PFC Bridge Converter for Voltage-controlled Adjustable-speed PMBLDCM Drive

Sanjeev Singh,Bhim Singh 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.2

In this paper, a buck DC-DC bridge converter is used as a power factor correction (PFC) converter for feeding a voltage source inverter (VSI) based permanent magnet brushless DC motor (PMBLDCM) drive. The front end of the PFC converter is a diode bridge rectifier (DBR) fed from single phase AC mains. The PMBLDCM is used to drive the compressor of an air conditioner through a three-phase voltage source inverter (VSI) fed from a variable voltage DC link. The speed of the air conditioner is controlled to conserve energy using a new concept of voltage control at a DC link proportional to the desired speed of the PMBLDC motor. Therefore, VSI operates only as an electronic commutator of the PMBLDCM. The current of the PMBLDCM is controlled by setting the reference voltage at the DC link as a ramp. The proposed PMBLDCM drive with voltage control-based PFC converter was designed and modeled. The performance is simulated in Matlab-Simulink environment for an air conditioner compressor load driven through a 3.75 ㎾, 1500 rpm PMBLDC motor. To validate the effectiveness of the proposed speed control scheme, the evaluation results demonstrate improved efficiency of the complete drive with the PFC feature in a wide range of speed and input AC voltage.

PFC Bridge Converter for Voltage-controlled Adjustable-speed PMBLDCM Drive

Singh, Sanjeev,Singh, Bhim The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.2

In this paper, a buck DC-DC bridge converter is used as a power factor correction (PFC) converter for feeding a voltage source inverter (VSI) based permanent magnet brushless DC motor (PMBLDCM) drive. The front end of the PFC converter is a diode bridge rectifier (DBR) fed from single phase AC mains. The PMBLDCM is used to drive the compressor of an air conditioner through a three-phase voltage source inverter (VSI) fed from a variable voltage DC link. The speed of the air conditioner is controlled to conserve energy using a new concept of voltage control at a DC link proportional to the desired speed of the PMBLDC motor. Therefore, VSI operates only as an electronic commutator of the PMBLDCM. The current of the PMBLDCM is controlled by setting the reference voltage at the DC link as a ramp. The proposed PMBLDCM drive with voltage control-based PFC converter was designed and modeled. The performance is simulated in Matlab-Simulink environment for an air conditioner compressor load driven through a 3.75 kW, 1500 rpm PMBLDC motor. To validate the effectiveness of the proposed speed control scheme, the evaluation results demonstrate improved efficiency of the complete drive with the PFC feature in a wide range of speed and input AC voltage.

State of the Art on Permanent Magnet Brushless DC Motor Drives

Singh, Bhim,Singh, Sanjeev The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.1

Permanent magnet brushless DC (PMBLDC) motors are the latest choice of researchers due to their high efficiency, silent operation, compact size, high reliability and low maintenance requirements. These motors are preferred for numerous applications; however, most of them require sensorless control of these motors. The operation of PMBLDC motors requires rotor-position sensing for controlling the winding currents. The sensorless control would need estimation of rotor position from the voltage and current signals, which are easily sensed. This paper presents state of the art PMBLDC motor drives with an emphasis on sensorless control of these motors.

A hybrid Taguchi-artificial neural network approach to predict surface roughness during electric discharge machining of titanium alloys

Sanjeev Kumar,Ajay Batish,Rupinder Singh,T. P. Singh 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

In the present study, electric discharge machining process was used for machining of titanium alloys. Eight process parameters werevaried during the process. Experimental results showed that current and pulse-on-time significantly affected the performance characteristics. Artificial neural network coupled with Taguchi approach was applied for optimization and prediction of surface roughness. Theexperimental results and the predicted results showed good agreement. SEM was used to investigate the surface integrity. Analysis formigration of different chemical elements and formation of compounds on the surface was performed using EDS and XRD pattern. Theresults showed that high discharge energy caused surface defects such as cracks, craters, thick recast layer, micro pores, pin holes, residualstresses and debris. Also, migration of chemical elements both from electrode and dielectric media were observed during EDS analysis. Presence of carbon was seen on the machined surface. XRD results showed formation of titanium carbide compound which precipitatedon the machined surface.

