Search results

The purpose of this paper is to investigate winding topologies for flux-switching motors (FSMs) with various segment-tooth combinations and different excitation methods.

For the ac winding of FSM, two winding topologies, namely the concentrated winding and the distributed winding, are compared in terms of the winding factor and efficiency. For the field winding of dc-excited FSM (DCEFSM), another two winding topologies, namely the lap winding and the toroidal winding, are compared in terms of effective coil area, end-winding length, and thermal conditions. Analytical derivation is used for the general winding factor calculation. The calculation results are validated using finite element analysis.

Winding factors can be used as an indication of winding efficiency for FSMs in the same manner as done for synchronous motors. For FSMs with concentrated windings, the winding factor increases when the rotor tooth number approaches a multiple of the stator segment number. For FSMs with certain segment-tooth combinations, e.g. 6/8, the theoretical maximum winding factor can be achieved by implementing distributed windings. Furthermore, the toroidal winding can be an efficient winding topology for DCEFSMs with large stator diameter and small stack length.

This work can be continued with investigating the variation of reluctance torque with respect to different segment-tooth combinations of FSM.

This paper proposes a general method to calculate the winding factor of FSMs using only the phase number, the stator segment number, the rotor tooth number, and the skew angle. Using this method, a table of winding factors of FSMs with different segment-tooth combinations is provided. Principle of design of FSMs with high-winding factors are hence concluded. This paper also proposed the implementation of distributed windings for FSM with certain segment-tooth combinations, e.g. 6/8, by which means a theoretical maximum winding factor is achieved. In addition, different winding topologies for the field winding of DCEFSM are also investigated.

This paper aims to find the optimal winding topology for a 14‐pole permanent magnet synchronous motor (PMSM) to be used as an in‐wheel motor in automotive applications.

Comparison is first performed among lap windings with different combinations of slot numbers and pole numbers. A general method for calculating the winding factors using only these numbers is proposed, thus the preferable slot numbers resulting in relatively large winding factors for this 14‐pole PMSM are found. With these slot numbers, the Joule losses of armature windings are further investigated, where the impacts of different end‐winding lengths are considered. By this means, the optimal slot number that causes the least Joule loss is obtained. On the other hand, as a competitor to lap windings, toroidal windings are also discussed. The thermal performances of these two types of windings are compared by performing a finite element analysis (FEA) on their 2‐D thermal models.

For the 14‐pole in‐wheel PMSM discussed in this paper, the preferable slot numbers leading to relatively large winding factors are 12, 15 and 18. However, with the specified geometry constraints, the optimal choice of slot number is 15, which results in the least Joule loss and thus the highest efficiency. On the other hand, by implementing the toroidal winding topology, the armature windings of this machine can be effectively cooled and thus allow a larger electrical loading than the lap windings do.

This work can be continued with investigating the impacts of different combinations of slot number and pole number on harmonics and cogging torques.

This paper proposes a general method for calculating the winding factor of PMSMs using only the phase number, the slot number, and the pole number. With this method, the calculation procedure can be easily programmed and repeated.

The aim of this paper is to provide a simple yet accurate and efficient geometric method for thermal homogenization of impregnated and non-impregnated coil winding technologies based on the concept of thermal resistance.

For regular windings, the periodic microscopic cell in the winding space is identified. Also, for irregular windings, the average microscopic cell of the winding is determined. An approximation is used to calculate the thermal resistance of the winding cell. Based on this approximation, the winding insulation is considered as a circular ring around the wire. Mathematical equations are obtained to calculate the equivalent thermal resistance of the cell. The equivalent thermal conductivity of the winding is calculated using equivalent thermal resistance of the cell. Winding thermal homogenization is completed by determining the equivalent thermal properties of the cell.

The thermal pattern of different windings is simulated and compared with the results of different homogenization methods. The results show that the proposed method is applicable for a wide range of windings in terms of winding scheme, packing factor and winding insulation. Also, the results show that the proposed method is more accurate than other winding homogenization methods in calculating the equivalent thermal conductivity of the winding.

In this paper, the change of electrical resistance of the winding with temperature and thermal contact between the sub-components are ignored. Also, liquid insulators, such as oils, and rectangular wires were not investigated. Research in these topics is considered as future work.

