76 Frequency Converters 2.8.2 Danfoss Flux Vector Control Principle The principle of fl ux vector control assumes that a complete equivalent circuit diagram data is available. With this approach, all the relevant motor parameters are taken into account by the control algorithms. Considerably more motor data needs to be specifi ed than is the case with the basic VVCplus control. Changing a single parameter during commissioning switches the control algorithm from VVCplus control to fl ux vector control. Here more information needs to be fed in to the drive for smooth control of the motor. All parameters will not be explained here as they are fully explained in the operation manuals.
A brief description of the control strategy is shown in Fig. 2.27 Basic principles of Danfoss Flux Vector control. A fl ux database is stored in the frequency converter. The currents measured in all 3 phases are transformed in to polar coordinates (xy). Flux set point ψ n set control Speed n est Speed estimation Fig. 2.27 Basic principles of Danfoss Flux Vector control control USY Torque control Flux model