Experimental Heat Transfer Coefficient and Pressure Drop during Condensation of R-134a and R-410A in Horizontal Micro-fin Tubes

Sanjeev Singh,Rajeev Kukreja 대한설비공학회 2018 International Journal Of Air-Conditioning and Refr Vol.26 No.3

Condensation heat transfer coefficients and pressure drops of HFC refrigerants R-134a and R-410A have been investigated experimentally in smooth and micro-fin tubes (helix angles 18° and 15°) of outer diameter 9.52mm at mass °uxes from 200 to 600 kg/m2 . s, vapor qualities between 0.1 and 0.9 and at saturation temperatures of 35°C and 40°C. Results showed that the heat transfer coefficients of R-134a and R-410A inside micro-fin tubes were 1.21–1.82 and 1.15–1.47 times higher and frictional pressure drops were 2.11–2.56 and 1.62–2.12 times higher than those of smooth tubes. These experimental results are compared with the existing heat transfer and frictional pressure drop correlations proposed by different researchers. The comparison showed fairly good agreement with these existing correlations within ±30%. A new correlation has also been proposed for predicting heat transfer coefficient in micro-fin tubes. The oil concentrations measured for refrigerants R-134a and R-410A varied in the range of 1.3–1.5%, respectively.

Temporary Endoscopic Stimulation in Gastroparesis-like Syndrome

( Sanjeev Singh ),( Jeff Mccrary ),( Archana Kedar ),( Stephen Weeks ),( Brian Beauerle ),( Andrew Weeks ),( Omer Endashaw ),( Chris Lahr ),( Warren Starkebaum ),( Thomas Abell ) 대한소화기기능성질환·운동학회 2015 Journal of Neurogastroenterology and Motility (JNM Vol.21 No.4

Background/Aims Gastroparesis-like syndrome (GLS) is defined as gastroparesis-like symptoms with normal gastric scintigraphy. While the efficacy of gastric electrical stimulation (GES) in gastroparesis is well known, the utility of GES in GLS is largely unknown. Our aim was to clarify the role of GES in GLS. We implanted consecutive patients with symptoms of gastroparesis with temporary gastric electrical stimulation and observed changes in gastric scintigraphy and total symptom score. Methods Five hundred and fifty-one patients suffering from symptoms of gastroparesis (nausea, vomiting, bloating/distension, anorexia/ early satiety, and abdominal pain) with negative endoscopy underwent gastric scintigraphy with analysis of 1) solid radionuclide gastric emptying at 1, 2, and 4 hours (% remaining); 2) area under the gastric emptying curve (AUC) at 1, 2, and 4hours; and 3) total gastric emptying test (GET) (the sum of 1, 2, and 4 hour values). Patients were stratified into: delayed gastric emptying, normal gastric emptying, and rapid gastric emptying (Appendix). Of the 551 patients in the larger cohort, 379 had implantation of temporary gastric electrical stimulation (tGES). Gastrointestinal symptoms and gastric emptying were com - pared pre and post tGES implantation. Results After tGES, 2 hour gastric retention decreased (P < 0.01) for the delayed patients, and increased (P < 0.001) for normal and rapid patients. These changes were accompanied by improvements (P < 0.001) in vomiting, nausea, and total symptom scores in all 3 subgroups. Conclusions Gastric electrical stimulation may be an effective therapy for treating the symptoms of gastroparesis with normal gastric emptying.Further exploration of endoscopic electrical stimulation as a treatment for gastroparesis-like symptoms with non-delayed gastric emptying is needed. (J Neurogastroenterol Motil 2015;21:520-527)

An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes

Sanjeev Singh,Rajeev Kukreja 대한설비공학회 2019 International Journal Of Air-Conditioning and Refr Vol.27 No.1

Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.

