Diabetes mellitus (DM) has been suggested to be the most common metabolic disorder associated wit... more Diabetes mellitus (DM) has been suggested to be the most common metabolic disorder associated with several macrovascular and microvascular complications. Hypomagnesemia has been reported to occur at an increased frequency among patients with type-2 DM. Those who have poor glycemic control and longtime DM are more likely to decrease the blood magnesium (Mg) level. Mg deficit may also coexist with deficiencies of other dietary elements, such as vitamins, calcium (Ca++) and potassium (K+). Despite numerous reports linking hypomagnesemia to chronic diabetic complications, attention to this issue is poor among clinicians. This article reviews the literature on physiology & biochemistry of Mg++ diagnosis and incidence, features, causes, complications and management of hypomagnesemia in patients with type-2 DM. EMCJ. January 2022; 7(1): 26-31
This paper presents a comparative study of the transient stability between a five-phase and three... more This paper presents a comparative study of the transient stability between a five-phase and three-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM). In automotive industries, the reliability of the motor drive system has become a critical concern to ensure optimal safety. Five-phase PMa-SynRMs are suggested in the critical applications for their fault-tolerant capability. However, their transient performance over the conventional three-phase system has not been discussed in detail. Additionally, PMa-SynRMs show higher cross-coupling effects which cause strong dynamic outcomes. This paper presents the stability comparison between an optimally designed three-phase and five-phase PMa-SynRM. Detail theoretical analysis is carried out through the MATLAB and finite element analysis (FEA).
A performance comparison between a rareearth and a rare-earth-free five-phase PMa-SynRMs operatin... more A performance comparison between a rareearth and a rare-earth-free five-phase PMa-SynRMs operating at maximum torque per ampere (MTPA) control is present in this paper under different open phase faults. The five-phase machines show inherent higher fault tolerance advantageous over the conventional three-phase machine under different number of open-phase conditions. Ferrite (Fe) magnets are cost effective replacement of the rare-earth material e.g. neodymium (Nd) magnets. Both magnets in PMa-SynRMs show degraded electromagnetic torque characteristics under different open phase faults. Traditional MTPA control method is not able to improve performance under faulty conditions. Advanced fault-tolerant MTPA control method is required to achieve satisfactory performance both under healthy and faulty conditions. In this paper, the fault tolerant control method is modified with MTPA technique to achieve higher performance. The proposed technique is applied on both machines under open phase faults to compare their performances. Detail theoretical analysis is carried out through MATLAB and finite element analysis (FEA). Experimental test results are provided for the Nd-based PMa-SynRM.
This paper proposes the design of a five-phase bearingless permanent magnet assisted synchronous ... more This paper proposes the design of a five-phase bearingless permanent magnet assisted synchronous machine (PMaSynRM) for high speed applications. The bearingless machines are suitable for various industrial and medical applications as they offer wear-free operation, longer lifetime, and higher efficiency by eliminating mechanical bearings. However, the levitation of the rotor is critical aspect in these machines which needs very smooth and sustainable force to hold the rotor and shaft at proper position. In that regard, multiphase PMaSynRM, which offers very low torque ripple and high fault-tolerance, is a suitable candidate for bearingless machine applications. Therefore, this study proposes a five-phase bearingless PMaSynRM that generates desired torque using main five-phase winding and generates the rotor-levitating force using an additional winding. The design procedure of the main motor and the suspension winding has been described in details. A thorough FEA analysis has been provided to show the performance characteristics under various operating conditions. The simulation results show that the motor generate required levitation force at cost of very low suspension winding current. The motor performance with and without the suspension has been compared to ensure desired output of the motor.
