Wire Winding & Tying Machine,Stator Winding Machine,Winding Machine Motor,Cable Coiling Machine Kunshan Bolun Automation Equipment Co., Ltd , https://www.bolunmachinery.com
**Vector Control Principle – Introduction**
Vector control, also known as field-oriented control, is a method used to regulate the performance of three-phase AC motors by using a frequency inverter. This technique adjusts the output frequency and voltage magnitude and phase to control the motor's behavior. One of its main advantages is that it allows independent control of the motor’s magnetic field and torque, similar to how a DC motor operates. Vector control is widely applied in both AC induction motors and brushless DC motors. It was originally developed for high-performance applications, offering full-speed range operation, the ability to deliver rated torque at zero speed, and fast acceleration and deceleration.
The concept of vector control was first introduced in the late 1960s by K. Hasse from TU Darmstadt. Later, in the early 1970s, F. Blaschke from Siemens proposed the three-dimensional field-oriented control method in his doctoral thesis at the University of Braunschweig. This theory aimed to solve the challenge of controlling the torque of AC motors. The core idea of vector control is to measure and regulate the stator current vector of the asynchronous motor, and based on the principle of magnetic field orientation, control the excitation and torque currents to manage the motor’s torque effectively.
**Vector Control Principle**
At its core, vector control involves measuring and managing the stator current vector of an asynchronous motor. By decomposing this current into two components—excitation current (which generates the magnetic field) and torque current (which produces the torque)—the system can control their amplitude and phase. This approach mimics the behavior of a DC motor, allowing precise control over the motor’s performance. There are different types of vector control methods, including slip frequency-based control, sensorless vector control, and sensor-based vector control.
A key concept in vector control is coordinate transformation. The idea is to convert the three-phase AC stator current into a two-phase stationary reference frame, and then further transform it into a rotating reference frame, making it resemble DC current. This transformation enables decoupling of the magnetic flux and torque, resulting in more efficient and accurate control. As a result, the dynamic and static performance of an AC motor can be made comparable to that of a DC motor.
The slip frequency-based vector control method relies on the U/f = constant principle. It detects the actual motor speed and calculates the corresponding control frequency. Based on the desired torque, it controls the stator current vector and the phase between its components. This method helps reduce torque fluctuations during dynamic operations, improving the overall performance of the inverter. Early general-purpose inverters mainly used this type of vector control.
Sensorless vector control, on the other hand, eliminates the need for a speed sensor. Instead, it uses internal calculations within the inverter to estimate the magnetic flux and torque currents. This approach relies on the motor’s nameplate parameters and controls the stator voltage and frequency to match the desired values. While it offers flexibility, it requires accurate motor parameter input for optimal performance.
Modern general-purpose inverters now feature automatic motor parameter identification and adaptive control. These systems can identify motor parameters before operation and adjust the control algorithm accordingly. This advancement makes it easier to implement effective vector control even with standard motors. Additionally, new technologies like torque vector control, adaptive control, and digital AVR techniques help improve low-speed performance and reduce speed deviations.
Overall, vector control has evolved significantly, providing precise and efficient control for AC motors across a wide range of applications.