What Difference between ac servo driver and VFD


Simple VFD can only adjust the speed of the AC motor, then you can be open-loop control and closed-loop depending on the drive may be, this is the V / F control mode in the traditional sense.Now many have passed frequency mathematical model. The stator field UVW three-phase AC motor is converted to control the motor speed and torque of the two components of the current. Torque control can be performed most famous brands are now using this drive torque control mode. UVW Output to Jia Moer effect of each phase current detection device. PID closed loop feedback to adjust after sampling a current negative feedback loop. ABB inverter also proposed different ways and this direct torque control technology. This can not only control the speed of the motor can also control the motor torque. And speed control accuracy is better than the v / f control. Encoder feedback can also be added or not.When added. Control accuracy and response is much better

Servo driver:

 the servo drive in the development of inverter technology premise, inside the drive current loop, velocity loop and position loop (The VFD is not the loop) have carried out more precise than the general frequency control techniques and arithmetic operations in the functional is also a lot stronger than conventional servo, the main thing is precise position control.Pulse sequence sent by the host controller to control the speed and position (of course, some internal integration of the servo control unit or directly to the position and speed parameters set in the drive via the bus communication mode), drive internal algorithm and faster more accurate calculations and better performance of electronic devices make it superior to the VFD


 the material, structure and process of the servo motor is much better than the inverter-driven AC motor (AC motor or constant torque, constant power and other types of variable frequency motor), that is when the driver output current, voltage, frequency power is changing rapidly, the servo motor can react according to changes in motion in response, the response characteristics and overload resistance is much better than the inverter-driven AC motor, the motor aspect is a serious difference between the two fundamentally different properties . That is not the output frequency can not change so fast power signal, but the motor itself is not reaction, when the frequency of the internal algorithm is set to protect the motor overload to do the appropriate settings. Of course, even without setting the inverter output capacity is still limited, some of the excellent performance of the drive can directly drive servo motor!

An important difference between the servo and inverter

The VFD can work without encoder, servo must have an encoder for electronic commutation, AC servo technology itself is the draw and the application of frequency conversion technology, on the basis of servo-controlled DC motor imitate DC motor through the frequency of the PWM method control method to achieve, that is to say AC servo motor must have this part of the frequency: the frequency is the frequency of the alternating current is rectified into DC 50,60HZ the first, and then through the gate to control the types of transistors (IGBT, IGCT, etc.) by adjusting the carrier frequency and the PWM inverter frequency pulsating electrical adjustable waveform similar to the sine and cosine, since the frequency is adjustable, so adjustable speed AC motors on the (n = 60f / 2p, n speed, f frequency, p number of pole pairs).

Servo drives and drive contest

Currently, industrial applications, speed control and torque control of the situation in general is not very high frequency converter, the strict requirements of the position control can only be used in case of AC servo drive to achieve, there is the servo response speed far greater than the frequency, some of accuracy and response speed requirements of the occasion is also useful for AC servo drive control, that is, use VFD control motion of the occasion can almost replace AC servo drive

One of the supporting technology AC servo drive as a modern industrial automation and motion control, because of its high-speed control precision, wide speed range, high efficiency and dynamic characteristics, widely used in machine tools, printing equipment, packaging equipment, textile equipment, rubber and plastics new energy equipment, semiconductor, wind / solar and robotics, automated production lines and other fields.