Analysis of rotor shell losses in a magnetically levitated homopolar hollow-shaft permanent magnet synchronous motor (original) (raw)
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Magnetically Levitated Homopolar Hollow-Shaft Motor
IEEE/ASME Transactions on Mechatronics, 2000
This paper describes a novel and compact topology for contactless levitation and rotation of a wide annular rotor through the walls of a sealed process chamber. In the proposed setup, a homopolar magnetic bearing biased by permanent magnets is combined with a high-pole-number segment motor. The paper discusses the functional principle of the motor, and gives design and optimization guidelines for the bearing and the drive unit, respectively. An experimental system is presented along with a set of measurement results verifying the theoretical considerations.
Scaling of Magnetically Levitated Homopolar Hollow-Shaft Machines
2013
In this paper, we analyze scaling issues that arise when the size of a magnetically levitated hollow-shaft machine is varied, but the output power is kept constant. Reducing the size by a factor of two leads to a required increase in speed by a factor of about three. Because the losses of previously used topologies did not scale well we suggest and analyze a different topology: the combined homopolar magnetic bearing (CHB). The proposed design methodology has been experimentally verified in a prototype product.
The rotor eddy current losses of a high-speed permanent magnet synchronous motor reduce the efficiency of the motor and increase the temperature rise of the rotor. In severe cases, the permanent magnet of the rotor can be demagnetized, affecting the safe operation of the motor. In this paper, an analytical model of rotor eddy current losses calculation based on Maxwell equations is introduced. The eddy current losses of rotor structures, e.g., protection sleeve, shield layer and permanent magnets, are analyzed. The calculation results of rotor eddy current losses are compared with two-dimensional (2D) finite element analysis. The comparison verifies the accuracy and versatility of analytical calculation. Finally, the influences of the variables on eddy current losses in the derived model are analyzed. Based on the principle of minimizing eddy current losses, an optimized structure with copper layers covering both inner and outer surfaces of the protective sleeve is proposed. Furthermore, the optimized distribution parameter of copper film thickness is obtained.
ICEMS'2001. Proceedings of the Fifth International Conference on Electrical Machines and Systems (IEEE Cat. No.01EX501)
Certain types of PM electric machines are particularly susceptible to the proliferation of eddy currents flowing within the solid conducting regions in the rotor. These eddy currents can be induced by current winding harmonics, but also by the interaction of the static rotor magnetic field with the permeance variation of the slotted stator known as 'slotting'. This work focuses on the analytical calculation of eddy current loss that occurs in the conducting regions within a rotor under no-load conditions. The results are compared with finite element analysis and measured results from a machine test. Good agreement is achieved between the three methods of comparison. Index Terms-permanent magnet, eddy current, losses, slotting, rotor yoke, analytical, finite element. LIST OF SYMBOLS Symbol Quantity Unit A Magnetic vector potential V.s.m-1 B Flux density T H Magnetic field strength A.m-1 ωs Stator Synchronous Frequency radians t Time s µ Harmonic number Ns Number of Slots lm Machine length metres dsi Stator inner diameter metres ns Rotor speed rad.s-1 Np Number of poles ĸ Conductivity S.m-1 Rs Stator radius adjacent to airgap metres g' Effective airgap metres hy Yoke height metres µr Relative permeability J Current density A.m-2 Τs Segment width radians Ps Magnet segmentation penetration % Py Yoke Segmentation penetration % bsl Slot width radians τp Pole Pitch radians rmc Magnet centre radius metres hm Magnet height metres ls Segment length metres Nss Number of Segments Nrs Relative Degree of Segmentation µ0 Permeability of free space H.m-1 b0 Stator slot opening width radians Kw Winding factor Kc Carter Factor
Impact of the Rotor Yoke Geometry on Rotor Losses in Permanent-Magnet Machines
IEEE Transactions on Industry Applications, 2000
This paper presents a study on the rotor losses of surface-mounted permanent-magnet (PM) machine with fractionalslot windings. Two rotor losses sources are considered: the losses due to the slot opening (without currents in the stator) and due to the magneto motive force harmonics (mounting a rotor with demagnetized PMs). The rotor losses are measured at no load and under load. It is shown that the rotor losses under load are lower than considering the sum of the two contributions. This phenomenon is investigated using both analytical models and finite-element-based simulations. Then, the impact of the rotor geometry on the rotor losses is considered, and some design advices are reported.
