Outer-rotor ac homopolar motors for flywheel energy storage

Severson, Eric L.; Nilssen, Robert; Undeland, Tore; Mohan, Ned

doi:10.1049/cp.2014.0345

Cited by 22 publications

(20 citation statements)

References 16 publications

(27 reference statements)

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“…A prototype has been demonstrated to offer an efficiency of 83% at 9.4 kW over 30,000-60,000 rpm. Recently, the homopolar machine has been further extended to adopt the outer-rotor topology, hence improving the energy density for the FESS [53].…”

Section: On-board Energy Storagementioning

confidence: 99%

State-of-the-Art Electromagnetics Research in Electric and Hybrid Vehicles (Invited Paper)

Chau¹,

Jiang²,

Han³

et al. 2017

PIER

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Abstract-There is no doubt that electrified vehicles are superseding internal combustion engine vehicles for road transportation. Among them, electric vehicles (EVs) have been identified as the greenest road transportation while hybrid EVs have been tagged as the super ultra-low emission vehicles. In this paper, the definition, classification, merits and demerits of electric and hybrid vehicles are first introduced. Then, after revealing their multidisciplinary technologies and development trends, the state-of-the-art electromagnetics research in electric and hybrid vehicles are discussed, with emphasis on electric motors for electric propulsion, electric machine systems for hybrid propulsion, wireless power transfer technologies for park-and-charge a well as move-and-charge, electromagnetic interference and compatibility issues in EVs, electromechanical flywheels for energy storage and magnetic sensors for EV operation. Meanwhile, the development trend of these research areas is revealed.

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Section: On-board Energy Storagementioning

confidence: 99%

State-of-the-Art Electromagnetics Research in Electric and Hybrid Vehicles (Invited Paper)

Chau¹,

Jiang²,

Han³

et al. 2017

PIER

View full text Add to dashboard Cite

show abstract

“…These features must be weighed against the motor's low torque density, which arises from the fact that it only utilizes onehalf of the iron's magnetic circuit at any location. It has been shown in [19] that for designs where minimum loss is a key objective, the ac homopolar motor can achieve nearly the same torque density as conventional synchronous motors. There has been recent interest in implementing the ac homopolar motor as a high-speed machine, a super-conducting machine, and a high-frequency generator [19]- [22].…”

Section: Bearingless Ac Homopolar Motormentioning

confidence: 99%

“…It has been shown in [19] that for designs where minimum loss is a key objective, the ac homopolar motor can achieve nearly the same torque density as conventional synchronous motors. There has been recent interest in implementing the ac homopolar motor as a high-speed machine, a super-conducting machine, and a high-frequency generator [19]- [22]. As a bearingless machine, work has focused on considering this machine in applications where magnetic bearings are typically required [7], [23]- [26].…”

Section: Bearingless Ac Homopolar Motormentioning

confidence: 99%

“…As a bearingless machine, work has focused on considering this machine in applications where magnetic bearings are typically required [7], [23]- [26]. The authors of this work are interested in using the machine in a flywheel energy storage system, where concerns regarding magnetic losses alleviate the torque density trade-off [19]. Furthermore, unlike the conventionally-used PM motor, the ac homopolar motor's current-based excitation can be reduced during times of idling to nearly eliminate self-discharge.…”

Section: Bearingless Ac Homopolar Motormentioning

confidence: 99%

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Dual-Purpose No-Voltage Winding Design for the Bearingless AC Homopolar and Consequent Pole Motors

Severson

Nilssen

Undeland

et al. 2015

IEEE Trans. on Ind. Applicat.

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A winding design approach is proposed for the bearingless ac homopolar and consequent pole motors that utilizes the same coils for both suspension force and torque production. This enables a "pure" bearingless motor design, where the same iron and copper are used for both magnetic bearing operation and torque production, and can result in more optimal machine performance. Separate terminal connections are provided for suspension and torque operation; the suspension terminals experience no motional-emf when the rotor is centered, thereby reducing the required voltage rating of the bearingless drive compared to other "dual purpose" winding designs. It is shown that only certain combinations of stator slots, phases, and poles yield suitable winding designs; most notably, the number of motor pole-pairs must be co-prime with the number of phases. A design procedure is proposed which allows the designer to simply modify end-connections of many conventional armature windings, including both integral-and fractional-slot windings; an example winding design is presented and analyzed using 3D finite element analysis (FEA); and a hardware prototype has been constructed with experimental results included to validate the proposed design approach.

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“…Furthermore, the ac homopolar machine has a simple and robust rotor structure, making it conducive to high-speed operation and, thereby, enabling flywheel designs with high energy density. While it is well known that the ac homopolar machine suffers from a low-torque density compared to PM machines, it has been shown in [13] that when the machine design is optimized for low magnetic losses (which is the case for flywheel systems), a design based around the ac homopolar machine will achieve similar torque densities to those based around PM machines.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Equivalent Circuit Modeling of the AC Homopolar Machine for Flywheel Energy Storage

Severson

Nilssen

Undeland

et al. 2015

IEEE Trans. Energy Convers.

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This paper develops a magnetic equivalent circuit model suitable to the design and optimization of the synchronous ac homopolar machine. The ac homopolar machine is of particular interest in the application of grid-based flywheel energy storage, where it has the potential to significantly reduce self-discharge associated with magnetic losses. The ac homopolar machine features both axial and radial magnetizing flux paths, which requires finite element analysis to be conducted in 3-D. The computation time associated with 3-D finite element modeling is highly prohibitive in the design process. The magnetic equivalent circuit model developed in this paper is shown to be a viable alternative for calculating several design performance parameters and has a computation time which is orders of magnitude less than that of 3-D finite element analysis. Results obtained from the developed model are shown to be in good agreement with finite element and experimental results for varying levels of saturation.Index Terms-Energy storage, finite element analysis, flywheels, magnetic equivalent circuit (MEC), renewable generation. ;).R. Nilssen and T. Undeland are with the Department of Electric Power Engineering,

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Outer-rotor ac homopolar motors for flywheel energy storage

Cited by 22 publications

References 16 publications

State-of-the-Art Electromagnetics Research in Electric and Hybrid Vehicles (Invited Paper)

State-of-the-Art Electromagnetics Research in Electric and Hybrid Vehicles (Invited Paper)

Dual-Purpose No-Voltage Winding Design for the Bearingless AC Homopolar and Consequent Pole Motors

Magnetic Equivalent Circuit Modeling of the AC Homopolar Machine for Flywheel Energy Storage

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