The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Ahmed M. Massoud - One of the best experts on this subject based on the ideXlab platform.
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An Improved Fault-Tolerant Five-Phase Induction Machine Using a Combined Star/Pentagon Single Layer Stator Winding Connection
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Ayman S. Abdel-khalik, Mohamed A. Elgenedy, Shehab Ahmed, Ahmed M. MassoudAbstract:One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower Derating Factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower Derating Factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.
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an improved fault tolerant five phase induction machine using a combined star pentagon single layer stator winding connection
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Ayman S Abdelkhalik, Mohamed A. Elgenedy, Shehab Ahmed, Ahmed M. MassoudAbstract:One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower Derating Factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower Derating Factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.
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effect of stator winding connection on performance of five phase induction machines
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Ayman S Abdelkhalik, Shehab Ahmed, Ahmed S Morsy, Ahmed M. MassoudAbstract:This paper studies the effect of stator winding configuration on the performance of five-phase induction machines under healthy as well as faulty conditions. The study compares two connections, namely, star and pentagon connections. The comparison is conducted using both simulation and experimental results. The steady-state model based on symmetrical components theory is introduced for both connections with one-line open due to a converter fault, and the corresponding machine characteristic curves are estimated. During faults, two alternatives for machine operation are possible, namely, open-loop control and optimal current control. While the first alternative corresponds to higher torque ripple and unbalanced winding currents, the second option necessitates unbalanced phase voltages and typically an increased dc-link voltage to source the required optimal currents. Consequently, an increase in the employed semiconductor device rating is required, which is a critical design Factor particularly in medium-voltage applications. A new V/f control technique is proposed to ensure disturbance-free operation with one-line open for both winding connections. Based on the unbalanced machine model and experimental verification, the Derating Factors that ensure safe machine operation for both winding connection alternatives are calculated. The comparison between the two connections shows the superiority of the pentagon connection under fault conditions in terms of efficiency, average torque, torque ripples, and Derating Factor.
Tarun Kumar Aseri - One of the best experts on this subject based on the ideXlab platform.
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CFD analysis based parametric study of Derating Factor for Earth Air Tunnel Heat Exchanger
Applied Energy, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics modeling. Effects of time duration of continuous operation, thermal conductivity of soil pipe diameter and flow velocity on thermal performance of EATHE under transient conditions have been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of EATHE. Study reveals that the effect of pipe diameter due to prolonged use of EATHE system on its thermal performance is least in case of soil with higher value of thermal conductivity. Results show that the increase in flow velocity leads to deterioration in thermal performance of EATHE system. Under steady state condition, drop of 18.8 °C in air temperature is obtained, whereas, under transient conditions cooling of air reduces from 18.7 °C to 16.6 °C for soil thermal conductivity of 0.52 W m−1 K−1, after 24 h of continuous operation.
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Transient analysis based determination of Derating Factor for earth air tunnel heat exchanger in summer
Energy and Buildings, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions in winter season has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics (CFD) modeling. Effect of time duration of continuous operation and thermal conductivity of soil on thermal performance of EATHE under transient conditions has been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. Under steady state condition, a rise of 19.6 °C is obtained in air passing through EATHE having 0.1 m diameter and 60 m length, at 5 m/s flow velocity, whereas, the transient analysis shows that for soil having thermal conductivity of 0.52 Wm −1 K −1 , the heating of air reduces from 19.4 °C to 17.2 °C, after 24 h of continuous operation. Heating effect after 24 h of operation for soil thermal conductivity of 2.0 Wm −1 K −1 and 4.0 Wm −1 K −1 , reduced from 19.6 °C to 19.2 °C and 19.6 °C to 19.5 °C, respectively. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of earth air heat exchangers.
Jyotirmay Mathur - One of the best experts on this subject based on the ideXlab platform.
