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The difference between the servo motor and the variable frequency motor
- Oct 13, 2017 -

The basic concept of servo is accurate, accurate and fast positioning. Frequency conversion is a necessary part of the servo control, the servo drive also exists in the frequency (to stepless speed regulation). But the servo loop current loop or the location of the ring are closed to control, which is a big difference. In addition, the construction of the servo motor and ordinary motor is different, to meet the rapid response and accurate positioning. Now on the market flow of AC servo motor for permanent magnet synchronous AC servo, but this motor is limited by the process, it is difficult to do a lot of power, more than a dozen KW synchronous servo prices and expensive, so in the field application allows In the case of AC asynchronous servo, then a lot of high-end drive is the drive, with encoder feedback closed-loop control. The so-called servo is to meet the accurate, accurate, fast positioning, as long as there is no need to meet the servo frequency dispute.

First, the two in common:

AC servo technology itself is the reference and application of the frequency conversion technology, DC motor servo control on the basis of frequency conversion by way of analog PWM motor control mode to achieve, that is, AC servo motor must have the frequency of this (IGBT, IGCT, etc.) through the carrier frequency and PWM adjustment inverter into a frequency adjustable waveform similar to the frequency (N = 60f / p, n speed, f frequency, p pole logarithm), the speed of the AC motor is adjustable due to the frequency adjustable

Second, talk about the inverter:

Simple frequency converter can only adjust the speed of AC motor, then you can open the ring can also be closed to the control mode and inverter depending on the way, this is the traditional sense of the V / F control. Now a lot of frequency conversion has been established through the mathematical model, the AC motor stator field UVW3 phase can be converted to control the motor speed and torque of the two current components, and now most of the torque control can be well-known brands of the inverter are In this way to control the torque, UVW output of each phase to increase the Hall effect of the current detection device, sampling feedback after the closed loop negative feedback current loop of the PID regulation; ABB frequency and put forward and this way different direct torque control technology , Please refer to the relevant information. This can not only control the speed of the motor can also control the motor torque, and speed control accuracy is better than v / f control, encoder feedback can also be added, plus time control accuracy and response characteristics much better.

Third, talk about the servo:

The drive side: the servo drive in the development of the frequency conversion technology under the premise of the drive inside the current loop, speed loop and position loop (the inverter does not have the ring) are more than the general frequency of more precise control techniques and algorithms, Also much stronger than the traditional frequency conversion, the main point can be precise position control. Through the host controller to send the pulse sequence to control the speed and location (of course, some servo internal integration of the control unit or through the bus communication directly to the location and speed parameters such as set in the drive), the drive inside the algorithm and faster More accurate calculations and better performance of electronic devices make it more superior to the inverter.

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