Three-phase voltage source inverter
Field oriented control (FOC) technology is popular in the three-phase AC motor，which to achieve fast dynamic response. The technical solution imitate the work of DC motor, the working principle is based on the complete decoupling of two current components: squirrel-cage motor torque generated in the magnetic flux generating current component and the current component. This contains the required external components. Using Clarke and Park transformation can convert the three time-varying output current (ia, ib, ic) into 2 time-invariant values (Id, Iq). Thus, the final DC value will be controlled easily. The difference between the measured value of Current component and the expected value depends on the speed induction motor required.
Sensor less control technology of AC motor is still a subject of concern and a growing area of research. In the case of use of IM, sensor less control can be simplified, because the squirrel-cage motor location is not necessary for the motor work. If you need speed control, the rotor position can be calculated directly through the so-called back-EMF (BEMF).
