Tooth Windings Research Articles

ANALYTICAL CALCULATIONS OF ELECTROMAGNETIC QUANTITIES FOR SLOTTED BRUSHLESS MACHINES WITH SURFACE-INSET MAGNETS

In this paper, two-dimensional (2-D) analytical magnetic field calculations are used to compute crucial quantities of Brushless permanent-magnet (PM) machines with surface-inset PMs. The analytical magnetic field distribution is based on the subdomain technique in which the slotting and tooth-tip effects have been considered. It includes both different magnetization patterns (e.g., radial, parallel and Halbach) and different spatial distribution of winding (e.g., concentrated and distributed with one or more layers). The saturation effect of the magnetic circuit is neglected. In this investigation, the phase and line induced back electromotive force (EMF) waveforms, electromagnetic/cogging/reluctance torques, self-/mutual-inductances and unbalanced magnetic forces (UMFs) have been analytically calculated. The analytical expressions can be used for Brushless machines having surface-inset PMs with any radius-independent magnetization pattern. In this study, two slotted Brushless PM machines with surface-inset PMs have been selected to evaluate the efficacy of the analytical expressions by comparing the results with those obtained by the finite-element method (FEM). One of the case studies is a 9-slots/8-poles Brushless DC (BLDC) machine with radially magnetized PMs, non-overlapping all teeth wound winding and six-step rectangular armature current waveforms. The other is a 15-slots/4-poles Brushless AC (BLAC) machine with Halbach magnetization PMs, double-layer overlapping winding and sinusoidal armature current waveforms.

A Six-Phase 24-Slot/10-Pole Permanent-Magnet Machine With Low Space Harmonics for Electric Vehicle Applications

This paper proposes a six-phase surface-mounted permanent-magnet machine with a 24-slot/10-pole fractional slot winding, which not only eliminates the air-gap flux subharmonics, but also minimizes the effect of slot harmonics, which highly affect both the core and magnet losses. The six-phase winding design also offers an improved drive train availability for electric vehicle applications due to its inherent high fault-tolerant capability. When compared with a three-phase design, the proposed winding offers approximately 3.5% improvement in torque density, a significant reduction in both the core and magnet losses, and an improved overall efficiency. The proposed winding is deduced based on the stator shifting concept of two 12-slot/10-pole stators with single tooth windings. The coil span of the resulting machine will be two slots, which stands as a compromise between single tooth and distributed windings. The concept of stator shifting is first presented, and then, a prototype machine is designed and simulated using the 2-D finite-element analysis to validate the proposed concept. A comparative study is also carried out to compare six-phase and three-phase designs with the same slot/pole combination and also with the 18-slot/10-pole combination, which was recently shown to be a competitive alternative.

Thermal modeling and analysis of double-sided water-cooled permanent magnet linear synchronous machines

Purpose – With the popularization of permanent magnet linear synchronous machines (PMLSMs) in recent years, the temperature rise has attracted increasingly attention since excessive heat generated in the windings could deteriorate the electromagnetic performance. In order to solve this problem, adopting water-cooled system is an effective method. The purpose of this paper is to investigate a 12-slot/11-pole (12S/11P) water-cooled double-sided PMLSM, which adopts the all teeth wound concentrated winding and shifted armature ends. Design/methodology/approach – Based on 2D finite element analysis (FEA), the thermal performances, such as temperature distribution, the optimization of water flow rate and the influence of demagnetization, are investigated under the condition of continuous duty. Then the maximum current density and average thrust force are calculated for PMLSMs with or without water-cooled system. Finally, the detailed comparison is made between single-sided PMLSM and double-sided PMLSM. Findings – With water-cooled system, the thermal performance of PMLSM can be improved, such as an efficient decrease of temperature rise, restriction of permanent magnet demagnetization and a dramatic increase of the maximum thrust force. It is found that the water flow rate has a significant impact on temperature rise, which can be optimized according to demands. Originality/value – Electromagnetic and thermal coupled analysis is proposed in this paper. It can approximately predict thermal performance and save the manual iteration time at the same time. This method also can provide as a reference of thermal analysis for other PMLSMs.

