Influence of Frequency on Electromagnetic Field of Super High-Speed Permanent Magnet Generator

Hongbo Qiu,Yanqi Wei,Wei Wang,Bingxia Tang,Xifang Zhao,Cunxiang Yang 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

When compared with traditional power frequency generators, the frequency of a super high-speed permanent magnet generator(SHSPMG) is a lot higher. In order to study the influence of frequency on the electromagnetic field of SHSPMGs, a 60000rpm,117kW SHSPMG was taken as a research object. The two-dimensional finite element model of the generator was established,and the two-dimensional transient field of the generator was simulated. In addition, a test platform of the generator was set upand tested. The reliability of the simulation was verified by comparing the experiment data with that of the simulation. Then thegenerator electromagnetic field under different frequencies was studied, and the influence mechanism of frequency on thegenerator electromagnetic field was revealed. The generator loss, voltage regulation rate, torque and torque ripple were analyzedunder the rated active power load and different frequencies. The influences of frequency on the eddy current density, loss, voltageregulation rate and torque ripple of the generator were obtained. These conclusions can provide some reference for the designand optimization of SHSPMGs.

Research on the Influence of Inter-turn Short Circuit Fault on the Temperature Field of Permanent Magnet Synchronous Motor

Hongbo Qiu,Wenfei Yu,Bingxia Tang,Cunxiang Yang,Haiyang Zhao 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4

When the inter-turn short circuit (ITSC) fault occurs, the distortion of the magnetic field is serious. The motor loss variations of each part are obvious, and the motor temperature field is also affected. In order to obtain the influence of the ITSC fault on the motor temperature distribution, firstly, the normal and the fault finite element models of the permanent magnet synchronous motor (PMSM) were established. The magnetic density distribution and the eddy current density distribution were analyzed, and the mechanism of loss change was revealed. The effects of different forms and degrees of the fault on the loss were obtained. Based on the loss analysis, the motor temperature field calculation model was established, and the motor temperature change considering the loop current was analyzed. The influence of the fault on the motor temperature distribution was revealed. The sensitivity factors that limit the motor continuous operation were obtained. Finally, the correctness of the simulation was verified by experiments. The conclusions obtained are of great significance for the fault and high temperature demagnetization of the permanent magnet analysis.

Research on the Influences of Time Harmonics on Permanent Magnet Synchronous Motors with Hybrid Magnet Poles

Hongbo Qiu,Yuedong Guo,Wenfei Yu,Bingxia Tang,Cunxiang Yang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3

With the development of electric electron technology and controlling technology, controller for driving permanent magnet synchronous motors is used widely. The using of a controller can expand the motor speed range and improve motor runtime performances. However, the output current of a controller contains lots of time harmonics that will have bad infl uences on motor torque and losses. In order to analyze the infl uences of the time harmonics on the motor performances, diff erent time harmonic currents were injected into the motor armature. Taking a 750 W, 250 r/min permanent magnet synchronous motor with hybrid magnet poles (HPPMSM) as an example, the 2-D fi nite model was established. On this basis, the torque ripple and eddy current losses of permanent magnets with diff erent time harmonics were obtained. The infl uences of time harmonics on motor torque ripple and eddy current losses were determined, and the impacting mechanism was revealed. The analyses may be helpful for the optimal design of HPPMSM.

Correction to: Research on the Infl uences of Time Harmonics on Permanent Magnet Synchronous Motors with Hybrid Magnet Poles

Hongbo Qiu,Yuedong Guo,Wenfei Yu,Bingxia Tang,Cunxiang Yang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.4

Influence of Frequency on Electromagnetic Field of Super High-Speed Permanent Magnet Generator

Qiu, Hongbo,Wei, Yanqi,Wang, Wei,Tang, Bingxia,Zhao, Xifang,Yang, Cunxiang The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

When compared with traditional power frequency generators, the frequency of a super high-speed permanent magnet generator (SHSPMG) is a lot higher. In order to study the influence of frequency on the electromagnetic field of SHSPMGs, a 60000rpm, 117kW SHSPMG was taken as a research object. The two-dimensional finite element model of the generator was established, and the two-dimensional transient field of the generator was simulated. In addition, a test platform of the generator was set up and tested. The reliability of the simulation was verified by comparing the experiment data with that of the simulation. Then the generator electromagnetic field under different frequencies was studied, and the influence mechanism of frequency on the generator electromagnetic field was revealed. The generator loss, voltage regulation rate, torque and torque ripple were analyzed under the rated active power load and different frequencies. The influences of frequency on the eddy current density, loss, voltage regulation rate and torque ripple of the generator were obtained. These conclusions can provide some reference for the design and optimization of SHSPMGs.

Research on the Influence of Inter-turn Short Circuit Fault on the Temperature Field of Permanent Magnet Synchronous Motor

Qiu, Hongbo,Yu, Wenfei,Tang, Bingxia,Yang, Cunxiang,Zhao, Haiyang The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.8 No.1

When the inter-turn short circuit (ITSC) fault occurs, the distortion of the magnetic field is serious. The motor loss variations of each part are obvious, and the motor temperature field is also affected. In order to obtain the influence of the ITSC fault on the motor temperature distribution, firstly, the normal and the fault finite element models of the permanent magnet synchronous motor (PMSM) were established. The magnetic density distribution and the eddy current density distribution were analyzed, and the mechanism of loss change was revealed. The effects of different forms and degrees of the fault on the loss were obtained. Based on the loss analysis, the motor temperature field calculation model was established, and the motor temperature change considering the loop current was analyzed. The influence of the fault on the motor temperature distribution was revealed. The sensitivity factors that limit the motor continuous operation were obtained. Finally, the correctness of the simulation was verified by experiments. The conclusions obtained are of great significance for the fault and high temperature demagnetization of the permanent magnet analysis.

