Calculation of Electromagnetic Excitation Forces in Double Skewed Motors

Xiaohua Bao,Chong Di,Yang Zhou 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

An electromagnetic excitation force is caused by the air-gap flux density, which greatly influences the noise and vibration of the motor. In many real projects, skewed slot technology is widely used to reduce the harmonic components of the air-gap flux density to reduce the noise and vibration of the motor. However, a skewed slot has several side effects such as a transverse current and axial drifting. Thus, a double skewed slot rotor is selected with the aim of eliminating these side effects. This paper presents the exact structure of the double skewed slot rotor and the mechanism whereby the electromagnetic excitation force can be reduced. A multi-slice method is adopted to model the special structure. Finite element simulation is used to verify the theory.

Parameter Optimal Choice of Claw Pole Alternator based on Iron Loss Model

Bao, Xiaohua,Wei, Qiong,Wu, Feng,Li, Jiaqing Journal of International Conference on Electrical 2013 Journal of international Conference on Electrical Vol.2 No.3

Based on classical Berotti discrete iron loss calculation model, the iron loss analysis mathematical model of alternator was proposed in this paper. Considering characteristics of high speed and changing frequency of the alternator, Maxwell 3-D model was built to analyze iron loss corresponding to each running speed in alternator. Based on iron loss model of alternator at rated speed, the rotor claw pole size was made an optimization design. The optimization results showed that alternator's output performance had been improved. A new idea was explored in size optimization design of claw pole alternator.

Analysis of Slot Leakage Reactance of Submersible Motor with Closed Slots during Starting Transient Operation

Xiaohua Bao,Chong Di,Yong Fang 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.1

Generally, closed slots are adopted to reduce the water friction loss in both the stator and the rotor of water filling submersible motor due to the special environment of operation. One of the obvious differences between the traditional induction motors and water filling submersible motors is that the submersible motors only need relatively smaller starting torque. This paper aims to analyze the slot leakage reactance of water filling submersible motor during starting transient operation. An improved analytical method which considered the magnetic saturation of the slot bridge and the skin effect of rotor bars is proposed. The slot permeance factor which has a direct impact on the slot leakage reactance is calculated. Then finite element models with different stator slot types are constructed and search coils are introduced to measure the slot flux linkage. Moreover, the starting performances of the models with two typical stator slots are compared and the flux leakage characteristics are obtained. Finally, the results obtained by finite element method are very close to the results obtained by analytical method.

Calculation of Electromagnetic Excitation Forces in Double Skewed Motors

Bao, Xiaohua,Di, Chong,Zhou, Yang The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.2

An electromagnetic excitation force is caused by the air-gap flux density, which greatly influences the noise and vibration of the motor. In many real projects, skewed slot technology is widely used to reduce the harmonic components of the air-gap flux density to reduce the noise and vibration of the motor. However, a skewed slot has several side effects such as a transverse current and axial drifting. Thus, a double skewed slot rotor is selected with the aim of eliminating these side effects. This paper presents the exact structure of the double skewed slot rotor and the mechanism whereby the electromagnetic excitation force can be reduced. A multi-slice method is adopted to model the special structure. Finite element simulation is used to verify the theory.

Analysis of Slot Leakage Reactance of Submersible Motor with Closed Slots during Starting Transient Operation

Bao, Xiaohua,Di, Chong,Fang, Yong The Korean Institute of Electrical Engineers 2016 Journal of Electrical Engineering & Technology Vol.11 No.1

Generally, closed slots are adopted to reduce the water friction loss in both the stator and the rotor of water filling submersible motor due to the special environment of operation. One of the obvious differences between the traditional induction motors and water filling submersible motors is that the submersible motors only need relatively smaller starting torque. This paper aims to analyze the slot leakage reactance of water filling submersible motor during starting transient operation. An improved analytical method which considered the magnetic saturation of the slot bridge and the skin effect of rotor bars is proposed. The slot permeance factor which has a direct impact on the slot leakage reactance is calculated. Then finite element models with different stator slot types are constructed and search coils are introduced to measure the slot flux linkage. Moreover, the starting performances of the models with two typical stator slots are compared and the flux leakage characteristics are obtained. Finally, the results obtained by finite element method are very close to the results obtained by analytical method.

