Servo drivers are used to drive servo motors, which can be stepper motors or AC asynchronous motors. They are mainly used to achieve fast and accurate positioning, and are often used in applications where the movement is stop-and-go and high precision is required.
A frequency converter is used to convert industrial frequency AC power into a current suitable for adjusting the speed of a motor, thereby driving the motor. Some frequency converters can now also achieve servo control, meaning they can drive servo motors. However, servo drives and frequency converters are still different! Let's break down the differences between servo drives and frequency converters.
Similarities and differences
Similarities between the two:
AC servo technology itself borrows from and applies frequency conversion technology. It is based on the servo control of DC motors and uses the frequency conversion PWM method to imitate the control method of DC motors. In other words, AC servo motors must have a frequency conversion step: frequency conversion is to first rectify the 50 or 60 Hz AC power into DC power, and then invert it into frequency-adjustable waveforms similar to sine and cosine pulsed electricity through various controllable gate transistors (IGBT, IGCT, etc.) by carrier frequency and PWM adjustment. Since the frequency is adjustable, the speed of AC motor is adjustable (n=60f/p, where n is the speed, f is the frequency, and p is the number of pole pairs).
Differences between the two:
1. Different overload capabilities. Servo drives generally have a 3x overload capacity, which can be used to overcome the inertial torque of inertial loads at the moment of startup, while frequency converters generally allow 1.5x overload.
2. Control Precision. The control precision of servo systems is far higher than that of frequency converters. Typically, the control precision of a servo motor is ensured by a rotary encoder at the rear end of the motor shaft. Some servo systems even achieve a control precision of 1:1000.
3. Different application scenarios. Variable frequency control and servo control belong to two different categories of control. The former belongs to the field of transmission control, while the latter belongs to the field of motion control. One is for applications that meet general industrial requirements and do not have high performance requirements, pursuing low cost. The other pursues high precision, high performance, and high response.
4. Different acceleration and deceleration performance. Under no-load conditions, the servo motor takes no more than 20ms to accelerate from a standstill to 2000r/min. The acceleration time of the motor is related to the inertia of the motor shaft and the load. Generally, the greater the inertia, the longer the acceleration time.