3-D Numerical Hybrid Method for PM Eddy-Current Losses Calculation: Application to Axial-Flux PMSMs

This paper describes a 3-D numerical hybrid method (NHM) of the permanent-magnet (PM) eddy-current losses in axial-flux PM synchronous machines (PMSMs). The PM magnetic flux density is determined using the multi-static 3-D finite-element method (FEM) at resistance-limited (i.e., without eddy-current reaction field). Based on the predicted flux density distribution, the eddy-currents induced in the PMs and the 3-D PM eddy-current losses are calculated by 3-D finite-difference method (FDM) considering a large mesh. Therefore, this 3-D NHM is based on a coupling between the multi-static 3-D FEM and the 3-D FDM. Two 24-slots/16-poles (i.e., fractional-slot number) axial-flux PMSMs having a non-overlapping winding (all teeth wound type) with stator double-sided structure are studied: 1) surface-PM (SPM) and 2) interior-PM (IPM) To evaluate the reliability of the proposed technique, the 3-D PM eddy-current losses are determined and compared with transient 3-D FEM (i.e., magneto-dynamical 3-D FEM). The same nonlinear properties of the laminations have been applied for multi-static/transient 3-D FEM. The computation time can be divided by 25 with a difference less than 12%.

Design and Validation of a Synchronous Reluctance Motor With Single Tooth Windings

This paper presents for the first time the analysis and experimental validation of a six-slot four-pole synchronous reluctance motor with nonoverlapping fractional slot-concentrated windings. The machine exhibits high torque density and efficiency due to its high fill factor coils with very short end windings, facilitated by a segmented stator and bobbin winding of the coils. These advantages are coupled with its inherent robustness and low cost. The topology is presented as a logical step forward in advancing synchronous reluctance machines that have been universally wound with a sinusoidally distributed winding. The paper presents the motor design, performance evaluation through finite element studies and validation of the electromagnetic model, and thermal specification through empirical testing. It is shown that high performance synchronous reluctance motors can be constructed with single tooth wound coils, but considerations must be given regarding torque quality and the d-q axis inductances.

A novel fault tolerant permanent magnet synchronous motor with improved optimal torque control for aerospace application

Improving fault tolerant performance of permanent magnet synchronous motor has always been the central issue of the electrically supplied actuator for aerospace application. In this paper, a novel fault tolerant permanent magnet synchronous motor is proposed, which is characterized by two stators and two rotors on the same shaft with a circumferential displacement of mechanical angle of 4.5°. It helps to reduce the cogging torque. Each segment of the stator and the rotor can be considered as an 8-pole/10-slot five-phase permanent magnet synchronous motor with concentrated, single-layer and alternate teeth wound winding, which enhance the fault isolation capacity of the motor. Furthermore, the motor has high phase inductance to restrain the short-circuit current. In addition, an improved optimal torque control strategy is proposed to make the motor work well under the open-circuit fault and short-circuit fault conditions. Simulation and experiment results show that the proposed fault tolerant motor system has excellent fault tolerant capacity, which is able to operate continuously under the third open-circuit fault and second short-circuit fault condition without system performance degradation, which was not available earlier.

Proximity Losses in the Windings of High Speed Brushless Permanent Magnet AC Motors With Single Tooth Windings and Parallel Paths

Proximity and additional eddy-current losses can be difficult to calculate and if there are parallel paths then there can sometimes be increased losses which can be unexpected. The paper addresses these winding losses in a brushless permanent magnet machine with 18 slots, 16 poles and a spoke type rare earth magnet rotor. The winding has coils that are one pitch. Different simulation scenarios are investigated to illustrate the even when the windings are in slots they can still experience increased ac copper losses when rotating at high speed. High speed machines often have few series turns because of the high rate of change of flux linkage so they can have many parallel turns or strands in hand. Simulations are carried out at 12 000 r/min then some simulations are run at 4000 r/min for completeness. The simulations are run in a 2-D finite-element analysis environment.

