Superconducting AC Homopolar Machines for High-Speed Applications

Kalsi, S.S.; Hamilton, Kent; Buckley, R. G.; Badcock, Rodney A.

doi:10.3390/en12010086

Cited by 34 publications

(26 citation statements)

References 17 publications

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“…Four different material law models have been systematically compared in [44], including (7) and (10). It is concluded that when at a low transport current (below 0.4 Ic0), the magnetization losses obtained by (7) and (10) are almost the same. In fact, (7) is in essence a simplified version of (10) with specific parameters.…”

Section: Magneto-angular Anisotropymentioning

confidence: 99%

Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines

Zhang

Mueller

2021

Supercond. Sci. Technol.

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Superconducting electric propulsion systems, characterized by high power densities and efficiencies, provide a possibility to zero carbon emission for future aviation. Stacks of high temperature superconductor (HTS) coated conductors (CCs) have become an alternative for high field magnets applied to superconducting machines, given their excellent field trapping ability and thermal stability. High-frequency ripple fields always exist in high-speed electric machines. Most research work regarding HTS trapped field stacks (TFSs) was focused on their magnetization methods and amplitude of trapped flux density; however, their performance in the high-frequency environment remains unclear. Despite several numerical models established for flat HTS TFSs, a comprehensive analysis of curved ones is still lacking, which possess geometrical applicability for cylindrical rotating shafts. Aimed at exploring the electromagnetic properties of curved HTS TFSs applied to high-speed rotating machines, a 3D numerical model considering both the multilayer structure and the Jc(B) dependence of HTS CCs has been built. Current and magnetic flux density distributions, as well as loss properties of a curved HTS TFS have been studied in detail, under perpendicular and cross fields with varying frequencies ranging from 50 Hz to 20 kHz. Results have shown that, the widely adopted 2D-axisymmetric models are inapplicable to study the electromagnetic distributions of TFSs because of the emergence of the electromagnetic crisscross defined in this paper. High-frequency ripple fields can drive induced current towards the periphery of the HTS TFS due to the skin effect, leading to a fast rise of AC loss and even an irreversible demagnetization of the stack. This paper has qualified and quantified the highfrequency electromagnetic hehaviours of curved HTS TFSs, providing a useful reference for their loss controlling and anti-demagnetization design in high-speed propulsion machines.

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Section: Magneto-angular Anisotropymentioning

confidence: 99%

Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines

Zhang

Mueller

2021

Supercond. Sci. Technol.

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“…The output power of an electrical machine is proportional to both rotational frequency and rotor excitation field [1]. The friction and heat generated by conventional bearings limit the design speed of any electrical machine.…”

Section: Introductionmentioning

confidence: 99%

Design, Build, and Evaluation of an AC Loss Measurement Rig for High-Speed Superconducting Bearings

et al. 2022

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Friction and heat generated in conventional bearings impose a limit on maximum design speed in electrical machines. Superconducting bearings offer the potential for low loss, simplified, and passively stable bearings that can overcome the speed limit and operate at high loads. Although such bearings are contactless and seem to be loss free, AC loss mainly caused by magnetic field inhomogeneity gradually slows down the rotating body. This loss, whose mechanism has not been fully explored, is measured through spin-down tests where the rotational speed of the spinning rotor is measured as a function of time. However, there are some challenges in performing a reliable spin-down test. In this paper, we discuss these challenges as well as the engineering of an experimental test rig that enables us to spin-up, release, and recapture the levitated permanent magnet. We also discuss the specifications of the driving mechanism including the self-aligning coupling, which accommodates permanent magnets of different sizes. Initial test results at 6600 rpm are discussed and further technical improvements to the test rig suggested. This rig will be used as a key tool to explore the AC loss mechanism and inform the design of bearings for high-speed superconducting machines.

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“…Synchronous homopolar machines have been known for a long time and are used in various equipment such as generators in aircrafts and trains [12], welding inverters [13], and flywheel energy storage systems [14]. Moreover, in [4,5,11,15,16], SHMs were presented as traction motors.…”

Section: Introductionmentioning

confidence: 99%

Design Optimization of a Traction Synchronous Homopolar Motor

et al. 2021

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Synchronous homopolar motors (SHMs) have been attracting the attention of researchers for many decades. They are used in a variety of equipment such as aircraft and train generators, welding inverters, and as traction motors. Various mathematical models of SHMs have been proposed to deal with their complicated magnetic circuit. However, mathematical techniques for optimizing SHMs have not yet been proposed. This paper discusses various aspects of the optimal design of traction SHMs, applying the one-criterion unconstrained Nelder–Mead method. The considered motor is intended for use in a mining dump truck with a carrying capacity of 90 tons. The objective function for the SHM optimization was designed to reduce/improve the following main characteristics: total motor power loss, maximum winding current, and torque ripple. One of the difficulties in optimizing SHMs is the three-dimensional structure of their magnetic core, which usually requires the use of a three-dimensional finite element model. However, in this study, an original two-dimensional finite element model of a SHM was used; it allowed the drastic reduction in the computational burden, enabling objective optimization. As a result of optimization, the total losses in the motor decreased by up to 1.16 times and the torque ripple decreased by up to 1.34 times; the maximum armature winding current in the motor mode decreased by 8%.

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Superconducting AC Homopolar Machines for High-Speed Applications

Cited by 34 publications

References 17 publications

Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines

Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines

Design, Build, and Evaluation of an AC Loss Measurement Rig for High-Speed Superconducting Bearings

Design Optimization of a Traction Synchronous Homopolar Motor

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