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‘Derating Factor’ new concept for evaluating thermal performance of earth air tunnel heat exchanger: A transient CFD analysis
Applied Energy, 2013Co-Authors: Vikas Bansal, Rohit Misra, Ghanshyam Das Agarwal, Jyotirmay MathurAbstract:Abstract A new term ‘Derating Factor’ is devised for evaluating deterioration in thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions in predominantly hot and dry climate of Ajmer (India) using experimental and computational fluid dynamics modeling with FLUENT software. Maximum air temperature drop obtained using steady state approach for EATHE of pipe length 100 m, pipe diameter 0.2 m and at air velocity of 5 m s−1 is 18.4 °C, 18.7 °C and 18.4 °C for soil thermal conductivity of 0.52, 2.0 and 4.0 W m−1 K−1 respectively. However, the maximum air temperature drop obtained using transient approach during 24 h of operation vary between 18.3 °C and 14.0 °C, 18.3 °C and 17.2 °C and 18.6 °C and 18.0 °C for soil thermal conductivity of 0.52, 2.0 and 4.0 W m−1 K−1 respectively. The Derating Factor is found to be a function of thermal conductivity of soil, duration of continuous operation of EATHE and length of pipe. The analyzed cases have shown the range of Derating to be as minimal as 0.2% to as high as 68%, which if ignored while designing may lead to poor performance of earth air heat exchangers. Maximum value of Derating Factor is observed after continuous operation of EATHE for 24 h.
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CFD analysis based parametric study of Derating Factor for Earth Air Tunnel Heat Exchanger
Applied Energy, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics modeling. Effects of time duration of continuous operation, thermal conductivity of soil pipe diameter and flow velocity on thermal performance of EATHE under transient conditions have been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of EATHE. Study reveals that the effect of pipe diameter due to prolonged use of EATHE system on its thermal performance is least in case of soil with higher value of thermal conductivity. Results show that the increase in flow velocity leads to deterioration in thermal performance of EATHE system. Under steady state condition, drop of 18.8 °C in air temperature is obtained, whereas, under transient conditions cooling of air reduces from 18.7 °C to 16.6 °C for soil thermal conductivity of 0.52 W m−1 K−1, after 24 h of continuous operation.
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Transient analysis based determination of Derating Factor for earth air tunnel heat exchanger in summer
Energy and Buildings, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions in winter season has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics (CFD) modeling. Effect of time duration of continuous operation and thermal conductivity of soil on thermal performance of EATHE under transient conditions has been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. Under steady state condition, a rise of 19.6 °C is obtained in air passing through EATHE having 0.1 m diameter and 60 m length, at 5 m/s flow velocity, whereas, the transient analysis shows that for soil having thermal conductivity of 0.52 Wm −1 K −1 , the heating of air reduces from 19.4 °C to 17.2 °C, after 24 h of continuous operation. Heating effect after 24 h of operation for soil thermal conductivity of 2.0 Wm −1 K −1 and 4.0 Wm −1 K −1 , reduced from 19.6 °C to 19.2 °C and 19.6 °C to 19.5 °C, respectively. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of earth air heat exchangers.
Rohit Misra - One of the best experts on this subject based on the ideXlab platform.
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‘Derating Factor’ new concept for evaluating thermal performance of earth air tunnel heat exchanger: A transient CFD analysis
Applied Energy, 2013Co-Authors: Vikas Bansal, Rohit Misra, Ghanshyam Das Agarwal, Jyotirmay MathurAbstract:Abstract A new term ‘Derating Factor’ is devised for evaluating deterioration in thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions in predominantly hot and dry climate of Ajmer (India) using experimental and computational fluid dynamics modeling with FLUENT software. Maximum air temperature drop obtained using steady state approach for EATHE of pipe length 100 m, pipe diameter 0.2 m and at air velocity of 5 m s−1 is 18.4 °C, 18.7 °C and 18.4 °C for soil thermal conductivity of 0.52, 2.0 and 4.0 W m−1 K−1 respectively. However, the maximum air temperature drop obtained using transient approach during 24 h of operation vary between 18.3 °C and 14.0 °C, 18.3 °C and 17.2 °C and 18.6 °C and 18.0 °C for soil thermal conductivity of 0.52, 2.0 and 4.0 W m−1 K−1 respectively. The Derating Factor is found to be a function of thermal conductivity of soil, duration of continuous operation of EATHE and length of pipe. The analyzed cases have shown the range of Derating to be as minimal as 0.2% to as high as 68%, which if ignored while designing may lead to poor performance of earth air heat exchangers. Maximum value of Derating Factor is observed after continuous operation of EATHE for 24 h.
