7.4 Indirect Rotor Field Oriented Control of Five-Phase Induction Motor
Field oriented control refers to the control technique in which an induction machine emulates as a DC machine. The torque and flux producing currents are decoupled and controlled independently, giving rise to fast dynamics of machine. This control technique is also called vector control, since the stator current space vector is controlled in this method. The detail description of field orientation and the vector control principle is discussed in Chapter 4. The purpose here is to distinguish between the control of a three-phase and a five-phase machine. Essentially, only two current components are required to produce torque in an induction machine, regardless of the phase number. In general, the d-axis current control of the flux in the machine is maintained constant for speed control in the base speed region and is reduced in appropriate proportion in the field weakening region (speed above the nominal or rated value). The q-axis current component controls the torque in the machine, since the d-axis current is kept constant (see equation (7.17)).
Since only two current components are needed for vector control, its principle remains the same for a multi-phase (more than three) machine as that of a three-phase machine. The only difference lies in the transformation of the current from two (α-β) to three (ia, ib, ic) in the case of a three-phase machine and two (α-β) to five (ia, ib, ic, id, ie) in a five-phase ...
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