Mkhululi Mabhula

The revival of the old synchronous condenser (SC) technology is presently occurring. Hence, this study is proposed on the electromagnetic design and evaluation of turbo wound-field flux switching machines (WF-FSMs) for SC operation, for the first time. Unlike classical wound-field rotating machines, WF-FSMs do not need brushless exciters while possessing a robust topology. A design process based on the frozen permeability technique in static 2-D finite element analysis script-based package, which enhances both iterative and analytic adjudications, is proposed to accurately predict the SC operation. To attain the specific design requirements (~300 MVAR, 16 kV), a global-optimized model (GOM) of the SC machine is obtained through a stochastic optimization process involving multiple objectives. Based on the GOM, simple torque ripple minimization techniques are implemented, from which a final benchmark design is selected. The proposed SC analytical design procedure is then tested and the expected V-curves clearly obtained. The whole design approach is further verified by experimenting on a small-scale prototype, which when synchronized to the grid, confirms the novelty and feasibility of the proposed SC design and operation.

In this paper, a proposed numerical frozen permeability modeling procedure is fully derived to accurately estimate the parameters of two variants of wound-field flux modulation machines (WF-FMMs) namely: wound-field flux switching machine (WF-FSM) and DC-excited vernier reluctance machine (DC-VRM). During the procedure, the contribution of saturation to the variation of the machine parameters is investigated. The parameter variation effects on the machine performance is also investigated. It is shown that analysis of WF-FMMs is better understood by using the proposed procedure which computes accurately the machine parameters.

The study begins with a proposal to design a small-scale DC Vernier reluctance machine (DC-VRM) for direct-drive wind generator drives. The motivation centres on the increasing need for renewable energy technologies, as well as the quest for non-PM and gearless wind generator drives upon which the DC-VRM is uniquely compatible. A global optimisation is first undertaken based on solutions from 2D finite element modelling (FEM) to produce optimal benchmark designs (OBDs). The OBDs are further evaluated for independent performance improvement of the torque ripple using the simple rotor tooth-pairing technique. The findings show that the torque ripple can be drastically reduced when absolved from the integrated optimisation process. On the average, at 0.8 tooth-paring ratio, the torque ripple reduces by at least by 50 %, with observation of special quid pro quo effects in torque ripple and average torque generation of this machine. Already, 3D FEM simulations have been issued to draw out the end-effect discrepancies, while laboratory validation is still pending.

The paper details modern saturation modeling and performance calculation to the analysis of grid-connected cylindrical wound-rotor synchronous motors. The developed models give reliable results with limited computation effort. The finite element based method uses iterative procedures to calculate the motor performance during which the motor parameters are evaluated in detail. Experimental results prove that the method has a high degree of accuracy and is computationally efficient.

A basic, fast, and accurate steady-state finite-element analysis (FEA) based parameter and performance calculation method for the wound-rotor induction motor is presented. The method couples the circuit equations with field equations using the principle of frozen permeabilities to present the voltage-fed induction motor. The effects of saturation saliency and cross-magnetization are accurately taken into account. The method is verified by direct comparison with the current- and torque-slip frequency curves obtained from a commercial FEA package.