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CFD analysis based parametric study of Derating Factor for Earth Air Tunnel Heat Exchanger
Applied Energy, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics modeling. Effects of time duration of continuous operation, thermal conductivity of soil pipe diameter and flow velocity on thermal performance of EATHE under transient conditions have been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of EATHE. Study reveals that the effect of pipe diameter due to prolonged use of EATHE system on its thermal performance is least in case of soil with higher value of thermal conductivity. Results show that the increase in flow velocity leads to deterioration in thermal performance of EATHE system. Under steady state condition, drop of 18.8 °C in air temperature is obtained, whereas, under transient conditions cooling of air reduces from 18.7 °C to 16.6 °C for soil thermal conductivity of 0.52 W m−1 K−1, after 24 h of continuous operation.
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Transient analysis based determination of Derating Factor for earth air tunnel heat exchanger in summer
Energy and Buildings, 2013Co-Authors: Rohit Misra, Vikas Bansal, Jyotirmay Mathur, Ghanshyam Das Agrawal, Tarun Kumar AseriAbstract:Abstract Thermal performance of Earth Air Tunnel Heat Exchanger (EATHE) under transient operating conditions in winter season has been evaluated for predominantly hot and dry climate of Ajmer (India) using experimental and Computational Fluid Dynamics (CFD) modeling. Effect of time duration of continuous operation and thermal conductivity of soil on thermal performance of EATHE under transient conditions has been analyzed. Results show that the transient thermal performance of EATHE is significantly dependent on thermal conductivity of the soil and duration of its continuous operation. Under steady state condition, a rise of 19.6 °C is obtained in air passing through EATHE having 0.1 m diameter and 60 m length, at 5 m/s flow velocity, whereas, the transient analysis shows that for soil having thermal conductivity of 0.52 Wm −1 K −1 , the heating of air reduces from 19.4 °C to 17.2 °C, after 24 h of continuous operation. Heating effect after 24 h of operation for soil thermal conductivity of 2.0 Wm −1 K −1 and 4.0 Wm −1 K −1 , reduced from 19.6 °C to 19.2 °C and 19.6 °C to 19.5 °C, respectively. The analyzed cases have shown the range of Derating to be as minimal as 0% to as high as 64%, which if ignored while designing may lead to poor performance of earth air heat exchangers.
Shehab Ahmed - One of the best experts on this subject based on the ideXlab platform.
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An Improved Fault-Tolerant Five-Phase Induction Machine Using a Combined Star/Pentagon Single Layer Stator Winding Connection
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Ayman S. Abdel-khalik, Mohamed A. Elgenedy, Shehab Ahmed, Ahmed M. MassoudAbstract:One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower Derating Factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower Derating Factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.
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an improved fault tolerant five phase induction machine using a combined star pentagon single layer stator winding connection
IEEE Transactions on Industrial Electronics, 2016Co-Authors: Ayman S Abdelkhalik, Mohamed A. Elgenedy, Shehab Ahmed, Ahmed M. MassoudAbstract:One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower Derating Factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower Derating Factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.
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effect of stator winding connection on performance of five phase induction machines
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Ayman S Abdelkhalik, Shehab Ahmed, Ahmed S Morsy, Ahmed M. MassoudAbstract:This paper studies the effect of stator winding configuration on the performance of five-phase induction machines under healthy as well as faulty conditions. The study compares two connections, namely, star and pentagon connections. The comparison is conducted using both simulation and experimental results. The steady-state model based on symmetrical components theory is introduced for both connections with one-line open due to a converter fault, and the corresponding machine characteristic curves are estimated. During faults, two alternatives for machine operation are possible, namely, open-loop control and optimal current control. While the first alternative corresponds to higher torque ripple and unbalanced winding currents, the second option necessitates unbalanced phase voltages and typically an increased dc-link voltage to source the required optimal currents. Consequently, an increase in the employed semiconductor device rating is required, which is a critical design Factor particularly in medium-voltage applications. A new V/f control technique is proposed to ensure disturbance-free operation with one-line open for both winding connections. Based on the unbalanced machine model and experimental verification, the Derating Factors that ensure safe machine operation for both winding connection alternatives are calculated. The comparison between the two connections shows the superiority of the pentagon connection under fault conditions in terms of efficiency, average torque, torque ripples, and Derating Factor.