Electric Machines with Non-Radially Mounted Rectangular Permanent Magnets / Elektriskās Mašīnas Ar Prizmatiskiem Neradiāli Novietotiem Pastāvīgajiem Magnētiem

The authors analyze the advantages and disadvantages of brushless synchronous electric machines with radially and non-radially mounted rectangular permanent magnets. The results show that the proposed nonradial mounting of permanent magnets considered in the paper, in several cases (e.g. multi-pole brushless generators with tooth windings of the armature) allows achievement of the following advantages: better technology of manufacturing the electric machine owing to simple packing of the stator winding in the stator open slots, which also increases the copper slot fillfactor; reduction in the mass-and-size of permanent magnets at least twice; significantly lower cost of the electric machine; and, finally, its greater specific power.

Analytical Magnetic Field Calculation of Slotted Brushless Permanent-Magnet Machines With Surface Inset Magnets

This paper presents an analytical magnetic field calculation for slotted brushless permanent-magnet (PM) machines equipped with surface inset magnets. The analytical expressions can be used to calculate both open-circuit and armature reaction field distributions. Although the expressions can be used for brushless PM machines with any magnetization pattern, the results of the open-circuit magnetic field are presented for three different magnetization patterns: radial, parallel, and Halbach. Different winding structures, such as overlapping, nonoverlapping with all teeth wound and nonoverlapping with alternate teeth wound, can be considered to compute the armature reaction field distribution. The analytical expressions can be used for the surface inset magnet structure with airspace between the magnets and the iron interpoles but they cannot be used in the case of brushless machines with surface mounted magnets. The calculations account for slotting and slot-opening effects via the subdomain technique. The analytical results for a four-pole, six-slot brushless PM machine with three magnetization patterns and nonoverlapping winding are presented and evaluated by comparing them with those obtained from the finite element method.

A Linear Stator Permanent Magnet Vernier HTS Machine for Wave Energy Conversion

In this paper, a new linear stator permanent magnet (PM) vernier high-temperature superconductor (HTS) machine is proposed for wave energy conversion. The machine adopts a double-sided design and inner-translator arrangement where the stator consists of two plane iron cores with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of the stator teeth. While the translator is designed as an iron core with salient teeth on the two sides, the HTS bulks are inset between every two adjacent salient teeth to shield the flux leakage, thus improving the power density of the machine. Based on using the finite element analysis, the characteristics and performances of the proposed machine are assessed. Also, the proposed machine is quantitatively compared with the existing linear stator PM vernier machine. Hence, it validates that its performance, especially the power density, can be improved significantly.

Design and Analysis of Linear Stator Permanent Magnet Vernier Machines

This paper presents a new class of linear permanent magnet (PM) vernier machines which is suitable for low speed and high thrust force applications. The machine is composed of a tubular stator and a tubular translator. The stator consists of an iron core with salient teeth wound with 3-phase armature windings and PMs mounted on the surface of stator teeth. The translator is designed as a simple tubular iron core with salient teeth so that it is very robust to transmit high thrust force. By using the finite element method, the characteristics and performances of the proposed machine are analyzed and verified.

The use of 90% Aloe vera freeze drying as the modulator of collagen density in extraction socket of incicivus Cavia cobaya

Wound healing is basically a complex process in which cellular and matrix act in concern to re-establish the integrity of injury tissues. This process can be simplified to be healing process consisted of haemostatic, inflammation, cell proliferation and tissue remodeling. The aimed of this research was to know the influence of freeze drying 90% Aloe vera application as mandible collagen density modulator in extraction socket of incisive Cavia cobaya. This research was done using Post Test Only Control Groups Design and Cavia cobaya as the sample. Six samples of each control group and 90% Aloe vera group applied to test each collagen density for three days and seven days. Then, the data was analyzed statistically using Mann Whitney with 5% significance rate. The result of the study indicates that administering 90% Aloe vera can accelerate the growth of collagen density in healing process of extraction socket. The conclusion is 90% Aloe vera can modulate the density of collageneous fiber in socket of extraction incicivus tooth wound of Cavia cobaya.