2012 XXth International Conference on Electrical Machines, 2012
Φ Abstract --This paper describes a precise 2-dimensional analytical method for calculation of induced eddy current losses inside the rotor of high speed permanent magnet machines. Unlike Previous methods, the method introduced in this paper is flexible and can be used for any surface mounted permanent magnet machine with different rotor layers materials and dimensions. The method is primarily introduced by calculating the field of armature current for both space and time harmonics in the permanent magnet machine that is rotating at 130 Krpm with 30 KW of air gap power. Using the Poynting vector theorem, the induced eddy current loss is calculated in each layer of the rotor. Based on this method, the optimizations are performed on the rotor losses with respect to different rotor layers materials and dimensions and optimum rotor layers combinations and dimensions are achieved.
IEEE Access, 2020
In high speed permanent magnet (HSPM) machines, the computation of magnet eddy current loss is essential as these losses significantly affect the temperature of the permanent magnet (PM) and electromagnetic performance and can result in irreversible demagnetization of the PM. Several techniques have been adopted to minimize the eddy current loss of the PM; however, superior performance has not been achieved yet. In this paper, the design characteristics of the HSPM machine are analyzed. The PM is covered by a titanium sleeve to retain the PM on the rotor and to further reduce the eddy current loss of the magnet. The undesirable harmonics of the airgap flux density are minimized, which reduces the eddy current loss in the solid PM and rotor. Two existing models, with and without auxiliary slots, are examined and compared with the proposed design having a titanium-based retaining sleeve. The analysis reveals that the eddy-current loss, cogging torque, and iron losses of the PM are reduced by 82%, 73%, and 44.7%, respectively, in the proposed model; however, a marginal increase is observed in the average rated torque profile and open circuit flux linkage. INDEX TERMS Auxiliary slot, eddy current losses, finite element analysis, high speed machine, iron loss, permanent magnet, sleeve, spatial harmonics.
2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019
This paper deals with the electro-mechanical design of a high-speed-high-power (HSHP) electric motor. The focus is twofold: both mechanical and electromagnetic aspects are of interest. The former regards holding forces in order to sustain the retaining sleeve, components stresses, and rotordynamic behaviour of the rotor assembly. The latter addresses eddy current losses arising in different rotor parts. Usually different physics involving rotor losses, mechanical and thermal stresses are treated separately or superficially analysed with rules of thumbs approaches.This work addresses the lack of a comprehensive more detailed design treating mechanics and electromagnetic challenges together. The rotor under study is for an aerospace propulsion application known as Boundary-Layer-Ingestion (BLI).
Rotor Eddy-Current Loss in Permanent Magnet Brushless Machines
IEEE Transactions on Magnetics, 2004
This paper presents an analysis of the rotor eddycurrent loss in modular and conventional topologies of permanent magnet brushless machine. The loss is evaluated both analytically and by time-stepped finite-element analysis, and it is shown that it can be significant in both machine topologies. It is also shown that the loss can be reduced significantly by segmenting the magnets.
Energies
Eddy current losses in magnets are a major consideration in the rotor design of permanent magnet synchronous motors (PMSMs). Stator design choices and the use of modern inverters with high switching frequency introduce harmonics that can contribute to significant losses in the magnets, causing the rotor to heat up. In typical PMSMs, the lack of rotor cooling can cause the magnet’s performance to degrade at high temperatures and eventually demagnetize. This review examines a large number of studies analyzing magnet eddy current losses using analytical methods and finite-element analysis. In some of these studies, magnet segmentation is carried out to reduce the losses; however, their loss-reduction effects depend highly on the type of PMSM and the mix of stator harmonics. Magnet segmentation without considering these effects can, in fact, increase the magnet losses, in addition to the extra manufacturing efforts. Multiple design analysis show the influence of rotor–stator geometric f...