Advanced Electrical Drives by Rik W. De Doncker & Duco W. J. Pulle & André Veltman

Author:Rik W. De Doncker & Duco W. J. Pulle & André Veltman
Language: eng
Format: epub
ISBN: 9783030489779
Publisher: Springer International Publishing

Current-Speed Diagram

An alternative approach to the use of the current locus diagram for representing the current locus is to consider the normalized direct and quadrature current components as function of the normalized (with respect to the base speed) shaft speed. The so-called current-speed diagram is given in Fig. 7.6. In this diagram, the green and red curves correspond to the maximum direct and quadrature axis currents at the given speed. They encompass the MTPA line (motoring only) up to the maximum torque point and then along the MA circle. The red dotted curve represents the base speed equation (7.13). The intersection of this line with the selected quadrature current value occurs at speed ωsA above which field weakening must be used. The green dashed curve represents the quadrature component of the MTPF line. The blue colored lines show the normalized direct current and the normalized quadrature current for currents that correspond to operation with half maximum torque. In the current locus diagram these lines correspond to the trajectory 0 →A →B and part of the trajectory B →C (C is reached when ω s →∞). Included in Fig. 7.6 is operating point E which identifies the speed from where operation along the MTPF trajectory is feasible. The diagram shows that the d-axis current is equal to the short circuit current for . It further shows that the quadrature current curve coincides with the q-component of the MTPF trajectory as defined in current locus diagram for .

Fig. 7.6Current-speed diagram: operational drive trajectory for non-salient synchronous drives with

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