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Influence of curvature on air-gap magnetic field distribution and rotor losses in pm electric machines

Influence of curvature on air-gap magnetic field distribution and rotor losses in pm electric machines
Influence of curvature on air-gap magnetic field distribution and rotor losses in pm electric machines
Purpose – The purpose of this paper is to study the effect of curvature on the magnetic field distribution and no-load rotor eddy-current losses in electric machines, particularly in the case of high-speed permanent magnet machines.

Design/methodology/approach – The magnetic field distribution is obtained using conformal mapping and eddycurrent losses are obtained using a cylindrical multilayer model. The analytical results are validated using 2D FEA. The analytical method is based on a proportional-logarithmic conformal transformation that maps the cylindrical geometry of a rotating electric machine into a rectangular configuration without modifying the length scale. In addition, the appropriate transformation of permanent magnet (PM) cylindrical domains into the rectangular domain is deduced. Based on this conformal transformation a coefficient to quantify the effect of curvature is proposed.

Findings – Neglecting the effect of curvature can produce significant errors in the calculation of no-load rotor losses when the ratio between the air-gap length and the diameter of the rotor is large.

Originality/value – The appropriate transformation of permanent magnet (PM) cylindrical domains into the rectangular domain is deduced. The proportional-logarithmic transformation proposed provides an insight into the effect of curvature on the magnetic field distribution in the air-gap and no-load rotor losses. Furthermore, the proposed curvature coefficient gives a notion of the effect of curvature for any particular geometry without the necessity of any complicated calculation. The case study shows that neglecting the effect of curvature underestimates the rotor eddy current losses significantly in machines with large gap to rotor diameter ratios.
Conformal mapping, permanent magnet machines, rotor eddy-current power loss calculation
0332-1649
871-891
Anglada, J.R.
4ba2df6e-f91f-4ffc-8169-068852e59e90
Sharkh, S.M.
c8445516-dafe-41c2-b7e8-c21e295e56b9
Qazalbash, A.A.
c0f21e32-a599-4997-af6d-8775c0586557
Anglada, J.R.
4ba2df6e-f91f-4ffc-8169-068852e59e90
Sharkh, S.M.
c8445516-dafe-41c2-b7e8-c21e295e56b9
Qazalbash, A.A.
c0f21e32-a599-4997-af6d-8775c0586557

Anglada, J.R., Sharkh, S.M. and Qazalbash, A.A. (2017) Influence of curvature on air-gap magnetic field distribution and rotor losses in pm electric machines COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 36, (4), pp. 871-891. (doi:10.1108/COMPEL-05-2016-0200).

Record type: Article

Abstract

Purpose – The purpose of this paper is to study the effect of curvature on the magnetic field distribution and no-load rotor eddy-current losses in electric machines, particularly in the case of high-speed permanent magnet machines.

Design/methodology/approach – The magnetic field distribution is obtained using conformal mapping and eddycurrent losses are obtained using a cylindrical multilayer model. The analytical results are validated using 2D FEA. The analytical method is based on a proportional-logarithmic conformal transformation that maps the cylindrical geometry of a rotating electric machine into a rectangular configuration without modifying the length scale. In addition, the appropriate transformation of permanent magnet (PM) cylindrical domains into the rectangular domain is deduced. Based on this conformal transformation a coefficient to quantify the effect of curvature is proposed.

Findings – Neglecting the effect of curvature can produce significant errors in the calculation of no-load rotor losses when the ratio between the air-gap length and the diameter of the rotor is large.

Originality/value – The appropriate transformation of permanent magnet (PM) cylindrical domains into the rectangular domain is deduced. The proportional-logarithmic transformation proposed provides an insight into the effect of curvature on the magnetic field distribution in the air-gap and no-load rotor losses. Furthermore, the proposed curvature coefficient gives a notion of the effect of curvature for any particular geometry without the necessity of any complicated calculation. The case study shows that neglecting the effect of curvature underestimates the rotor eddy current losses significantly in machines with large gap to rotor diameter ratios.

Text __filestore.soton.ac.uk_users_fh1d15_mydesktop_paper_curvature.pdf - Accepted Manuscript
Restricted to Repository staff only until 12 March 2018.

More information

Accepted/In Press date: 21 November 2016
e-pub ahead of print date: 3 July 2017
Keywords: Conformal mapping, permanent magnet machines, rotor eddy-current power loss calculation
Organisations: Mechatronics

Identifiers

Local EPrints ID: 404898
URI: http://eprints.soton.ac.uk/id/eprint/404898
ISSN: 0332-1649
PURE UUID: 39ec9ebb-c26b-4afb-910a-09285854bc7e

Catalogue record

Date deposited: 24 Jan 2017 16:18
Last modified: 16 Nov 2017 17:32

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Contributors

Author: J.R. Anglada
Author: S.M. Sharkh
Author: A.A. Qazalbash

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