Rajesh P. Deodhar

Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed.

A Novel Hybrid-Excited Switched-Flux Brushless AC Machine for EV/HEV Applications

A novel E-core hybrid-excited switched-flux permanent-magnet (SFPM) brushless machine is proposed based on an E-core SFPM machine, which has significantly less magnet and higher torque density than those of a conventional SFPM machine. The proposed machine has a simple structure. The main flux path of dc excitation does not affect the magnet excitation because it is not through magnets. The combination of stator and rotor pole numbers of the proposed machine is optimized, and the flux-enhancing and flux-weakening capabilities are investigated by 2-D finite-element analyses and experimentally validated.

Torque prediction using the flux-MMF diagram in AC, DC, and reluctance motors

This paper uses the flux-MMF diagram to compare and contrast the torque production mechanism in seven common types of electric motor. The flux-MMF diagram is a generalized version of the flux-linkage versus current (/spl psi/-i) diagram for switched-reluctance motors. It is illustrated for switched-reluctance, synchronous-reluctance, induction, brushless AC, brushless DC, interior PM and commutator motors. The calculated flux-MMF diagrams for motors with the same electromagnetic volume, airgap, slotfill, and total copper loss are shown and are used to compare the low-speed torque and torque ripple performance. The motor designs used were reasonably optimized using a combination of commercially available motor CAD packages and finite-element analysis.

Influence of PWM on the Proximity Loss in Permanent-Magnet Brushless AC Machines

A winding copper loss can be significantly increased due to skin and proximity eddy-current effects. The skin and proximity losses due to fundamental frequency current have been investigated in literature, but the influence of pulsewidth modulation (PWM) on the skin and proximity losses has not been reported. In this paper, a 2-D finite element method is employed to analyze the skin and proximity losses in a permanent magnet brushless ac machine, in which significant proximity loss exists due to high frequency current ripples induced by the PWM, as confirmed by both theoretical calculation and experiment. The analyses should be generally applicable to other machines.

A Novel E-Core Switched-Flux PM Brushless AC Machine

A novel E-core switched-flux permanent-magnet (SFPM) brushless machine is proposed, and its electromagnetic performance is compared with that of the conventional SFPM brushless machine. The operation principle of the E-core SFPM machine will be first described, and the influence of stator and rotor pole number combinations is investigated, while the electromagnetic performance of the optimized E-core SFPM machine is predicted by finite-element analyses and validated by experiment. It is shown that the number and volume of magnets in the E-core SFPM machine is significantly reduced, only half of that in the conventional machine, while the phase back electromotive force and torque of the E-core machine are ~15% larger than those of the conventional machine.

Influence of Slot Opening on Optimal Stator and Rotor Pole Combination and Electromagnetic Performance of Switched-Flux PM Brushless AC Machines

The significant influence of slot opening on the optimal stator and rotor pole combination and on the electromagnetic performance of the switched-flux permanent magnet (SFPM) machine is observed and investigated in this paper. A new SFPM brushless machine with remarkable slot opening relative to the magnet thickness is developed to reduce the magnet usage and to increase the slot area. Its stator slot opening is almost several times of that in the conventional SFPM machine, but its magnet usage is only half. However, the new machine exhibits ~ 40% larger back EMF and electromagnetic torque than those of the conventional machine, while its cogging torque and torque ripple are significantly lower.

Low cost flux-switching brushless AC machines

A low cost 3-phase DC winding excited flux-switching (FS) brushless AC machine is developed from the FS permanent magnet (FSPM) machine. The influence of stator and rotor pole number combination on its electromagnetic performance, including flux-linkage and back-emf waveforms, electromagnetic static torque, and torque-current density characteristics, are predicted by 2-D finite element analyses and validated by experiment. In addition, the torque capability of the FS machine and FSPM machines with rare earth and ferrite magnets, respectively, are compared by the finite element analyses. It is found that whilst it is low cost, the torque capability in the FS machine may be limited by the significant magnetic saturation in the stator teeth.

Comparison of losses and efficiency in alternate flux-switching permanent magnet machines

The performance of the optimized conventional, novel E- and C-core flux-switching permanent magnet (FSPM) machines having different combination of stator and rotor pole numbers is compared by finite element analyses, with particular reference to the conductor and magnet eddy current loss and iron loss. Both iron loss and conductor eddy current loss increase with the rotor pole number, while the 11- and 13-rotor pole machine always exhibit lower magnet eddy current loss than those of the 10- and 14-rotor pole machine, respectively. The E- and C-core machines use half number and volume of magnets but exhibit higher efficiency than those of the conventional FSPM machine.

A novel E-core flux-switching PM brushless AC machine

A novel E-core flux-switching PM (FSPM) brushless machine is proposed, and its electromagnetic performance is compared with that of the conventional FSPM brushless machine. The operation principle of the E-core FSPM machine will be firstly described and the influence of stator and rotor pole number combinations is investigated, while the electromagnetic performance of the optimized E-core FSPM machine is predicted by finite element analyses and validated by experiment. It is shown that the number and volume of magnets in the E-core FSPM machine is significantly reduced - only half of that in the conventional machine, while the phase back-emf and torque of the E-core machine are ∼15% larger than those of the conventional machine.

Eddy Current Loss in the Frame of a Flux-Switching Permanent Magnet Machine

In flux-switching permanent magnet machines, a significant leakage flux exists at the outer surface of the stator core. Since the leakage flux varies as the rotor rotates, a significant eddy current loss may be induced in the nonmagnetic frame. The leakage flux and the associated eddy current loss in a representative flux-switching machine are investigated by finite element analysis, on both open-circuit and at rated load, predicted results being validated experimentally. In addition, the effectiveness of introducing slots in the frame to reduce the eddy current loss is investigatedThe leakage flux and resultant eddy current loss in the frame of a flux-switching permanent magnet (FSPM) motor was investigated by 2D time-domain finite element analysis and validated experimentally. This paper presents predicted and measured results for eddy current loss in the frame during both low speed, constant torque operation and high speed, constant power (flux-weakening) operation.