The term servo motor comes from the Latin word "servus" – "servant". This is because servo motors were originally designed as simple auxiliary drives for use in machine tools. Today, a servo motor is generally understood as being mostly an electric motor that has a control mechanism and can provide feedback on its rotational or linear position.
Servo motors are characterised by:
Servo motors can be operated with electronic position, torque or speed control. Sometimes they are also operated in a combination of different types of control mechanisms. They can be divided into two basic types – synchronous and asynchronous servo motors. The fundamental difference between synchronous and asynchronous servo motors lies in their operating mode and design.
A synchronous servo motor generates a magnetic rotating field that rotates exactly synchronously with the frequency of the applied voltage or current. The speed of the motor is thus directly proportional to the frequency of the applied voltage or current. Synchronous motors are typically used when high precision and speed are required.
An asynchronous servo motor, on the other hand, works differently. In an asynchronous servo motor, the magnetic field is generated by passing current through the rotor. The rotation of the rotor is caused by the interaction between the rotating magnetic field and the conductors in the rotor. The speed of an asynchronous servo motor depends on the load it is driving and is generally lower than that of a synchronous servo motor. Asynchronous servo motors are typically used for applications with higher torque.
So whether a synchronous or an asynchronous servo motor is better suited for the application always depends on the specific requirements.
Permanently excited synchronous servo motors, asynchronous motors and brushed DC motors are widely used as servo motors. AC servo motors are usually motors that are operated using supply voltages that are generated directly by rectifying an alternating voltage. In contrast, servo motors that can be operated directly using an extra-low voltage are called DC servo motors. However, this classification doesn't say anything about the motor type. According to this definition, permanently excited synchronous motors are used both as AC and DC synchronous motors. Asynchronous motors and reluctance motors are mainly used as AC servo motors; permanently or externally excited, brushed DC motors are used more as DC servo motors.
With increasing automation in all areas of machine and plant construction comes the need for ever shorter cycle times and greater flexibility when changing products. This development has led to the servo drives used today. These motors are mainly used for applications in the following industries:
Servo motors are particularly valued in these industries because their performance and application can be scaled. They always offer the right performance, whether as a direct drive for high-precision axes or as a cost-effective motor-gear unit combination. In addition, the effort and time needed to cable and install servo motors is low, as they can be used with digital signal transmission and combined cables.