2D FEM Based Fast Approach to Predict Electromagnetic Performances of a Variable-Speed FMaSynRM Considering Skewing Effects

Di Chong,Bao Xiaohua,Jiang Wei,Xie Bao 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.1

Skewing techniques have been widely used in the feld of the design of diferent types of electrical machines, because it can help to reduce the torque ripple, mitigate the electromagnetic noise and vibration, etc. To model the skewing efects in the electrical machine design accurately, the fnite element method is appreciated in both the academia and industry. To achieve a fast modelling of skewing efects, a novel 2D based approach to estimate the electromagnetic performances in the whole speed range for variable-speed electrical machines has been proposed in this paper, which is further improved from the traditional multi-slice method. Firstly, a series of simulations at diferent loads will be run to get the electromagnetic performances for the variable-speed machines. Secondly, based on the multi-slice method, the performance on diferent slices can be predicted from the results obtained from the existing simulations by coordinate transform and interpolation directly and no more extra simulations are needed. Thirdly, taking a ferrite magnet assisted synchronous reluctance machine (FMaSynRM) with skewing as an example, the electromagnetic performances including electromagnetic torque, stator current and voltage, efciency map are compared in detail by both the proposed method and experiments.

Inductances Evaluation of a Squirrel-Cage Induction Motor with Curved Dynamic Eccentricity

Qiang Lv,Xiaohua Bao,Yigang He,Yong Fang,Xiaowei Cheng 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5

Eccentricity faults more or less exist in all rotating electrical machines. This paper establishes a more precise model of dynamic eccentricity (DE) in electrical machines named as curved dynamic eccentricity. It is a kind of axial unequal eccentricity which has not been investigated in detail so far but occurs in large electrical machines. The inductances of a large three-phase squirrel-cage induction machine (SCIM) under different levels of curved DE conditions are evaluated using winding function approach (WFA). These inductances include the stator self and mutual inductances, rotor self and mutual inductances, and mutual inductances between stator phases and rotor loops. A comparison is made between the calculation results under curved DE and the corresponding pure DE conditions. It indicates that the eccentricity condition will be more terrible than the monitored eccentricity based on the conventional pure DE model.

A Novel Semi-inserted Dual-stator Low-speed High-torque Permanent Magnet Drive Motor

Jiwei Liu,Xiaohua Bao,Youyuan Ni,Mingji Zou Korean Magnetics Society 2018 Journal of Magnetics Vol.23 No.4

Low-speed high-torque permanent magnet direct drive machine (LSPMDM) overcomes the shortcomings of traditional drive system, but its volume is large. In this paper, the numerical relationship between the motor external diameter and the rated speed is deduced, and improvement of the torque density is qualitatively analyzed for a dual-stator motor. Owing to that semi-inserted magnetic circuit structure and auxiliary slots under the poles can further increase the torque density of the motor, the effect of the shape, number and position of the auxiliary slots on the salient pole rate is also studied through comparative analysis. By incorporating the merits of dual-stator motor and semi-inserted magnetic circuit structure with the auxiliary slots, a novel motor topology is proposed, which is verified by finite element analysis with good performance.

Influence of Thermal Expansion on Eccentricity and Critical Speed in Dry Submersible Induction Motors

Lv, Qiang,Bao, Xiaohua,He, Yigang The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.1

Rotor eccentricity is one of the major factors that directly influence the security of horizontal electrical machines, and the critical speed of the shaft has a close relationship with vibration. This paper deals with the influence of thermal expansion on the rotor eccentricity and critical speed in large dry submersible motors. The dynamic eccentricity (where the rotor is still turning around the stator bore centre but not its own centre) and critical speed of a three-phase squirrel-cage submersible induction motor are calculated via hybrid analytical/finite element method. Then the influence of thermal expansion is investigated by simulation. It is predicted from the study that the thermal expansion of the rotor and stator gives rise to a significant air-gap length decrement and an inconspicuous slower critical speed. The results show that the thermal expansion should be considered as an impact factor when designing the air gap length.

Novel Rotor Winding Investigation for Reduction of Torque Pulsation and Electromagnetic Noise in Squirrel Cage Induction Motor

Yang Zhou,Xiaohua Bao,Wuhua Jiang,Jiwei Liu,Wei Xu 한국자기학회 2019 Journal of Magnetics Vol.24 No.1

In the design of squirrel-cage induction machines, torque pulsation and electromagnetic noise always exist. However, they cannot be minimized simultaneously with no matter which slot combination. Electromagnetic noise is aroused by the spatial harmonics in the air gap which are generated by stator magneto-motive force and rotor magneto-motive force. Generally, stator slot number cannot be changed while rotor slot number and slot size could be modified optionally. One set of uniform-bar rotor winding cannot solve this problem. To investigate this issue, this paper proposes a novel rotor winding connection topology for the simultaneous reduction of torque pulsation and electromagnetic noise. 2D finite element models with conventional rotor winding and novel rotor winding are simulated and compared.