Types of DC servo motors

The editor has previously introduced the classification of servo motor encoders. It can be seen that the classification of encoders is different from that of servo motors. There are many types of DC motors in servo motors, and each type of DC motor has been widely used. Next, I will introduce the types of DC servo motors. I hope it can help everyone!

A servo system that uses a DC motor as a driving element is called a DC servo system. Because DC servo motors are relatively simple to adjust speed, especially separately excited and hydromagnetic DC motors, which have relatively hard mechanical properties, DC motors have been widely used in CNC machine tools since the 1970s.

There are many types of DC servo motors. With the development of science and technology, new types and new structures are still emerging.

According to the method of generating magnetic field, DC motors can be divided into five types: separately excited, permanent magnet, parallel excited, series excited and compound excited.

The permanent magnet type uses soft magnetic materials such as oxide, aluminum-nickel cobalt, and earth cobalt to establish an exciting magnetic field. Structurally, DC servo motors are general armature type, slotless armature type, printed armature type, coiled disc type and coreless cup armature type. To prevent brush commutator contact, there are also brushless DC servo motors.

According to the control method, DC servo motors can be divided into magnetic field control method and armature control method. Obviously, permanent magnet DC servo motors can only use armature control, and general electromagnetic DC servo motors also use armature control.

In CNC machine tools, the commonly used DC servo motors in the feed system mainly include the following types:

(1) Small inertia DC motor

Small inertia DC servo is named after its small moment of inertia. This type of motor is generally a permanent magnet type, and the armature windings include slotless armature type, printed armature type and coreless cup armature type. Because the small-inertia DC motor minimizes the rotational inertia of the armature, it can achieve fast response speed. In early CNC machine tools, this type of motor was widely used. Small inertia servo motors are still used in CNC machine tools in some countries, such as France.

(2) DC torque motor

Also known as large inertia wide-adjustable DC servo motor. On the one hand, because its rotor diameter is larger. The number of turns of the coil winding is increased, the torque is large, and the moment of inertia is larger than other types of motors. It can also work for a long time under large overload torque, so it can be directly connected to the screw without the need for central transmission equipment. On the other hand, because it has no excitation circuit losses, its dimensions are smaller than similar other Yufeng servo motors. It also has an outstanding feature, which is that it can achieve dry and stable operation at a lower speed, and the speed can reach 1r/min or even 0.1r/min. Therefore, this kind of motor is widely used in CNC machine tools.

(3) Drama-free DC motor

This kind of servo is also called a commutator-less motor. It has no directional control device and consists of a synchronous motor and an inverter. The inverter is controlled by a rotor position sensor mounted on the rotor. It is essentially an AC tuned motor. Because its speed regulation performance can reach the level of DC servo generators, and the commutation equipment and brush components are eliminated, the service life of the motor is greatly extended.