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454 results on '"Chen, J.T."'

37. Influence of the rotor pole number on optimal parameters in flux-switching PM brushless AC machines by the lumped-parameter magnetic circuit model

Author

Chen, J.T. and Zhu, Z.Q.

Subjects
Brushless electric motors -- Design and construction, Brushless electric motors -- Properties, Alternating current electric motors -- Design and construction, Alternating current electric motors -- Properties, Rotors -- Identification and classification, Rotors -- Influence, Rotors -- Research, Magnets, Permanent -- Magnetic properties, Magnetic circuits -- Models, Electric motor industry -- Product development, Business, Computers, Electronics, Electronics and electrical industries
Published
2010

41. Cogging torque in flux-switching permanent magnet machines

Author

Zhu, Z.Q., Thomas, A.S., Chen, J.T., and Jewell, G.W.

Subjects
Magnets, Permanent -- Analysis, Machinery -- Analysis, Magneto-electric machines -- Analysis, Business, Electronics, Electronics and electrical industries
Published
2009

42. Influence of skew and cross-coupling on flux-weakening performance of permanent-magnet brushless ac machines

Author

Qi, G., Chen, J.T., Zhu, Z.Q., Howe, D., Zhou, L.B., and Gu, C.L.

Subjects
Magnets, Permanent -- Properties, Magnets, Permanent -- Usage, Magnetic flux -- Research, Induction, Electromagnetic -- Research, Finite element method -- Usage, Electrical machinery -- Alternating current, Electrical machinery -- Properties, Electrical machinery -- Usage, Business, Electronics, Electronics and electrical industries
Abstract

A method is proposed for predicting the flux-weakening performance of permanent-magnet (PM) brushless ac machines accounting for skew and d-q axis cross-coupling. The method is based on a d-q-axis flux-linkage model, a hybrid 2-D finite-element (FE)--analytical method being used to predict the d-and q-axis inductances. However, it only requires 2-D FE analysis of the magnetic field distribution over a cross section of the machine. The developed method is used to predict the torque-speed characteristic of an interior PM brushless ac machine with one stator slot-pitch skew. This is compared with predictions from a direct FE analysis of the machine and validated by measurements. Index Terms--Cross-coupling, flux-weakening, inductances, magnetic saturation, optimal control, permanent-magnet machine, skew.

Published
2009

44. Stator and rotor pole combinations for multi-tooth flux-switching permanent-magnet brushless AC machines

Author

Chen, J.T., Zhu, Z.Q., and Howe, D.

Subjects
Magnets, Permanent -- Usage, Brushless electric motors -- Design and construction, Torque -- Evaluation, Mathematical optimization, Business, Electronics, Electronics and electrical industries
Abstract

A simple analytical method is developed for determining the optimal combination of stator pole and rotor pole numbers for a multi-tooth flux-switching permanent magnet (FSPM) machine, and the optimal design of the stator teeth for maximum torque. In addition, the rotor pole width and the split ratio are optimized by finite element analysis. The optimized multi-tooth FSPM machine exhibits a significantly higher torque capability and requires a significantly lower volume of magnet material than a conventional FSPM machine. The performance of the proposed multi-tooth FSPM machine is validated experimentally. Index Terms--Multi-tooth, permanent magnet, flux-switching, brushless, direct-drive.

Published
2008

45. Analysis of a novel multi-tooth flux-switching PM brushless ac machine for high torque direct-drive applications

Author

Zhu, Z.Q., Chen, J.T., Pang, Y., Howe, D., Iwasaki, S., and Deodhar, R.

Subjects
Brushless electric motors -- Magnetic properties, Brushless electric motors -- Electric properties, Brushless electric motors -- Analysis, Torque -- Analysis, Electrical machinery -- Alternating current, Electrical machinery -- Magnetic properties, Electrical machinery -- Electric properties, Electrical machinery -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

A three-phase, multi-tooth flux-switching permanent magnet brushless ac machine is analyzed, its electromagnetic performance, viz., the phase flux-linkage and back-EMF waveforms, the self- and mutual-inductances, the cogging torque, the electromagnetic torque, and the torque-current characteristic, are predicted by 2-D and 3-D finite-element analyses and validated experimentally. Compared with a conventional flux-switching machine, a multi-tooth machine requires a significantly smaller volume of magnet material, since only half the number of permanent magnets is required, and it exhibits a higher torque density at low excitation currents as well as a lower torque ripple. However, since it saturates more quickly as the current is increased due to the higher armature reaction, and at very high electric loadings its torque capability is lower than that of a conventional flux-switching machine. Index Terms--Brushless, direct-drive, flux-switching, multi-tooth, permanent magnet.

