The fundamental concept of servo systems revolves around precision, accuracy, and rapid positioning. Variable Frequency Drives (VFDs) play an indispensable role in servo control as an internal component, essential for achieving continuous speed control. However, the control of servo systems involves significantly different aspects such as current loops, velocity loops, or position loops. Furthermore, servo motors differ in structure from ordinary motors, designed to meet the requirements of rapid response and precise positioning.

AC Servo Technology:

AC servo technology inherently involves the application of frequency modulation. It is an extension of DC motor servo control, implemented through Pulse Width Modulation (PWM) by emulating the control approach of DC motors. This signifies that AC servo motors must incorporate a frequency modulation section. The process involves rectifying AC power into DC power, followed by modulation into a frequency-adjustable waveform using various transistors (e.g., IGBTs, IGCTs). This process is akin to generating a sinusoidal pulsating current.

Variable Frequency Drives (VFDs):

A basic VFD primarily regulates the speed of an AC motor. Depending on the control method and the VFD, it can operate in an open-loop or closed-loop configuration. Many modern VFDs establish mathematical models, transforming the stator magnetic field (UVW3) of AC motors into two current components. This enables the control of both motor speed and torque. Renowned brands predominantly use this method for torque control. Each phase of UVW output requires Hall effect current detection devices, leading to a closed-loop negative feedback current loop adjusted by PID. ABB’s VFD has proposed a torque control technology different from this model, providing improved speed control precision. Encoder feedback can be incorporated for enhanced control precision and response characteristics.

Servo Drive

Servo Drives:

Servo drives excel in precision and functionality compared to conventional VFDs. The control loops for current, velocity, and position in servo drives undergo more accurate technical and algorithmic computations than general-purpose VFDs. A key feature is the ability to achieve precise position control. Velocity and position are controlled through pulse sequences sent by an upper-level controller. Some servo systems integrate control units internally or directly set parameters such as position and speed through bus communication. The algorithms within the drive, faster and more accurate calculations, and superior electronic components make servo drives superior to VFDs.

Servo Motors:

Servo motors exhibit superior materials, structure, and manufacturing processes compared to VFD-driven AC motors. When a drive outputs rapidly changing power signals, servo motors can dynamically respond to changes in the power supply. Their response characteristics and overload resistance far surpass those of AC motors driven by VFDs. Even without VFD settings, the output capacity of servo motors is limited. Some high-performance VFDs can directly drive servo motors.

AC Motors:

AC motors are generally categorized as synchronous or asynchronous. Synchronous AC motors have rotors made of permanent magnet materials, rotating at the same speed as the stator, hence the term “synchronous.” Asynchronous AC motors, on the other hand, consist of rotors with induction coils. The speed of the rotor is always slightly less than that of the stator, and this difference is known as slip. Correspondingly, there are synchronous and asynchronous VFDs for AC motors, and servo motors also come in synchronous and asynchronous varieties.

Applications:

Due to differences in performance and functionality, VFDs and servo drives find application in distinct scenarios:

VFDs are generally employed when speed and torque control requirements are not extremely high. While some VFDs now accept pulse sequence signals for speed control, they may not directly control position.

Servo drives are used in applications that demand strict position control. Their response speed is significantly higher than that of VFDs. Servo control is adopted in almost all motion control scenarios where VFDs can be replaced by servos. Two key considerations are the higher cost of servos compared to VFDs and the power factor: the maximum power of VFDs can reach several hundred kilowatts or even higher, while the maximum power of servos is in the range of several dozen kilowatts.

The choice between VFDs and servo drives depends on the specific application requirements and the balance between cost and performance.

Note: The translation may be refined further based on specific nuances or preferences.

More: Detailed Explanation Of The Function And Parameters Of The Servo Drive

The fundamental concept of servo systems revolves around precision, accuracy, and rapid positioning. Variable Frequency Drives (VFDs) play an indispensable role in servo control as an internal component, essential for achieving continuous speed control. However, the control of servo systems involves significantly different aspects such as current loops, velocity loops, or position loops. Furthermore, servo motors differ in structure from ordinary motors, designed to meet the requirements of rapid response and precise positioning.

AC Servo Technology:

AC servo technology inherently involves the application of frequency modulation. It is an extension of DC motor servo control, implemented through Pulse Width Modulation (PWM) by emulating the control approach of DC motors. This signifies that AC servo motors must incorporate a frequency modulation section. The process involves rectifying AC power into DC power, followed by modulation into a frequency-adjustable waveform using various transistors (e.g., IGBTs, IGCTs). This process is akin to generating a sinusoidal pulsating current.

Variable Frequency Drives (VFDs):

A basic VFD primarily regulates the speed of an AC motor. Depending on the control method and the VFD, it can operate in an open-loop or closed-loop configuration. Many modern VFDs establish mathematical models, transforming the stator magnetic field (UVW3) of AC motors into two current components. This enables the control of both motor speed and torque. Renowned brands predominantly use this method for torque control. Each phase of UVW output requires Hall effect current detection devices, leading to a closed-loop negative feedback current loop adjusted by PID. ABB’s VFD has proposed a torque control technology different from this model, providing improved speed control precision. Encoder feedback can be incorporated for enhanced control precision and response characteristics.

Servo Drive

Servo Drives:

Servo drives excel in precision and functionality compared to conventional VFDs. The control loops for current, velocity, and position in servo drives undergo more accurate technical and algorithmic computations than general-purpose VFDs. A key feature is the ability to achieve precise position control. Velocity and position are controlled through pulse sequences sent by an upper-level controller. Some servo systems integrate control units internally or directly set parameters such as position and speed through bus communication. The algorithms within the drive, faster and more accurate calculations, and superior electronic components make servo drives superior to VFDs.

Servo Motors:

Servo motors exhibit superior materials, structure, and manufacturing processes compared to VFD-driven AC motors. When a drive outputs rapidly changing power signals, servo motors can dynamically respond to changes in the power supply. Their response characteristics and overload resistance far surpass those of AC motors driven by VFDs. Even without VFD settings, the output capacity of servo motors is limited. Some high-performance VFDs can directly drive servo motors.

AC Motors:

AC motors are generally categorized as synchronous or asynchronous. Synchronous AC motors have rotors made of permanent magnet materials, rotating at the same speed as the stator, hence the term “synchronous.” Asynchronous AC motors, on the other hand, consist of rotors with induction coils. The speed of the rotor is always slightly less than that of the stator, and this difference is known as slip. Correspondingly, there are synchronous and asynchronous VFDs for AC motors, and servo motors also come in synchronous and asynchronous varieties.

Applications:

Due to differences in performance and functionality, VFDs and servo drives find application in distinct scenarios:

VFDs are generally employed when speed and torque control requirements are not extremely high. While some VFDs now accept pulse sequence signals for speed control, they may not directly control position.

Servo drives are used in applications that demand strict position control. Their response speed is significantly higher than that of VFDs. Servo control is adopted in almost all motion control scenarios where VFDs can be replaced by servos. Two key considerations are the higher cost of servos compared to VFDs and the power factor: the maximum power of VFDs can reach several hundred kilowatts or even higher, while the maximum power of servos is in the range of several dozen kilowatts.

The choice between VFDs and servo drives depends on the specific application requirements and the balance between cost and performance.

Note: The translation may be refined further based on specific nuances or preferences.

More: Detailed Explanation Of The Function And Parameters Of The Servo Drive

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