1 brushless DC motor
Brushless DC motor (BLDCM) is developed based on a brushless DC motor on, but its current drive is hundred-percent AC; brushless DC motor can be divided into brushless speed motor and brushless torque motor. Generally, brushless motor drive current has two kinds, one is trapezoidal wave (usually square wave), and the other is sine wave. Sometimes, the former is called brushless DC motor, and the latter is called AC servo motor, which is a kind of AC servo motor.
In order to reduce the inertia, the brushless DC motor usually adopts the "slender" structure. Brushless DC motor is much smaller in weight and volume than brush DC motor, and the corresponding moment of inertia can be reduced by about 40% - 50%. Due to the processing of permanent magnet material, the general capacity of Brushless DC motor is less than 100kW.
This motor mechanical characteristic and regulation characteristics of good linearity, wide speed range, long service life, convenient maintenance and low noise, does not exist a series of problems caused by the brush, so the motor has great potential applications in the control system.
2 step motor
The stepping motor is a kind of electrical pulses into angular displacement of the actuator; the more popular point of view: when the stepper driver receives a pulse signal, it drives stepper motor to set the direction of rotation of a fixed angle. The angular displacement we can control the number of the motor is controlled by pulse, so as to achieve the purpose of accurate positioning; at the same time also can control the pulse frequency to control the motor rotation speed and acceleration, so as to achieve the purpose of speed. At present, the most commonly used stepping motors include reactive stepping motor (VR), permanent magnet stepping motor (PM), hybrid stepping motor (HB) and single-phase stepping motor, etc..
The difference between stepper motor and ordinary motor is mainly in the form of pulse drive, it is this characteristic, stepper motor can be combined with modern digital control technology. But stepping motor in the control accuracy, speed change range, low speed performance is not as good as the traditional closed-loop control of DC servo motor; therefore, the main application in the precision requirements are not particularly high occasions. Due to the characteristics of stepping motor has the advantages of simple structure, high reliability and low cost, so the stepper motor is widely used in various fields of production practice; especially in the manufacture of CNC machine tools, the stepper motor A/D does not need the conversion, can direct digital Mai Chongxin into angular displacement, it has been regarded as CNC machine tool the most ideal actuator.
In addition to the application of CNC machine tools, stepper motor can also be used on other machines, such as automatic feeding machine motor, motor as universal floppy drive, can also be used in printers and plotters.
In addition, the stepper motor has many defects; because the stepper motor has no-load starting frequency, so the low-speed stepper motor can operate normally, but if higher than a certain speed will not start, and accompanied by a sharp whistle; different subdivision drive accuracy may vary greatly, the fine fraction is more difficult to control precision; also, the stepping motor rotates at low speed with greater vibration and noise.
3 servo motor
Servo motor is widely used in a variety of control systems, the input voltage signal can be converted to mechanical output on the motor shaft, dragging the control element, so as to achieve the purpose of control.
Servo motor has DC and AC; the first servo motor is a general DC motor, in the case of low control accuracy, only the general DC motor is used as servo motor. At present, the DC servo motor is a small power DC motor from its structure. The armature control and magnetic field control are adopted in the excitation, but armature control is usually adopted.
The classification of rotary motor, DC servo motor can well meet the requirements of the control system for the mechanical properties, but due to the commutator exist many deficiencies: between the commutator and brushes is easy to produce sparks, interference drive to work, can not be used in flammable gas occasions; brush and commutator friction, will produce large the dead; complicated structure, difficult maintenance.
AC servo motor is essentially a two-phase asynchronous motor, and there are three main control methods: amplitude control, phase control and amplitude phase control.
In general, the servo motor to control the motor speed required by the voltage signal; the speed can change with the voltage signal and the continuous change of the motor; reflects the faster, smaller and smaller power control. Servo motor is mainly used in all kinds of motion control system, especially servo system.
4 torque motor
The so-called torque motor is a kind of flat multipole permanent magnet DC motor. The armature has more slots, the number of commutator slices and the number of series conductors, so as to reduce torque ripple and speed ripple. There are two kinds of torque motor: DC torque motor and AC torque motor.
The self inductance reactance DC torque motor is very small, so a very good response; its output torque and the input current is proportional to the independent of the rotor speed and position; it can in the near stall under direct and low-speed running without load connection gear, so the load on the shaft can high torque the ratio of inertia, and can eliminate the system error caused by using the reduction gear.
AC torque motor can be divided into two kinds of synchronous and asynchronous. At present, the squirrel cage asynchronous torque motor is commonly used. It has the characteristics of low speed and strong torque. In general, AC torque motor used in the textile industry, its working principle and structure of single-phase asynchronous motor and the same, but the resistance of squirrel cage rotor is larger, so the soft mechanical properties.