The objective of this study was to isolate and characterize Lactic Acid Bacteria (LAB) from raw g... more The objective of this study was to isolate and characterize Lactic Acid Bacteria (LAB) from raw goat milk, and to evaluate their probiotic attributes, technological properties and safety profiles. A total of 50 LAB strains were isolated and identified from 18 goat milk samples based on their morphological, physiological, biochemical, and genotypic characteristics. We found the existence of 6 genera where Lactobacillus was found as dominant (50 %). The in-vitro experiment showed that more than 80 % of the representative LAB strains inhibited the growth of tested pathogenic microorganisms. Out of 11 tested LAB strains, most of them exhibited moderate to high survivability (80-100 %) under intestinal juice, pancreatic juice and bile salt, and which was 70-80 % at low pH conditions. All tested LAB strains produced diacetyl, and 73 % of the tested strains showed proteolytic activity whereas only 27 % strains exhibited weak lipolysis. In case of antibiotic susceptibility, most of the LAB strains exhibited resistance against the tested antibiotics. All LAB strains produced exopolysaccharide to a variable extent ranging from 20 to 93 mg/L where the Lactobacillus delbrueckii subsp. bulgaricus being the greatest producer. The in-vitro experiments regarding safety profile showed that all the isolated LAB strains were found as non-virulence. Furthermore, our lab-scale fermentation study demonstrated that most isolated LAB strains possess the starter culture properties for producing firm milk curd. In conclusion, this study revealed that the isolated LAB strains from raw goat milk retain the potential to be used in fermented foods because of their safety aspects, probiotic attributes, and technological characteristics.
This paper presents the performance comparisons between rare-earth and rare-earth free external r... more This paper presents the performance comparisons between rare-earth and rare-earth free external rotor permanent magnet assisted synchronous reluctance motors (PMa-SynRMs) under static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME) conditions. Recently, external rotor motors are proposed as high power density motors for traction applications in electric vehicles and more electric aircraft. However, these in-wheel external rotor motors are usually under continuous stress of rotational forces due to the tire-road friction which can result in eccentricity faults due to stator and rotor misalignment. Therefore, it is critical to assess the external rotor motors performance under eccentricity faults in traction motors. In this study, various failure modes due to eccentricity faults such as SE, DE, and ME conditions are analyzed on optimal 3.8kW rare-earth based and 3.7kW rare-earth free external rotor PMa-SynRMs. Effects of these eccentricity conditions are translated to performance loss in terms of increased torque ripple and unbalanced magnetic pull (UMP) in the electric motor designs. Also, 3rd harmonics of back-electromotive force (back-EMF) have been analyzed for both motors in all eccentricity conditions to compare their performance in fault detection. Experimental setup is developed to test the motors under load conditions and finite element simulation results are presented to validate the proposed theory.
This paper compares the performance of five-phase external rotor permanent magnet assisted synchr... more This paper compares the performance of five-phase external rotor permanent magnet assisted synchronous reluctance motor (PMaSynRMs) for two different winding configurations. In vehicle applications, five-phase winding improves power density, fault tolerant capability and reduces torque pulsation compared to a conventional three-phase winding whereas the adoption of external rotor architecture increases the power density. However, the degree of freedom reduces in selecting winding configuration for multiphase motors which is very critical for performance of PMaSynRM. Therefore, for the design external rotor PMaSynRM, the winding topology like slot/pole combination and coil-distribution should be carefully selected to obtain higher power density with higher efficiency and lower cost. This paper compares the electromagnetic performance of two motors having two different winding topologies, one has fractional-slot concentrated winding (FSCW) with 15slot/12pole and the other one has fractional-slot distributed winding with 25slot/12pole. The analytical modeling and optimization procedure to obtain these motors have been discussed briefly followed by thorough finite element analysis to compare the performance of the motors. Finally, the experimental results have been presented to verify the induced voltage of one motor at no load condition.
