which has the characteristics of low speed and large torque. Generally, AC torque motors are often used in the textile industry. Their working principle and structure are the same as single-phase asynchronous motors. However, due to the large resistance of squirrel cage rotor, its mechanical characteristics are relatively soft.
4. Switched reluctance motor
Switched reluctance motor (SRM) is a new type of speed regulation motor with extremely simple and solid structure, low cost and excellent speed regulation performance. It is a strong competitor of traditional control motor and has strong market potential. But at present, there are also problems such as torque ripple, running noise and large vibration, which need some time to optimize and improve to adapt to the actual market application.
5. Brushless DC motor
Brushless DC motor (BLDCM) is developed on the basis of brushless DC motor, but its driving current is AC to the letter; Brushless DC motor can be divided into brushless speed motor and brushless torque motor. Generally, there are two kinds of driving current of brushless motor, one is trapezoidal wave (generally “square wave”), and the other is sine wave. Sometimes the former is called DC brushless motor, and the latter is called AC servo motor, which is exactly one of AC servo motors.
In order to reduce the moment of inertia, the brushless DC motor usually adopts a “slender” structure. The brushless DC motor is much smaller in weight and volume than the brushless DC motor, and the corresponding moment of inertia can be reduced by about 40-50%. Due to the processing problem of permanent magnet materials, the general capacity of brushless DC motor is below 100kW.
This kind of motor has good linearity of mechanical characteristics and regulation characteristics, wide speed range, long service life, convenient maintenance and low noise, and does not have a series of problems caused by electric brush, so it has great application potential in control system.
Greensky Power Co., Ltd. is a professional manufacturer engaged in the research, development, production, sale of control motors.
If you are searching control motor for your project, please contact our sales team.