Definition of the two
Frequency converter is a power control device that converts the power frequency power supply into another frequency by the on-off action of power semiconductor devices. It can realize the soft start of AC induction motor, frequency control, improve the running accuracy, change the power factor and other functions. The frequency converter can drive the frequency conversion motor and the ordinary AC motor, which mainly plays the role of regulating the motor speed. The frequency converter is usually composed of rectifier unit, intermediate circuit, inverter and controller.
Servo system is an automatic control system that makes the object’s position, azimuth, state and other output controlled quantity can follow the input target (or given value) arbitrary change. The main task is to amplify, transform and regulate the power according to the requirements of the control command, so that the torque, speed and position control of the output of the driving device is very flexible and convenient.
The common features of both
The technology of AC servo itself is to learn from and apply the technology of frequency conversion. On the basis of the servo control of DC motor, it is realized by imitating the control mode of DC motor through the PWM mode of frequency conversion. In other words, the AC servo motor must have the link of frequency conversion: Frequency conversion is the power frequency of 50, 60Hz AC first rectifier into DC, and then through the control gate of all kinds of transistors (IGBT, IGCT, etc.) through the carrier frequency and PWM regulation inverter frequency adjustable waveform similar to sine and cosine pulsation electricity, because of the adjustable frequency, so the speed of the AC motor can be adjusted (n=60f/p, n speed, f frequency, p pole logarithm).
application
Because of the differences in performance and function between frequency converter and servo, the applications are not the same:
1. In the occasions of speed control and torque control, the requirements are not very high. There are also position feedback signals in the upper part of the closed-loop position control by frequency conversion, with low accuracy and response. Now some frequency conversion also accept pulse train signal to control the speed, but it does not seem to be able to directly control the position.
2, in the case of strict position control requirements can only be realized with servo, and the servo response speed is far greater than frequency conversion, some of the precision and response of the degree of high requirements of the occasion also use servo control, can use frequency conversion control of the movement of the occasion almost can be replaced by servo, the key is two points: one is the price servo is far higher than frequency conversion, the second is the power of the reason: The maximum frequency conversion can do hundreds of KW, or even higher, and the maximum servo is dozens of KW. But with the continuous improvement of servo motor technology, the power can gradually reach hundreds of KW.
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