This paper presents the design considerations of a five-phase outer rotor interior permanent magn... more This paper presents the design considerations of a five-phase outer rotor interior permanent magnet motor (IPM) for an electric bicycle (e-bicycle). Conventional e-bicycles employ three phase outer rotor surface permanent magnet motors which are less reliable compared to the five-phase IPM motors. Moreover, the traditional electric motors use rare-earth permanent magnet materials such as neodymium which are expensive. Ferrite based magnets can be a better substitute to rare earth materials to make the motor more affordable. In this study, the design of a highly reliable and economical five-phase ferrite based IPM motor to be accommodated in a hub motor drive (HMD) for an e-bicycle is presented. The proposed motor design is optimized using a lumped parameter model (LPM) based optimizer. Detailed analysis on the design parameters and constraints considered for optimization is discussed. Thorough finite element simulations in terms of torque developed, cogging torque, back-EMF, and mechanical stress have been conducted to verify the effectiveness of the proposed motor design.
ABSTRACT This paper proposes an efficient and reliable five-phase ferrite magnet assisted synchro... more ABSTRACT This paper proposes an efficient and reliable five-phase ferrite magnet assisted synchronous reluctance motor (Fa-SynRM) which exhibits comparable performance to a five-phase rare-earth permanent magnet based PMa-SynRM. Five-phase PMa-SynRM offers higher reliability and lower torque ripple compared to conventional three phase PMa-SynRMs, and low-cost ferrite magnet potentially decrease the manufacturing cost. However, lower strength of ferrite magnets require more magnet composition and increase stress towards the edges of flux barriers. Demagnetization of ferrite magnets is another factor to be considered in designing the Fa-SynRM. Initially, to develop an optimal and sustainable design, a lumped parameter model (LPM) based optimizer and a finite element model (FEA) has been used to extract an optimal model. The designs are further optimized to reduce the cost and develop more robust models to stress and demagnetization. Finally, the performance and cost of the developed models have been compared to those of benchmark model and initial LPM model.
This paper presents the process of determining demagnetization-free operating region of multi-pha... more This paper presents the process of determining demagnetization-free operating region of multi-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) under fault tolerant operating condition using finite element analysis (FEA) tool. The five-phase PMa-SynRM has been considered as a suitable candidate for many critical service applications such as aircraft, electric vehicles, and electric ships due to low cost and high fault-tolerance capability. These machines can generate required torque under single or two-phase fault using only the unaffected phases. However, under the fault condition, the air-gap magnetomotive force (MMF) will be distorted and cause additional harmonics loss and torque ripple. Although the adoption of fault tolerant control (FTC) scheme can improve the performance, there will be large rise and fall in the air-gap MMF which can be threatening to the permanent magnet (PM) for irreversible demagnetization. Therefore, multiphase PMa-SynRM should be carefully operated under FTC to avoid the irreversible demagnetization of its PMs. This study determines the demagnetization-free operating region of a 3 kW five-phase rare-earth (NdFeB35) PM based PMa-SynRM under single and two-phase open fault conditions. Finite element analysis (FEA) has been performed for different thermal levels of the PMs to evaluate the operating range of the motor without demagnetization.
This paper provides a performance comparison between three-phase and five-phase ferrite-based per... more This paper provides a performance comparison between three-phase and five-phase ferrite-based permanent magnet assisted synchronous reluctance motor (PMa-SynRM). Recently, research on PMa-SynRM has got significant attention, especially in vehicular applications. They can meet the performance requirements of electric vehicles with reduced or no use of rare-earth-based permanent magnets (PMs). However, these motors face the challenges of lower torque density, irreversible demagnetization tendency, and intolerance to the augmented stress due to the relatively higher amount of PM. These challenges can be mitigated by employing five-phase winding which can develop higher power density with lower torque pulsation compared to the conventional three-phase motor. This paper compares the electromagnetic performance of a three-phase and five-phase Ferrite magnet based PMa-SynRM. A thorough finite element analysis (FEA) has been presented to validate the superior demagnetization preventing capability, and stress tolerance capability of the five-phase PMa-SynRM over the three-phase PMa-SynRM. Experimental results of the induced voltage for fabricated three-phase and five-phase PMa-SynRMs will be provided to validate the FEA results.
