Doubly-Salient Permanent Magnet Flux-Reversal-Free-Stator Switched Reluctance Machines

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Virginia Tech


A new hybrid machine having variable reluctance and permanent magnets (PMs) is presented. The machine makes use of the features of a PM machine and variable reluctance machine. The resulting machine is doubly salient and has a structure free of flux reversals. Unlike conventional doubly salient permanent magnet machines (DSPMs), the one proposed in this report is driven by unipolar currents and uses an asymmetric converter which is used to drive switched reluctance machines. The reason to have a new hybrid machine without the drawbacks of conventional flux-reversal-free-stator SRMs and conventional DSPMs is also described.

Conventional doubly salient permanent magnet machines which are driven by alternating currents, do not use reluctance torque and have flux reversals in the stator iron. Homopolar flux at the peak flux density lowers hysteresis and eddy-current loss, since the machine's core operates in only one magnetizing quadrant. Due to unbalanced forces in conventional stator-flux-reversal-free machines, their deployment in industrial and end-user applications has been hindered. The presented hybrid machine has balanced radial forces. Therefore, it maintains the advantages of conventional stator-flux-reversal-free machines while shedding its disadvantages. The proposed machine has significantly increased power density and is more electromechanically efficient than its predecessor. A experimental prototype motor has been designed and built. Its static torque characteristics correlated well with predicted data. Experimental operation of the drive under open loop speed control shows the efficiency to be 90.8% under non-ideal driving conditions. In the current energy conscious environment and market, this motor because of its high efficiency has a significant role in reducing the energy consumption in household, industrial and automotive applications requiring electric motors.



Doubly salient permanent magnet motor, Switched reluctance motor