Components Of Air-gap Flux Density Research Articles

A Novel Hybrid Excited Doubly Salient Machine With Asymmetric Stator Poles

A novel hybrid excited asymmetric stator pole doubly salient machine (HEASPDSM) is proposed in this paper. The new topologies and operational principle are first investigated by using a simplified equivalent magnetic circuit model. The harmonic components of air-gap flux density are then analyzed. The influence of key structural parameters of the proposed machine on the flux regulation ability and torque is studied. A full comparison on main electromagnetic performance indexes of the proposed 12/7 (stator/rotor poles) HEASPDSPM and several traditional doubly salient machines is presented. A prototype is fabricated and tested to validate the theoretical analysis. The results well demonstrate that the HEASPDSPM possesses various merits, such as strong flux regulation capability, high torque density, low cogging torque, and low torque ripple.

A Compact Expression for Cogging Torque Considering Both Radial and Tangential Fields for Surface-Mounted PM Motors

Cogging torque is due to the interaction between a magnet’s magnetomotive force and a slotted stator or rotor structure. In this paper, a compact equation for cogging torque is presented for surface-mounted permanent magnet motors. This equation has four terms of field interactions involving tangential and radial components of airgap flux density. These four terms are considered as sources of cogging. Variations of these sources with pole embrace are examined. In earlier publications, closed-form expressions for pole embrace corresponding to the minimum cogging were presented considering only radial fields. In this paper, an attempt is made to recognize the influence of tangential fields in cogging. The compact form given here distinctly reflects the significance of both radial and tangential field components. Furthermore, to study the trends of cogging sources with pole number and airgap radius, simplified expressions for harmonic content of field components are derived using the first-order binomial approximation. The analysis on cogging presented in this paper helps in determining search domains in which optimum embrace for minimum cogging can be found when both the radial and tangential field components are considered.

Analysis and optimization of a novel linear permanent Vernier motor

In this paper, a novel linear permanent magnet vernier (LPMV) motor is proposed. The advantages of the proposed motor are high force density, high efficiency, simple structure, and low cost. Firstly, the structure and the operation principle of the proposed motor which adopts 12-slots-11-pair-poles structure are descried. Based on the air-gap permeance function, the components of air-gap flux density is discussed. Secondly, the validation of LPMV is analyzed by finite element method (FEM), and the basic electromagnetic performance such as air-gap flux density, back-EMF, detent force and thrust waveform are analyzed in detail. Finally, the relationship between the thrust force characteristics and the design parameters are analyzed to provide useful information to the designers of LPMV.

Modeling and Analyzing of Magnetic Field of Segmented Halbach Array Permanent Magnet Machine Considering Gap Between Segments

The Halbach array permanent magnet machine has several advantages. Most notably, it has more sinusoidal air-gap flux density distribution, higher air-gap flux density amplitude, and self-shielding magnetization property. In engineering, the segmented Halbach array is usually used considering the complexity of fabrication, and certain gap exists between segments inevitably. To analyze the effect of the gap between segments on air-gap flux density, an analytical model of the Halbach array permanent magnet machine considering the gap between segments is established in this paper. The finite element model is adopted to validate the established analytical model. Furthermore, effects of the parameters of the segmented Halbach array, including gap between segments, segment number per pole, and pole pair number on the fundamental amplitude, and waveform distortion factor of the radial component of air-gap flux density are analyzed using the established analytical model.

Air-Gap Magnetic Field Analysis of Wind Generator With PM Embedded Salient Poles by Analytical and Finite Element Combination Technique

A combined analytical and FEM technique is proposed for predicting the air-gap magnetic field distribution of a PM embedded salient pole wind generator. The influence of slotting on both radial and circumferential components of air-gap flux density is taken into account. By employing the proposed combination technique, the magnetic field distributions when the stator and rotor are at different relative positions can be calculated much faster than that by FEM. Based on the magnetic field distributions, the cogging torques are predicted and verified by the FEM, while the relationship between cogging torque and design parameters are further investigated. The proposed combination technique provides an efficient and accurate prediction method for the air-gap magnetic field distribution of large electrical machines with a complex PM pole structure.

Finite-Element Analysis of Field Distribution and Characteristic Performance of Squirrel-Cage Induction Motor With Broken Bars

This paper develops the foundations of a technique for diagnosis and characterization of effects of broken bars in squirrel-cage induction motors based on the time-stepping coupled finite-element approach. These studies are performed by using the model to compute healthy case, one-broken-bar fault, and two adjacent broken bars fault performance data, which contains stator starting current waveforms, the current density on the bars, the magnetic force distribution on the rotor bars, and the distribution of magnetic field. Meanwhile, the iron core loss distributions on the rotor tooth adjacent to broken bars are computed, and the harmonic component of air-gap flux density is analyzed. From this data, the faulty signatures are extracted. Theoretical approach together with experimental results derived from a two-pole 1.1 kW induction motor confirms the validity of the proposed method. Furthermore, this method, which could help to develop diagnostics of broken bars and performance evaluation of induction motors, has great potential in future applications

On-Load Saturation Characteristics of a Synchronous Generator Based on Magnetic Flux.

Magnetic flux in a synchronous generator is saturated by an iron core in magnetic path. Conventionally, saturation characteristics of generator are examined in the case of no-load saturation test and zero power factor test. In these cases, the path of magnetic flux is limitted in d-axis direction. Therefore the saturation characteristics are grasped by measurements of terminal voltages and currents with regarding a generator as a black box. On the other hand, an on-load saturation characteristics have never been discussed in experiment. However, the conventional treatment of saturation characteristics are considered to be reasonable in physical meaning, because the analysis based on conventional assumptions does not contradict their experimental results. In this paper, the on-load saturation characteristics are discussed experimentally based on the experimental results at a generator operating onto an infinite bus system. As results, the harmonic components of air-gap flux density depend only upon the shape of salient rotor at no-load state. As for the tested generator, the saturation characteristics of d-axis component are independent of q-axis component in despite of the existence of q-axis current. Moreover, the on-load saturation characteristics for d-axis current corresponds to the shifted curve of the no-load saturation characteristics by a constant flux components with taking the ratio of field and d-axis current in consideration.