The scalar control method is based on varying two parameters simultaneously. This speed can be varied by increasing or decreasing the supply frequency, though this results in a change of impedances. This change of impedances then also increases or decreases the current. If the current is small, the motor torque decreases. If the frequency decreases or the voltage increases, the coils can be burned or saturation can occur in the iron of the coils. To avoid these problems, it is necessary to vary the frequency and the voltage at the same time.
Field-oriented vector control makes it possible to uncouple the field components into two independent, single-controlled currents instead: The flux-producing current and the torque producing current. With vector-based control, you can achieve tighter speed control, higher starting torque, and higher low-speed torque.
There are advantages and disadvantages to both methods. Scalar control is cheap and easy to implement, though it is not as sufficient in controlling drives with dynamic behavior. Overall, scalar is low-performance, but stable.
On the other hand, with field-oriented vector, you can control the currents independently, allowing it to operate with fast responses, making it much more appropriate for dynamic drives. In this case, vector is more costly and complex, but the higher-performing mode of the two.
At the end of the day, which control mode you should choose will depend on the specific requirements of your application.
For more information about using scalar or vector control, or to get assistance choosing a control method for your application, contact our experts today!