Mechanical Properties of High Mg-Content Al-Mg-Sc-Zr Alloy Fabricated by Selective Laser Melting

Hao Tang,Yaoxiang Geng,Jinjie Luo,Junhua Xu,Hongbo Ju,Lihua Yu 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

The efects of process parameters and aging treatment on the microstructure and mechanical properties of selective lasermelting (SLM) fabricated high Mg-content Al-Mg-Sc-Zr aluminum alloy were systematically studied. Our experiment resultsshow that the samples exhibit good processability with porosity less than 1%. The increase of Mg content in Al-Mg-Sc-Zris benefcial to reduce the texture of the alloy. The laser scanning speed has a large infuence on the Vickers hardness ofas-fabricated samples. The maximum microhardness of as-fabricated sample reaches 148±2 HV with a compression yieldstrength of 342±7 MPa. After aging treatment, the distinction in microhardness of the samples obtained under diferent laserscanning speed is obviously reduced, and the mechanical properties of the samples are further improved with a maximummicrohardness of 175±5 HV and a maximum compressive yield strength of 476±10 MPa, which are superior to the knownAl-Mg-Sc-Zr alloy with same Sc and Zr content fabricated by SLM. In this study, a novel high Mg-content Al-Mg-Sc-Zraluminum alloy specifcally for SLM with good processability and mechanical properties was reported.

A Privacy-preserving and Energy-efficient Offloading Algorithm based on Lyapunov Optimization

Lu Chen,Hongbo Tang,Yu Zhao,Wei You,Kai Wang 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.8

In Mobile Edge Computing (MEC), attackers can speculate and mine sensitive user information by eavesdropping wireless channel status and offloading usage pattern, leading to user privacy leakage. To solve this problem, this paper proposes a Privacy-preserving and Energy-efficient Offloading Algorithm (PEOA) based on Lyapunov optimization. In this method, a continuous Markov process offloading model with a buffer queue strategy is built first. Then the amount of privacy of offloading usage pattern in wireless channel is defined. Finally, by introducing the Lyapunov optimization, the problem of minimum average energy consumption in continuous state transition process with privacy constraints in the infinite time domain is transformed into the minimum value problem of each timeslot, which reduces the complexity of algorithms and helps obtain the optimal solution while maintaining low energy consumption. The experimental results show that, compared with other methods, PEOA can maintain the amount of privacy accumulation in the system near zero, while sustaining low average energy consumption costs. This makes it difficult for attackers to infer sensitive user information through offloading usage patterns, thus effectively protecting user privacy and safety.

The Influence of Family Function on Occupational Attitude of Chinese Nursing Students in the Probation Period: The Moderation Effect of Social Support

Li, Rui,Tang, Ruizhi,Li, Zijia,Jiang, Hongbo,Liu, Xin,Wang, Wei 한국간호과학회 2021 Journal of Korean Academy of Nursing Vol.51 No.6

Purpose: The purpose of this study was to explore the factors influencing the occupational attitudes of nursing students in the probation period. Methods: Nursing students in the probation period from five hospitals completed an anonymous survey. The instruments included the nursing occupational attitude scale, family adaptability, partnership, growth, affection, and resolve index, and perceived social support scale. The study examined the moderation model between family function, perceived social support, and occupational attitudes using PROCESS 3.2. Results: For nursing students, when social support was low, family function had a significant positive impact on occupational attitudes and intentions, and the effect was much higher than that of perceived social support. Conclusion: Family function has a significant positive explanatory effect on attitude and intention (β = .13, p < .001 and β = .12, p < .001); the interaction term between family function and perceived social support are significant (β = .01, p < .001 and β = .01, p < .001). Perceived social support has a significant moderating effect on the relationship between family function and occupational attitudes of nursing students in the probation period. Family function has a significant difference in the occupational attitudes and intentions of nursing students with low perceived social support. Nursing students perceive social support in the probation period has a significant moderation effect in the relationship between their family function and occupational attitudes. Interns with low family function should be given more social support to improve their occupational attitudes.

Traffic Forecast Assisted Adaptive VNF Dynamic Scaling

Hang Qiu,Hongbo Tang,Yu Zhao,Wei You,Xinsheng Ji 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.11

NFV realizes flexible and rapid software deployment and management of network functions in the cloud network, and provides network services in the form of chained virtual network functions (VNFs). However, using VNFs to provide quality guaranteed services is still a challenge because of the inherent difficulty in intelligently scaling VNFs to handle traffic fluctuations. Most existing works scale VNFs with fixed-capacity instances, that is they take instances of the same size and determine a suitable deployment location without considering the cloud network resource distribution. This paper proposes a traffic forecasted assisted proactive VNF scaling approach, and it adopts the instance capacity adaptive to the node resource. We first model the VNF scaling as integer quadratic programming and then propose a proactive adaptive VNF scaling (PAVS) approach. The approach employs an efficient traffic forecasting method based on LSTM to predict the upcoming traffic demands. With the obtained traffic demands, we design a resource-aware new VNF instance deployment algorithm to scale out under-provisioning VNFs and a redundant VNF instance management mechanism to scale in over-provisioning VNFs. Trace-driven simulation demonstrates that our proposed approach can respond to traffic fluctuation in advance and reduce the total cost significantly.