Unlike other homogenization methods, the proposed method can be applied to non-impregnated and irregular windings. Also, compared to other homogenization methods, the proposed method has a simpler formulation that makes it easier to program and implement. All of these indicate the efficiency of the proposed method in the thermal analysis of the winding.

The purpose of this paper is to investigate advantages of multiphase permanent magnet synchronous motors (PMSM) with fractional slot concentrated windings (FSCW). The investigation is based on comparative analysis and assessment of FSCW PMSM wound as 3, 6, 9 and 12 phase machines suited for low speed applications.

The investigations are focussed on distortions of back electromotive (emf) and magnetomotive force (mmf) with the torque ripples and motors’ performance taken into account. The finite element models with the aid of customized computer code have been adopted for motor winding design and back emf, mmf and motor performance analyses.

The novel multiphase winding layouts were found to offer lower content of sub-harmonics in the mmf waveforms compared with the traditional three-phase machine designs. Moreover, the investigated multiphase machines exhibited higher average value of the electromagnetic torque, while the multiphase PMSM machines with FSCW were further characterized by significantly lower torque pulsations.

The analyses presented in this paper demonstrate that PMSM with FSCW are advantageous to their counterpart three-phase machines. Specifically, they offer higher performance and are more suitable to work with multiple drives supplying segmented winding system. This ability of using multi-drive supply for one motor offers flexibility and cost reduction while increasing fault tolerant power train system.

The purpose of this paper is to present a general review of design guidelines and analytical models for permanent‐magnet synchronous machines (PMSMs) with non‐overlapping concentrated windings, including the authors' own experience.

The design features specific to three‐phase PMSMs with non‐overlapping concentrated windings are presented following the proposed chronology for the different choices to be made by motor designers.

It is shown that the selections of the stator core manufacturing method, the number of winding layers, the combination of pole and slot numbers, and the geometry of the tooth tips are crucial during the design stage of the machine. Comprehensive lists of references introducing useful analytical models and prototypes presented in literature are provided.

By following the guidelines provided in the paper, motor designers are able to avoid the known drawbacks of PMSMs with non‐overlapping concentrated windings, and have a ready list of sources describing useful analytical models.

PMSMs with non‐overlapping concentrated windings have recently been widely investigated. This paper provides an overview of the main results, pinpointing the choices encountered by the motor designers.

An excessive increase in temperature will reduce the lifespan and even burn the coil. The variety of materials in the structure of the electromagnet along with its multi-layer winding creates a complex and heterogeneous thermal structure. There are very few researches that are completely focused on the thermal analysis of electromagnets. The purpose of this paper is to provide an accurate, yet fast and simple method for the thermal analysis of cylindrical electromagnets in both transient and steady-state modes. For this purpose, a thermal equivalent circuit (TEC) is presented based on the nodding approach.

The results of TEC analysis of cylindrical electromagnet, for two orthogonal and orthocyclic winding coil technologies, were compared with the results of the thermal simulation in COMSOL. The authors also built a laboratory model of the cylindrical electromagnet, similar to those analyzed and simulated, and measured the temperature in different parts of it.

The comparison of the results obtained from different methods for the thermal analysis of the cylindrical electromagnet indicates that the proposed TEC has an error of less than 2%. The simplicity and high accuracy of the results are the most important advantages of the proposed TEC.

Comparing the information and results related to winding schemes, indicates that the orthogonal winding has less cost and weight due to the shorter length of the wire used. On the other hand, orthocyclic winding generates lower temperature and has more lifting force, and is simpler to implement. Therefore, in practice, orthocyclic winding technology is usually used.

This paper aims to propose an analytical model for the harmonic content no-load magnetic fields and Back electric motive force (EMF) in double-sided TORUS-type non-slotted axial flux permanent magnet (TORUS-NS AFPM) machines with surface-mounted magnets considering the winding distribution and iron saturation effects.

First, a procedure to calculate the winding distribution with a rectangular cross-section is proposed. The magnetic field distribution and magnetic motive force (MMF) drop due to saturation in iron cores are then exactly extracted in a 2-D analytical model. The consequent influence on air-gap magnetic field and Back EMF are also calculated using a new iterative algorithm. The results are compared with those of the conventional analytical model without saturation, 2-D finite element analysis (FEA) and an experiment on a fabricated prototype machine.

