Comparison of AC-Superconducting Multiphase Symmetric-Winding Topologies for Wind Power Generators With PM Rotors

Abstract

In this paper, an AC superconducting multi-phase symmetric-winding machine is designed for a wind power generator to improve its performance and reduce losses, where four handpicked topological designs were explored and compared. In particular, it is found that using high-phase order of unique phasors further improves the performance. The iron losses are reduced, and the rippling behavior is lowered due to the smoother airgap magnetic flux density. Furthermore, a higher least-common-multiple (LCM) is achieved due to a better slot-pole combination for fractional-slot concentrated windings without having space sub-harmonics. Nonetheless, it is shown that creating a smooth airgap magnetic flux density does not improve the AC hysteretic superconducting losses; thus, further research is needed using additional approaches. Moreover, it is found that the Meisner effect is present in the machine and is inversely proportional to the AC hysteretic superconducting losses. Finally, the work shows that a 13-phase AC-superconducting machine can achieve a theoretical limit approaching 101.70 Nm/kg for the torque-to-weight ratio, outperforming classic winding layouts.

Perspectives on Electric Machines with Cryogenic Cooling

“…The efficiency remains constant even at low loads, which is particularly important for ship propulsion, as ships employ around 30% of the maximum power at cruise speed. Additionally, the use of superconductors provides the potential to reduce the weight and volume of the motor, which can have a significant impact on the overall weight and size of the propulsion system; • Wind turbines: Superconducting generators could increase the power output of wind turbines [8], especially offshore ones, by reducing the size and weight of the generator and increasing the efficiency [9]. In the year 2019, by the EU H2020 EcoSwing project [9], the world's first rotor for a 3.6 MW wind generator was successfully tested.…”

“…Superconducting synchronous machines (SCSMs): These are synchronous machines that use superconducting windings in their rotor or stator. They can be used as generators [8] or motors [17], and provide high power density, high efficiency, and high power factor. Studies have shown that SCSMs can achieve efficiency levels of 99% at full load [7], compared to conventional motors that typically operate at around 94-96% efficiency;…”