Servo drivers and motors
The inverter is a power control device that transforms the industrial frequency power supply into another frequency by using the on-off effect of the power semiconductor device, which can realize the functions of soft start-up, variable frequency speed control, improving operation accuracy and changing power factors. The drive converter drives the variable frequency motor, the ordinary AC motor, mainly acts as the role of regulating the speed of the motor. The drive is usually composed of a rectifier unit, a high capacity capacitor, an inverter, and a controller. The following Shenzhen Vikoda servo motor to talk about the differences and commonality between servo drivers and inverters.
How both work
The speed control principle of the inverter is mainly subject to the four factors of asynchronous motor speed n, asynchronous motor frequency f, motor differential rate s, motor adji p. The speed n is directly related to the frequency f, as long as the frequency f can change the speed of the motor, when the frequency f changes in the range of 0-50Hz, the motor speed adjustment range is very wide.
Variable frequency regulation is achieved by changing the motor power supply frequency to achieve speed regulation. Mainly using the cross--straight-to-cross mode, the frequency AC power supply is converted into a DC power supply through a rectifier, and then the DC power supply is converted into a frequency, voltage can be controlled AC power supply to supply the motor. The circuit of the drive is generally composed of four parts: rectifier, intermediate DC link, inverter and control. The rectifier part is a three-phase bridge uncontrollable rectifier, the inverter part is an IGBT three-phase bridge inverter, and the output is PWM waveform, and the intermediate DC link is filtering, DC energy storage and buffer reactive power.
The servo system simply works by giving the speed and position signals back to the driver via rotary encoders, rotary transformers, etc. on the basis of an open-loop controlled AC-DC motor. Coupled with the current closed loop inside the driver, the accuracy and time response characteristics of the motor's output to the set value are improved by these three closed-loop adjustments. Servo system is a dynamic follow-up system, and the steady-state balance achieved is also dynamic balance.
First, common
AC servo technology itself is to learn from and apply the technology of frequency inverter, on the basis of the servo control of DC motor through the PWM mode of frequency change to imitate the control mode of DC motor to achieve, Wykoda servo motor manufacturers, that is to say, AC servo motor must have the link of frequency change: frequency inverter is the frequency of 50, 60HZ AC first rectition into DC Electricity, and then through various types of transistors (IGBT, IGCT, etc.) that can control the gate pole, the pulsed electricity similar to the sine chord is adjusted by the carrier frequency and PWM to adjust the inverse waveform to the frequency, so the speed of the AC motor can be adjusted (n-60f/p, n-speed, f-frequency, p-pair).
Second, different points
1. Different overload capabilities. Servo drivers typically have 3x overload capacity and can be used to overcome inertial loads at the moment of start-up, while drives typically allow 1.5x overload.
2. Control accuracy. The control accuracy of the servo system is much higher than that of the variable frequency, and the control accuracy of the servo motor is usually guaranteed by the rotary encoder at the rear end of the motor shaft. Some servo systems have a control accuracy of 1:1000.
3. Different applications. Variable frequency control and servo control are two categories of control. The former belongs to the field of transmission control, while the latter belongs to the field of motion control. One is to meet the general requirements of industrial applications, performance indicators are not high requirements of the application, the pursuit of low-cost. The other is the pursuit of high precision, high performance, high response.
4. Wykoda servo motor, with different acceleration and deceleration properties, is processed from a stationary state to 2000r/min in an empty capacity and will not take more than 20ms. The acceleration time of the motor is related to the inertia and load of the motor shaft. Usually the greater the inertia, the longer the acceleration time.
The above is focused on domestic motion controllers, servo drives, servo motors and other automation equipment 16 years of manufacturers of Wykoda Technology detailed description, want to learn more professional information or product supply and demand, welcome to pay attention to us, all products in stock supply.
An important difference between servo and frequency inverter is that the inverter can be codeless, and the servo must have an encoder for electronic exchange.
First, the two have in common: AC servo technology itself is to learn from and apply the technology of variable frequency, on the basis of the servo control of DC motor through the frequency of PWM mode to imitate the control mode of DC motor to achieve, that is to say, AC servo motor must have the link of frequency change: frequency inverter is the frequency of 50, 60HZ AC first rective into DIRECT current, and then through various transistors (IGBT, IGCT, etc.) that control the gate poles, adjust the inversely adjustable waveform to the frequency adjustable waveform similar to the pulsation of the sine chord, and because the frequency is adjustable, the ac motor speed can be adjusted (n-60f/p, n-speed, f-frequency, p-polar number)
Second, talk about inverters: simple inverters can only adjust the speed of the AC motor, then can open or close the loop depending on the control mode and the drive, this is the traditional sense of V/F control. Many inverters have been established by mathematical models to convert the UVW3 phase of the ac motor's seth magnetic field into a part of two currents that can control the motor's speed and torque, and most of the well-known brands that can control torque are using this method to control torque. The output of UVW per phase should be added to the current detection device of the Hall effect, the PID regulation of the current ring that forms the closed-loop negative feedback after sampling feedback, and the variable frequency of ABB proposes the direct torque control technology which is different from this way, please refer to the relevant information. This can not only control the speed of the motor can also control the torque of the motor, and the speed control accuracy is better than v/f control, encoder feedback can also be added without, plus time control accuracy and response characteristics are much better.
Third, talk about servo: driver aspects: servo drive in the development of frequency conversion technology, under the premise of the current ring inside the driver, speed ring and position ring (the drive does not have this ring) have carried out more accurate control technology and algorithmic operation than the general frequency conversion, in terms of function is also much more powerful than traditional servo, the main point can be accurate location control. Speed and position are controlled by the pulse sequence sent by the upper controller (although some servos integrate control units internally or set parameters such as position and speed directly in the drive through bus communication), and algorithms and faster and more accurate calculations and better performance electronics inside the drive make it superior to the drive. Motor aspects: servo motor materials, structure and processing process is much higher than the drive of the ac motor (general AC motor or constant torque, constant power and other types of variable frequency motor), that is, when the driver output current, voltage, frequency changes quickly power supply, servo motor can respond to changes in the power supply action changes, response characteristics and anti-overload capacity is much higher than the frequency drive AC motor, the serious difference in motor performance is also the fundamental difference between the two. That is to say, the inverter output can not change so fast power signal, but the motor itself can not react, so in the inverter's internal algorithm set in order to protect the motor made the corresponding overload settings. Of course, even if the output capacity of the drive is limited without setting it, some high-performance driveers can be driven directly.