Unlike the conventional method, the new method yields the no-load magnetic field distributions in air-gap and iron cores and Back EMF very exactly such that the results well match to those of the FEA and experiment.

Unlike the conventional winding factor, the winding distribution is considered here along the both axial and circumferential directions, which improves the accuracy level of results for non-slotted structures with relatively large air-gaps. The magnetic field distribution and MMF drop-in iron parts are also calculated as the basis for exact recalculation of air-gap magnetic field and Back EMF. Because of small computational burden beside superior accuracy, the proposed model can be treated as an accurate and fast substitute for FEA to be used during the design procedure or for predicting the other performance characteristics of TORUS-NS AFPM machines.

The purpose of this paper is to discuss the performance of a proposed machine design for an in‐wheel motor with the required torque‐speed characteristic.

Calculation of the winding factor of the machine with the star of slots theory is performed first. The field weakening capability of the machine is investigated and the operating speed range is determined. The tooth contour modeling method for calculating the performance of the machine with a limited number of elements is introduced. The method is used to construct two models of different complexity and the results obtained with the models are compared with the results obtained by finite element models.

The 14 pole 12 slot in‐wheel PMSM discussed in this paper is able to meet the stringent performance requirements. The results obtained with the tooth contour models show good agreement with the results obtained with finite element models despite the limited number of elements. Increasing the number of elements in the model allows for modeling of armature reaction and increases the accuracy of the model.

This work can be continued with investigating the possibilities to model the armature reaction more accurately.

This paper proposes a modeling method which accurately describes the performance of a PMSM with limited number of elements. With this method, the calculation procedure can be easily used for optimization of the machine design.

The purpose of this paper is to propose the design concepts of external rotor switched flux hybrid magnet memory machine (SFHMMM) to further increase the torque capability while keeping the merits of internal rotor SFHMMM, such as adjustable back-EMF, and good flux weakening performance, etc.

The torque enhancing principle of external rotor SFHMMM, and the design considerations such as feasible stator and rotor pole numbers (N_s/N_r ) are discussed by equations. Then, the performances such as back-EMF, dq-axis inductances, torque and flux weakening performances are calculated and compared with the aid of finite element analysis software.

The external rotor SFHMMMs have obviously larger torque capabilities compared with the internal rotor ones under the same copper loss and machine size. The main reason is that the external SFHMMs could fully utilize the inner space of stator, which offers higher slot area, larger split ratio and consequently the higher average torque. For the external rotor machines with larger rotor pole number N_r , the back-EMF adjust ratio as well as the maxim torque are better. However, leakage flux and losses also increase with Nr due to limited machine size and higher operation frequency. Considering torque capability and flux weakening performance (efficiency map), the external SFHMMM with N_r =2N_s +1, e.g. 6/13 N_s/N_r stator/rotor pole machine, is the optimal choice.

This paper introduces the design concept and design considerations of external SFHMMM for the first time. The proposed machine could be a competent candidate for direct-drive electric vehicle applications.

The purpose of this work is to present a procedure for determining the wind drift factor through two-dimensional computational fluid dynamics (CFD) simulations of the wind acting on a wavy sea surface, such that the subjectivity of its estimation is reduced.

The wind drift factor was determined by two-dimensional CFD analyses with open-channel condition. The characteristic wave was determined by the Sverdrup–Munk–Bretschneider (SMB) method. The uncertainty analysis is based on convergence studies using a single parameter refinement (grid and time step).

This procedure allows the estimation of the wind drift factor in a fetch-limited domain. The domain's value in the analyzed region is 0.0519 ± 4.92% which is consistent with the upper values of the wind drift factors reported in the literature.

The use of a three-dimensional domain was impractical with the available computational resources because of the fine mesh required for wave modeling. The uncertainty analysis consisted only of a verification procedure. Validation against real data was not possible because of the lack of measured data in the analyzed region.

The wind drift factor is usually estimated based on either experience or random sampling. The original contribution of this work is the presentation of a CFD procedure for estimating the wind drift factor, in which the domain inlet is subjected to a wave boundary condition and to a wind velocity.