Fault tolerant motor drive system with redundancy for critical applications

Some of the recent research activities in the area of electric motor drives for critical applications (such as aerospace and nuclear power plants) are focused on looking at various motor and drive topologies. This paper presents a motor drive system, which provides an inverter topology for three-phase motors, and also proposes an increased redundancy. The paper develops a simulation model for the complete drive system including synthetic faults. In addition, the hardware details including the implementation of DSP based motor controller, inverter module, and brushless PM motor system are provided and some experimental results are presented.N. Ertugrul, W. Soong, G. Dostal and D. Saxo

Analysis and design of energy storage for current-source 1-ph Grid-connected PV inverters

Copyright © 2008 IEEEThis paper examines the analysis and design of a DC link inductor for a current source 1-ph grid-connected photovoltaic (PV) inverter. Firstly the effect of voltage or current ripple on the PV array average output power is examined using a normalized PV output characteristic. Secondly the design of the inductor and in particular the trade-off between the PV array output power loss and the inductor copper loss are discussed. An inductor was built and a comparison of the calculated and measured loss breakdown is presented.G. Ertasgin, D.M. Whaley, N. Ertugrul and W.L. Soon

Analysis and performance evaluation of an axial-field brushless PM machine utilising soft magnetic composites

Copyright © 2007 IEEEOne of the major research activities in electric machines involves the use of alternative magnetic materials. Soft magnetic composites (SMC) offer the advantages of 3D magnetic flux paths and low-cost manufacturing. This paper examines the analysis and modelling of a prototype axial-field permanent magnet machine which uses SMC. Measured parameters and performance with an inverter is compared to 3D finite-element simulations. © 2007 IEEE

Investigation of inverterless control of interior permanent-magnet alternators

Copyright © 2006 IEEEThis paper investigates the performance and control of a low-cost 6-kW concept demonstrator of an "inverterless" automotive alternator. This is based on a switched-mode rectifier (SMR) combined with a high-flux interior permanent-magnet (PM) machine. Duty cycle control of the SMR is described and the theoretical predictions are compared with open-loop experimental results. The efficiency of the concept demonstrator is examined as a function of speed and load. Control issues regarding automotive operation are discussed.Chong-Zhi Liaw, David M. Whaley, Wen L. Soong and Nesimi Ertugru

Validating a methodology to measure frailty syndromes at hospital level utilising administrative data.

BACKGROUND: Identifying older people with clinical frailty, reliably and at scale, is a research priority. We measured frailty in older people using a novel methodology coding frailty syndromes on routinely collected administrative data, developed on a national English secondary care population, and explored its performance of predicting inpatient mortality and long length of stay at a single acute hospital. METHODOLOGY: We included patient spells from Secondary User Service (SUS) data for those ≥65 years with attendance to the emergency department or admission to West Middlesex University Hospital between 01 July 2016 to 01 July 2017. We created eight groups of frailty syndromes using diagnostic coding groups. We used descriptive statistics and logistic regression to explore performance of diagnostic coding groups for the above outcomes. RESULTS: We included 17,199 patient episodes in the analysis. There was at least one frailty syndrome present in 7,004 (40.7%) patient episodes. The resultant model had moderate discrimination for inpatient mortality (area under the receiver operating characteristic curve (AUC) 0.74; 95% confidence interval (CI) 0.72-0.76) and upper quartile length of stay (AUC 0.731; 95% CI 0.722-0.741). There was good negative predictive value for inpatient mortality (98.1%). CONCLUSIONS: Coded frailty syndromes significantly predict outcomes. Model diagnostics suggest the model could be used for screening of elderly patients to optimise their care

Intuitive Tools for the Design and Analysis of Communication Payloads for Satellites

In an effort to make future communications satellite payload design more efficient and accessible, two tools were created with intuitive graphical user interfaces (GUIs). The first tool allows payload designers to graphically design their payload by using simple drag and drop of payload components onto a design area within the program. Information about each picked component is pulled from a database of common space-qualified communication components sold by commerical companies. Once a design is completed, various reports can be generated, such as the Master Equipment List. The second tool is a link budget calculator designed specifically for ease of use. Other features of this tool include being able to access a database of NASA ground based apertures for near Earth and Deep Space communication, the Tracking and Data Relay Satellite System (TDRSS) base apertures, and information about the solar system relevant to link budget calculations. The link budget tool allows for over 50 different combinations of user inputs, eliminating the need for multiple spreadsheets and the user errors associated with using them. Both of the aforementioned tools increase the productivity of space communication systems designers, and have the colloquial latitude to allow non-communication experts to design preliminary communication payloads

Enhanced magnetic response of fluids using self-assembled petal-like iron oxide particles

Using self-assembled iron oxide (SAIO) particles with petal-like morphology, aqueous fluids containing magnetic particles were prepared and the effect of hierarchical particle surface on the viscoelasticity under magnetic was investigated. The fluids consisting of self-assembled iron oxide particles exhibit highly tunable viscoelasticity which is controlled by applying external magnetic field. A difference between SAIO particles and spherical particles is explained by the fact that surface features of the self-assembled particles increased the network strength between particles in the fluids. © 2010 American Institute of Physics

Detection of broken rotor bar faults and effects of loading in induction motors during rundown

© Copyright 2007 IEEEThe detection of broken rotor bar faults based on the common steady-state Fourier transform technique is known to be dependent on the loading condition and the quality of the supply. This paper attempts to minimise these issues by utilising the induced voltage in the stator windings after supply disconnection. When the supply is disconnected, the stator current rapidly drops to zero and the only source of the stator induced voltage an instant after the supply disconnection is due to currents in the rotor. The rotor currents are sensitive to broken rotor bar faults and directly affect the rundown induced voltage in the stator windings. The performance of two different broken rotor bar detection techniques, based on the Fourier transform and the wavelet transform, are investigated over a wide range of loading conditions