What are the five major categories of DC servo motors?
Publish Time: 2024-08-22
What are the five major categories of servo motors:According to the way the magnetic field is generated, DC motors can be divided into five types: externally excited, permanent magnet, parallel excited, series excited and compound excited. Permanent magnet uses soft magnetic materials such as oxide, aluminum nickel cobalt, rare earth bismuth to establish the excitation magnetic field.In terms of structure, DC servo motors are general armature type, slotless armature type, printed armature type, winding disk type and hollow cup armature type. In order to avoid contact with the brush commutator, 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. Water magnetic DC servo motors can only use armature control method, and most general electric DC servo motors also use armature control method.In CNC machine tools, the DC servo motors commonly used in the feed system are mainly the following:(1) Small inertia DC servo motorThe small inertia DC servo motor is named because of its small rotation inertia. This type of motor is generally a water-magnetic type, and the armature winding has three types: phaseless armature type, printed armature type, and hollow cup armature type. Because the small inertia DC motor minimizes the rotational inertia of the armature, it can achieve the fastest response speed. In early CNC machine tools, this type of servo motor is widely used. Small-scale servo motors are still used in CNC machine tools in some countries, such as France.(2) DC torque motorAlso known as large inertia wide speed regulation DC servo motor. On the one hand, due to its larger rotor diameter, the number of coil winding turns increases, the torque is large, and the rotation speed is larger than other types of motors. And it can work for a long time under large overload torque. Therefore, it can be directly connected to the screw without the need for an intermediate transmission device. On the other hand, because it has no loss in the excitation circuit, its external dimensions are smaller than other similar DC servo motors. It also has a prominent feature that it can achieve stable operation at a lower speed, and the minimum speed can reach 1r/min, or even 0.1r/min. Therefore, this servo motor has been widely used in CNC machine tools.(3) Brushless DC servo motorThis type of servo motor is also called a commutatorless motor. It has no commutator. It 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 speed-regulating motor. Its speed regulation performance can reach the level of a DC servo generator. The commutation device and brush components are eliminated, which greatly improves the service life of the motor.Classification of DC servo motors_Structure of DC servo motorsStructure of DC servo motors1. The rotor, also known as the armature, is made of laminated silicon steel sheets with coils embedded on the surface. When DC power is applied, it generates an electromagnetic torque that drives the load to rotate under the action of the stator magnetic field.2. Brushes and commutator segments. In order to keep the generated electromagnetic torque in a constant direction and enable the rotor to rotate uniformly and continuously in a fixed direction, the brushes are connected to an external DC power supply and the commutator segments are connected to the armature conductor.3. Stator. The stator magnetic pole magnetic field is generated by the stator magnetic poles. According to the way the magnetic field is generated, DC servo motors can be divided into permanent magnet type and externally excited type. The permanent magnet poles are made of permanent magnet materials, and the separately excited poles are made of laminated stamped silicon steel sheets. A constant magnetic field is generated when a DC current is passed through the outer winding coil.
