Application of Fractional-Slot Concentrated Windings to Synchronous Reluctance Motors

Abstract

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Synchronous reluctance motor technology: industrial opportunities, challenges and future direction

“…One stream of research in advancing synchronous reluctance motor technology is to migrate from distributed windings on the stator to a fractional slot-concentrated winding [27,28], which involves winding highly concentrated coils such as those found on the rotor of a salient pole alternator, but applied to the stator of the synchronous reluctance motor. Usually the choice for high torque, low speed modern permanent magnet motors [29,30], the fractional slot-concentrated winding utilises coils that span a single stator tooth.…”

“…This machine has been shown to exhibit high torque density and higher efficiency for the same 18 frame size compared to both the induction motor and the conventionally wound synchronous reluctance machine [26,27,28]. The main benefits of adopting this cSynRM topology of machine are as follows; At an initial glance, the topology appears to be very desirable, the short end winding due to their short span now contain less copper and do not overlap other phases, aiding electrical isolation and neat coils to be wound -effectively enabling higher slot fill factors, upwards 80% in some cases when compressed coils are utilized [31].…”

“…Through good electromagnetic design, the torque ripple can be reduced [32,38,42] and the power factor improved, though when using direct torque control such as with the ABB marketed SynRM [9], the torque ripple problem can be reduced but the power factor challenge remains. In summary, the main drawbacks of adopting the cSynRM topology are [27];…”

“…The topology has been shown to allow up to a +3% efficiency increase [26] for the same output than the conventional SynRM and up to 25% increase in torque density can be achieved with a 60% fill factor [27,28] without the requirement for permanent magnets. The cSynRM tackles some of the conventional SynRM's undesirable characteristics and is a promising prospect, however further development is required to bring this technology to market.…”

“…These are highly important works and should be considered in any serious study of this machine; Kostko [10] [27,28,32]. This list is by no means comprehensive, but serves as a useful bibliography as an extension to the introduction to the subject.…”