As we all know, servo motor refers to the engine that controls the operation of mechanical components in the servo system. It is an indirect speed change device to supplement the motor. So do you know about the low inertia and high inertia of the servo motor? Today, I will introduce the two concepts of servo motor.

Servo motor refers to the engine that controls the operation of mechanical components in the servo system. The rotor speed of the servo motor is controlled by the input signal and can respond quickly. It is used as an actuator in the automatic control system, and has the characteristics of small electromechanical time constant, high linearity, starting voltage, etc. it can convert the received electrical signal into the angular displacement or angular speed output on the motor shaft.

## Moment of inertia = radius of rotation * mass

Low inertia means that the motor is relatively flat and long, and the inertia of the main shaft is small. When the motor makes repeated movements with high frequency, the inertia is small, and the heating is small. Therefore, low inertia motor is suitable for high-frequency reciprocating motion. But the general torque is relatively small.

The servo motor with high inertia is relatively bulky and has large torque. It is suitable for occasions with large torque but not very fast reciprocating motion. Because the high-speed movement stops, the driver needs to generate a large reverse driving voltage to stop this large inertia, and the heating is very large.

Inertia is a measure of the inertia of a rigid body rotating around an axis. Rotational inertia is a physical quantity that represents the magnitude of the rotational inertia of a rigid body. It is related to the mass of the rigid body and the dispersion of the mass relative to the axis of rotation. (rigid body refers to the object without any change in the ideal state). The moment of inertia of the motor encountered at the selected time is also an important indicator of the servo motor. It refers to the inertia of the servo motor rotor itself, which is important for the acceleration and deceleration of the motor. If the inertia can not be well matched, the motor action will be very unstable.

Generally speaking, the motor with small inertia has good braking performance, quick response to startup, acceleration and suspension, and good high-speed reciprocation. It is suitable for some occasions with light load and high-speed positioning, such as some linear high-speed positioning organizations. Medium and large inertia motors are suitable for occasions with large load and high requirements for stability, such as some circular motion organizations and some machine tool occupations.

If the load is relatively large or the acceleration characteristic is relatively large, and the motor with small inertia is selected, it may cause too much damage to the motor shaft. The selection should be based on the size of the load, the size of the acceleration, etc. the general selection manual has the relevant energy calculation formula.

The servo motor driver responds to the servo motor. The optimal value is that the ratio of load inertia to motor rotor inertia is one, and the maximum value cannot exceed five times. Through the planning of mechanical transmission device, the load can be reduced.

The ratio of inertia to motor rotor inertia is close to one or smaller. When the load inertia is really large and the mechanical planning cannot make the ratio of load inertia to motor rotor inertia less than five times, the motor with large motor rotor inertia can be used, that is, the so-called large inertia motor. Using a large inertia motor, to achieve a certain response, the capacity of the driver should be larger.

When to select low inertia for servo motor selection? When to choose high inertia?

For load inertia matching, the inertia matching of some servo motor products can reach 50 times, but the smaller the actual value, the better. This is good for accuracy and response speed.

Servo driver

In general, in order to meet the high response of the servo system, the general servo motor is the motor with small inertia. Because the larger the rated output torque of the servo motor, the larger the rotor moment of inertia is, so it is meaningless to simply discuss the size of the motor moment of inertia. What should be discussed is the ratio of the rated output torque of the servo motor to the moment of inertia of the servo motor, Or the moment of inertia of the motor with the same rated output torque.

Generally, the servo motor with small inertia is selected to meet the high dynamic response. Of course, according to the specific application environment of the servo motor, you can also select the servo motor with medium inertia and high inertia, such as the servo motor as the spindle. When the requirements for fast response are not so high, but the requirements for speed control are very precise. It is often required to run in the low-speed and low-frequency state, and it is also required to have the encoder simulation signal output. At this time, the frequency converter is not competent.