Published
2008

46. Influence of stator asymmetry on cogging torque of permanent magnet brushless machines

Author

Zhu, Z.Q., Chen, J.T., Wu, L.J., and Howe, D.

Subjects
Torque -- Analysis, Magnets, Permanent -- Magnetic properties, Magnets, Permanent -- Analysis, Business, Electronics, Electronics and electrical industries
Abstract

The paper investigates the influence of stator asymmetry on the cogging torque of permanent magnet brushless motors. It shows that high localized magnetic saturation due to such asymmetry can significantly increase the magnitude of the cogging torque and introduces cogging components which have an order lower than the least common multiple between the stator slot number and the rotor pole number. The findings are confirmed by both finite element analyses and measurements on an 18-slot, 6-pole prototype motor. Index Terms--Asymmetry, brushless machines, cogging torque, permanent magnet.

Published
2008

47. A multinational, multicentre study on the psychological outcomes and associated physical symptoms amongst healthcare workers during COVID-19 outbreak

Author

Chew, N.W.S. Lee, G.K.H. Tan, B.Y.Q. Jing, M. Goh, Y. Ngiam, N.J.H. Yeo, L.L.L. Ahmad, A. Ahmed Khan, F. Napolean Shanmugam, G. Sharma, A.K. Komalkumar, R.N. Meenakshi, P.V. Shah, K. Patel, B. Chan, B.P.L. Sunny, S. Chandra, B. Ong, J.J.Y. Paliwal, P.R. Wong, L.Y.H. Sagayanathan, R. Chen, J.T. Ying Ng, A.Y. Teoh, H.L. Tsivgoulis, G. Ho, C.S. Ho, R.C. Sharma, V.K.

Abstract

Objective: Since the declaration of the coronavirus 2019 (COVID-19) outbreak as pandemic, there are reports on the increased prevalence of physical symptoms observed in the general population. We investigated the association between psychological outcomes and physical symptoms among healthcare workers. Methods: Healthcare workers from 5 major hospitals, involved in the care for COVID-19 patients, in Singapore and India were invited to participate in a study by performing a self-administered questionnaire within the period of February 19 to April 17, 2020. Healthcare workers included doctors, nurses, allied healthcare workers, administrators, clerical staff and maintenance workers. This questionnaire collected information on demographics, medical history, symptom prevalence in the past month, Depression Anxiety Stress Scales (DASS-21) and the Impact of Events Scale-Revised (IES-R) instrument. The prevalence of physical symptoms displayed by healthcare workers and the associations between physical symptoms and psychological outcomes of depression, anxiety, stress, and post-traumatic stress disorder (PTSD) were evaluated. Results: Out of the 906 healthcare workers who participated in the survey, 48 (5.3%) screened positive for moderate to very-severe depression, 79 (8.7%) for moderate to extremely-severe anxiety, 20 (2.2%) for moderate to extremely-severe stress, and 34 (3.8%) for moderate to severe levels of psychological distress. The commonest reported symptom was headache (32.3%), with a large number of participants (33.4%) reporting more than four symptoms. Participants who had experienced symptoms in the preceding month were more likely to be older, have pre-existing comorbidities and a positive screen for depression, anxiety, stress, and PTSD. After adjusting for age, gender and comorbidities, it was found that depression (OR 2.79, 95% CI 1.54–5.07, p = 0.001), anxiety (OR 2.18, 95% CI 1.36–3.48, p = 0.001), stress (OR 3.06, 95% CI 1.27–7.41, p = 0.13), and PTSD (OR 2.20, 95% CI 1.12–4.35, p = 0.023) remained significantly associated with the presence of physical symptoms experienced in the preceding month. Linear regression revealed that the presence of physical symptoms was associated with higher mean scores in the IES-R, DASS Anxiety, Stress and Depression subscales. Conclusions: Our study demonstrates a significant association between the prevalence of physical symptoms and psychological outcomes among healthcare workers during the COVID-19 outbreak. We postulate that this association may be bi-directional, and that timely psychological interventions for healthcare workers with physical symptoms should be considered once an infection has been excluded. © 2020 Elsevier Inc.

Published
2020

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