Diabetes mellitus (DM) has been suggested to be the most common metabolic disorder associated wit... more Diabetes mellitus (DM) has been suggested to be the most common metabolic disorder associated with several macrovascular and microvascular complications. Hypomagnesemia has been reported to occur at an increased frequency among patients with type-2 DM. Those who have poor glycemic control and longtime DM are more likely to decrease the blood magnesium (Mg) level. Mg deficit may also coexist with deficiencies of other dietary elements, such as vitamins, calcium (Ca++) and potassium (K+). Despite numerous reports linking hypomagnesemia to chronic diabetic complications, attention to this issue is poor among clinicians. This article reviews the literature on physiology & biochemistry of Mg++ diagnosis and incidence, features, causes, complications and management of hypomagnesemia in patients with type-2 DM. EMCJ. January 2022; 7(1): 26-31
This paper presents a comparative study of the transient stability between a five-phase and three... more This paper presents a comparative study of the transient stability between a five-phase and three-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM). In automotive industries, the reliability of the motor drive system has become a critical concern to ensure optimal safety. Five-phase PMa-SynRMs are suggested in the critical applications for their fault-tolerant capability. However, their transient performance over the conventional three-phase system has not been discussed in detail. Additionally, PMa-SynRMs show higher cross-coupling effects which cause strong dynamic outcomes. This paper presents the stability comparison between an optimally designed three-phase and five-phase PMa-SynRM. Detail theoretical analysis is carried out through the MATLAB and finite element analysis (FEA).
A performance comparison between a rareearth and a rare-earth-free five-phase PMa-SynRMs operatin... more A performance comparison between a rareearth and a rare-earth-free five-phase PMa-SynRMs operating at maximum torque per ampere (MTPA) control is present in this paper under different open phase faults. The five-phase machines show inherent higher fault tolerance advantageous over the conventional three-phase machine under different number of open-phase conditions. Ferrite (Fe) magnets are cost effective replacement of the rare-earth material e.g. neodymium (Nd) magnets. Both magnets in PMa-SynRMs show degraded electromagnetic torque characteristics under different open phase faults. Traditional MTPA control method is not able to improve performance under faulty conditions. Advanced fault-tolerant MTPA control method is required to achieve satisfactory performance both under healthy and faulty conditions. In this paper, the fault tolerant control method is modified with MTPA technique to achieve higher performance. The proposed technique is applied on both machines under open phase faults to compare their performances. Detail theoretical analysis is carried out through MATLAB and finite element analysis (FEA). Experimental test results are provided for the Nd-based PMa-SynRM.
This paper proposes the design of a five-phase bearingless permanent magnet assisted synchronous ... more This paper proposes the design of a five-phase bearingless permanent magnet assisted synchronous machine (PMaSynRM) for high speed applications. The bearingless machines are suitable for various industrial and medical applications as they offer wear-free operation, longer lifetime, and higher efficiency by eliminating mechanical bearings. However, the levitation of the rotor is critical aspect in these machines which needs very smooth and sustainable force to hold the rotor and shaft at proper position. In that regard, multiphase PMaSynRM, which offers very low torque ripple and high fault-tolerance, is a suitable candidate for bearingless machine applications. Therefore, this study proposes a five-phase bearingless PMaSynRM that generates desired torque using main five-phase winding and generates the rotor-levitating force using an additional winding. The design procedure of the main motor and the suspension winding has been described in details. A thorough FEA analysis has been provided to show the performance characteristics under various operating conditions. The simulation results show that the motor generate required levitation force at cost of very low suspension winding current. The motor performance with and without the suspension has been compared to ensure desired output of the motor.
