Vector Control: A Modern Method of Motor Management
Vector control is a relatively new but rapidly developing method of controlling the operation of synchronous and asynchronous electric motors. Compared to other methods, it has several advantages, although it requires additional hardware and software improvements. The mathematical foundation of this method was developed a long time ago, but the practical emergence of available structural components and systems based on them has only occurred in recent years.
Theoretical Basis and Distribution of Vector Control
The main theoretical foundation of the vector control algorithm was created by engineers from West Germany, who also developed many successful design solutions. In translated literature, the term "vector regulation" is often used, which is a calque from the German "Vektorregelung." However, in most cases, it is more accurate to use the term "vector control."
Principle of Operation of Vector Control
The vector control method allows for controlling not only the amplitude, frequency, and phase of the alternating voltage on the motor windings but also the magnetic flux in the rotor, which influences the torque at the motor shaft. This is particularly useful when the load on the shaft frequently changes within wide limits. Examples of such situations can include drives for pumps, concrete mixers, elevators, and belt conveyors. Vector control provides increased regulation accuracy, speed of response to load changes, and smooth operation of the system.
Equipment and System Requirements
To implement vector control, sensors need to be installed within the motor, and the information from these sensors is transmitted to the power device. The most common systems are those where the power supply voltage is provided by a frequency converter. This device generates voltage of a certain frequency and amplitude, which determines the operating mode of the asynchronous motor.
However, a sensorless vector control scheme is also possible.
Advantages of Vector Control
The main advantages of the vector control method for motors include:
- High precision in controlling the angular speed of the motor shaft;
- Smooth start-up, stop, and speed change;
- Quick response to load changes;
- Expanded regulation range;
- Reduction in the spikes of starting currents;
- Reduction of losses due to magnetization and heating, leading to increased efficiency of the motor and the system as a whole.
Impact on Industry
In most industrially developed countries, new asynchronous electric motors for power drives are practically no longer produced without a built-in frequency converter or a soft start device. Most of these devices are capable of implementing the vector control algorithm for the motor as one of the operating modes.