Multipole synchronous machines with fractional q < 1 tooth windings and excitation with permanent magnets

Specific features of multipole synchronous machines with fractional tooth windings and excitation with permanent magnets are considered. A comparison of such machines with motors with standard windings is given. Technical characteristics of manufactured motors are presented. Prospects for application of such motors are shown.

Direct-drive electromechanical steering booster for passenger cars

Results of the development of a direct-drive electromechanical steering booster (ESB) for a passenger car are considered. Technical characteristics of the ESB and the results of the calculations of characteristics and the simulation of the magnetic system are presented. Availability of application of magnetoelectric motors with fractional tooth windings in the ESB is shown.

Comparison of PM brushless motors, having either all teeth or alternate teeth wound

The electromagnetic performance of three-phase permanent magnet brushless motors in which the slot and pole numbers are similar and either all the teeth or only alternate teeth carry a concentrated coil is compared. Analytical and finite element techniques are employed to predict the air-gap flux density distribution, the cogging torque, electromotive force (EMF) and static torque waveforms, and the winding inductances, predicted results being validated by measurements. It is shown that there is a significant difference in both the phase and line EMF waveforms, the static torque-rotor position waveforms, and the self and mutual inductances.

The clinical diagnosis and treatment on eosinophitic granuloma of the jaws bone

目的 总结颌骨嗜酸细胞肉芽肿的临床诊断和治疗经验.方法对8例颌骨嗜酸细胞肉芽肿患者临床资料进行回顾性分析.结果颌骨嗜酸细胞肉芽肿男性多见,儿童易罹患,以下颌骨病变为多见.临床上对考虑囊肿、恶性肿瘤的患者,拔牙后创口经久不愈,牙龈溃疡而原因不明者均应考虑本病的可能.确诊仍依靠病理切片.结论本病局限型病损应作手术,多发性以及复发性病变应考虑综合治疗(手术加放疗及化疗).预后一般良好。

TOOTH WOUNDS AND THE INFECTED FIST

TOOTH WOUNDS AND THE INFECTED FIST

Studies on the Internal Gear Hobs : Hobs working like the broach and their cutting test

Before this paper, it is pointed out that the barrel shaped hob for generating the internal gears is difficult to make with theoretical exactness, and the conception of using a cylindrical forming hob instead of the generating one is reported. This forming hob has a tooth helix wound once and is made very easily. From the cutting test with the above hob made on trial, a new excellent hob is developed. Present paper describes the designing and manufacturing method of the new hob, the results of cutting test and the instructions for its practical use. This hob has the broach-like teeth wound twice along the helix, and can be made by almost the same technique as the one used in the manufacture of the ordinary hob. An accurate internal gear can be continuously cut with this hob, which will be especially suitable for large internal gear production.

A Summary of Reports and a Bacteriologic Study of Infections Caused by Human Tooth Wounds

A Summary of Reports and a Bacteriologic Study of Infections Caused by Human Tooth Wounds

A FATAL CASE OF BRAIN ABSCESS FROM VINCENT'S ANGINA FOLLOWING EXTRACTION OF A TOOTH UNDER PROCAINE HYDROCHLORIDE

A recent death following tooth extraction under local anesthesia, with isolation of the Vincent's organism from an abscess in the right temporal lobe of the brain, prompted a search of the literature for all information available regarding this disease. While Vincent's organisms have been found in connection with one case of acute leukemia, one case of pemphigus, hospital gangrene, pelvic peritonitis, industrial wounds, gunshot wounds, tooth wounds and two cases of brain abscess, its exact etiologic importance in all these conditions is not entirely clear. Little is known of the organisms. Some writers¹assert that the fusiform bacillus and the spirillum are different morphologic forms of the same organism; others believe they are not; and at least one student²of the disease believes that a short chain streptococcus is produced somewhere in the life span. It is certain, however, that Vincent's angina, or trench mouth, is prevalent, almost