The objective of this study was to isolate and characterize Lactic Acid Bacteria (LAB) from raw g... more The objective of this study was to isolate and characterize Lactic Acid Bacteria (LAB) from raw goat milk, and to evaluate their probiotic attributes, technological properties and safety profiles. A total of 50 LAB strains were isolated and identified from 18 goat milk samples based on their morphological, physiological, biochemical, and genotypic characteristics. We found the existence of 6 genera where Lactobacillus was found as dominant (50 %). The in-vitro experiment showed that more than 80 % of the representative LAB strains inhibited the growth of tested pathogenic microorganisms. Out of 11 tested LAB strains, most of them exhibited moderate to high survivability (80-100 %) under intestinal juice, pancreatic juice and bile salt, and which was 70-80 % at low pH conditions. All tested LAB strains produced diacetyl, and 73 % of the tested strains showed proteolytic activity whereas only 27 % strains exhibited weak lipolysis. In case of antibiotic susceptibility, most of the LAB strains exhibited resistance against the tested antibiotics. All LAB strains produced exopolysaccharide to a variable extent ranging from 20 to 93 mg/L where the Lactobacillus delbrueckii subsp. bulgaricus being the greatest producer. The in-vitro experiments regarding safety profile showed that all the isolated LAB strains were found as non-virulence. Furthermore, our lab-scale fermentation study demonstrated that most isolated LAB strains possess the starter culture properties for producing firm milk curd. In conclusion, this study revealed that the isolated LAB strains from raw goat milk retain the potential to be used in fermented foods because of their safety aspects, probiotic attributes, and technological characteristics.
This paper presents the performance comparisons between rare-earth and rare-earth free external r... more This paper presents the performance comparisons between rare-earth and rare-earth free external rotor permanent magnet assisted synchronous reluctance motors (PMa-SynRMs) under static eccentricity (SE), dynamic eccentricity (DE), and mixed eccentricity (ME) conditions. Recently, external rotor motors are proposed as high power density motors for traction applications in electric vehicles and more electric aircraft. However, these in-wheel external rotor motors are usually under continuous stress of rotational forces due to the tire-road friction which can result in eccentricity faults due to stator and rotor misalignment. Therefore, it is critical to assess the external rotor motors performance under eccentricity faults in traction motors. In this study, various failure modes due to eccentricity faults such as SE, DE, and ME conditions are analyzed on optimal 3.8kW rare-earth based and 3.7kW rare-earth free external rotor PMa-SynRMs. Effects of these eccentricity conditions are translated to performance loss in terms of increased torque ripple and unbalanced magnetic pull (UMP) in the electric motor designs. Also, 3rd harmonics of back-electromotive force (back-EMF) have been analyzed for both motors in all eccentricity conditions to compare their performance in fault detection. Experimental setup is developed to test the motors under load conditions and finite element simulation results are presented to validate the proposed theory.
This paper compares the performance of five-phase external rotor permanent magnet assisted synchr... more This paper compares the performance of five-phase external rotor permanent magnet assisted synchronous reluctance motor (PMaSynRMs) for two different winding configurations. In vehicle applications, five-phase winding improves power density, fault tolerant capability and reduces torque pulsation compared to a conventional three-phase winding whereas the adoption of external rotor architecture increases the power density. However, the degree of freedom reduces in selecting winding configuration for multiphase motors which is very critical for performance of PMaSynRM. Therefore, for the design external rotor PMaSynRM, the winding topology like slot/pole combination and coil-distribution should be carefully selected to obtain higher power density with higher efficiency and lower cost. This paper compares the electromagnetic performance of two motors having two different winding topologies, one has fractional-slot concentrated winding (FSCW) with 15slot/12pole and the other one has fractional-slot distributed winding with 25slot/12pole. The analytical modeling and optimization procedure to obtain these motors have been discussed briefly followed by thorough finite element analysis to compare the performance of the motors. Finally, the experimental results have been presented to verify the induced voltage of one motor at no load condition.
This paper presents the design considerations of a five-phase outer rotor interior permanent magn... more This paper presents the design considerations of a five-phase outer rotor interior permanent magnet motor (IPM) for an electric bicycle (e-bicycle). Conventional e-bicycles employ three phase outer rotor surface permanent magnet motors which are less reliable compared to the five-phase IPM motors. Moreover, the traditional electric motors use rare-earth permanent magnet materials such as neodymium which are expensive. Ferrite based magnets can be a better substitute to rare earth materials to make the motor more affordable. In this study, the design of a highly reliable and economical five-phase ferrite based IPM motor to be accommodated in a hub motor drive (HMD) for an e-bicycle is presented. The proposed motor design is optimized using a lumped parameter model (LPM) based optimizer. Detailed analysis on the design parameters and constraints considered for optimization is discussed. Thorough finite element simulations in terms of torque developed, cogging torque, back-EMF, and mechanical stress have been conducted to verify the effectiveness of the proposed motor design.
ABSTRACT This paper proposes an efficient and reliable five-phase ferrite magnet assisted synchro... more ABSTRACT This paper proposes an efficient and reliable five-phase ferrite magnet assisted synchronous reluctance motor (Fa-SynRM) which exhibits comparable performance to a five-phase rare-earth permanent magnet based PMa-SynRM. Five-phase PMa-SynRM offers higher reliability and lower torque ripple compared to conventional three phase PMa-SynRMs, and low-cost ferrite magnet potentially decrease the manufacturing cost. However, lower strength of ferrite magnets require more magnet composition and increase stress towards the edges of flux barriers. Demagnetization of ferrite magnets is another factor to be considered in designing the Fa-SynRM. Initially, to develop an optimal and sustainable design, a lumped parameter model (LPM) based optimizer and a finite element model (FEA) has been used to extract an optimal model. The designs are further optimized to reduce the cost and develop more robust models to stress and demagnetization. Finally, the performance and cost of the developed models have been compared to those of benchmark model and initial LPM model.
This paper presents the process of determining demagnetization-free operating region of multi-pha... more This paper presents the process of determining demagnetization-free operating region of multi-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) under fault tolerant operating condition using finite element analysis (FEA) tool. The five-phase PMa-SynRM has been considered as a suitable candidate for many critical service applications such as aircraft, electric vehicles, and electric ships due to low cost and high fault-tolerance capability. These machines can generate required torque under single or two-phase fault using only the unaffected phases. However, under the fault condition, the air-gap magnetomotive force (MMF) will be distorted and cause additional harmonics loss and torque ripple. Although the adoption of fault tolerant control (FTC) scheme can improve the performance, there will be large rise and fall in the air-gap MMF which can be threatening to the permanent magnet (PM) for irreversible demagnetization. Therefore, multiphase PMa-SynRM should be carefully operated under FTC to avoid the irreversible demagnetization of its PMs. This study determines the demagnetization-free operating region of a 3 kW five-phase rare-earth (NdFeB35) PM based PMa-SynRM under single and two-phase open fault conditions. Finite element analysis (FEA) has been performed for different thermal levels of the PMs to evaluate the operating range of the motor without demagnetization.
This paper provides a performance comparison between three-phase and five-phase ferrite-based per... more This paper provides a performance comparison between three-phase and five-phase ferrite-based permanent magnet assisted synchronous reluctance motor (PMa-SynRM). Recently, research on PMa-SynRM has got significant attention, especially in vehicular applications. They can meet the performance requirements of electric vehicles with reduced or no use of rare-earth-based permanent magnets (PMs). However, these motors face the challenges of lower torque density, irreversible demagnetization tendency, and intolerance to the augmented stress due to the relatively higher amount of PM. These challenges can be mitigated by employing five-phase winding which can develop higher power density with lower torque pulsation compared to the conventional three-phase motor. This paper compares the electromagnetic performance of a three-phase and five-phase Ferrite magnet based PMa-SynRM. A thorough finite element analysis (FEA) has been presented to validate the superior demagnetization preventing capability, and stress tolerance capability of the five-phase PMa-SynRM over the three-phase PMa-SynRM. Experimental results of the induced voltage for fabricated three-phase and five-phase PMa-SynRMs will be provided to validate the FEA results.
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Papers by Zakirul Islam