Histopathological changes in gall bladder mucosa in relation to the number, and size of gallstones, and analysis of the findings in the context of age distribution of the patients: A perspective

Sanjeev Sharma,Bhupinder Singh Walia,Mandeep Randhawa,Arjun Sharma,Pankaj Dugg,Jiteshwar Singh Pannu 한국간담췌외과학회 2023 Annals of hepato-biliary-pancreatic surgery Vol.27 No.3

Backgrounds/Aims: To study histopathological changes in gall bladder mucosa in cholelithiasis patients, and analyse their relation to the number and size of gallstones. These findings were evaluated in the context of age distribution of the study population. Methods: One hundred cases of cholecystectomy were part of the study, which was conducted in collaboration with the pathology department. The time period of the study was January 2020 to June 2021. Results: Maximum cases had multiple stones (69.0%), while one third cases (31.0%) had solitary stones. While initial univariate analysis showed age (odds ratio [OR], 6.882; p = 0.043), gallstone number (OR, 9.1; p = 0.050), gallstone size (OR, 17.111; p = 0.013), and duration of symptom (OR, 34.125; p = 0.001) to be significant risk factors associated with gallbladder carcinoma, multivariate analysis found none of these variables to be significant. However, conditional multivariate analysis for the duration of symptom (p = 0.008; OR, 21.118) yielded significant p- value. With histopathological diagnoses, 5% of cases had gallbladder cancer. Conclusions: This study shed light on the rising incidence of cholelithiasis in the young population and the high rate of gallbladder carcinoma in Punjab, India. Although gall stone characteristics (size, number) and patient age appeared to be significant risk factors when their individual relation with gallbladder carcinoma was studied, multivariate analysis, could not prove that. Conditional multivariate analysis showed the duration of symptom to be the only significant risk factor associated with gallbladder carcinoma. Further research with larger sample size is needed to study the rising incidence of gallbladder carcinoma, and the risk factors associated with it.

Impacts of Transparency and Disclosures on Firm Valuation of the Healthcare Sector in India

Saumya SINGH(Saumya SINGH ),Pracheta TEJASMAYEE(Pracheta TEJASMAYEE ),Venkata Mrudula BHIMAVARAPU(Venkata Mrudula BHIMAVARAPU ),Arpita SHARMA(Arpita SHARMA ),Rameesha KALRA(Rameesha KALRA ),Sanjeev KA 한국유통과학회 2023 The Journal of Asian Finance, Economics and Busine Vol.10 No.2

This study’s principal goal is to find the interrelation between transparency & disclosure (TD) and the healthcare sector’s firm valuation (FV). The paper uses the market-to-book (MTB) ratio and market capitalization as proxies, where sales measure act as a control variable. Dynamic panel data regression (PD) is the method applied for analyzing data. Data pertains to 10 healthcare companies gathered over five years (2016-2020). Results imply that TD has a negative and significant influence on the FV, where market capitalization acts as a proxy for valuation. This association indicates that a greater degree of TD diminishes FV. TD is also reported to have a negative and insignificant association with MTB. Therefore, TD does not influence FV. The findings of this paper have significant practical implications. Results can help policymakers determine mandatory disclosure levels that are not detrimental to the healthcare sector. Managers and analysts must also analyze the dimensions of disclosure that can negatively impact the firm’s valuation and make decisions regarding TD accordingly. This is the first study to assess the influence of TD on the FV of the Indian healthcare sector, which makes it unique. This study is limited to the healthcare sector, which is its shortcoming.

State-of-Art on Permanent Magnet Brushless DC Motor Drives

Bhim Singh,Sanjeev Singh 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.1

Permanent magnet brushless DC (PMBLDC) motors are the latest choice of researchers due to their high efficiency, silent operation, compact size, high reliability and low maintenance requirements. These motors are preferred for numerous applications; however, most of them require sensorless control of these motors. The operation of PMBLDC motors requires rotor-position sensing for controlling the winding currents. The sensorless control would need estimation of rotor position from the voltage and current signals, which are easily sensed. This paper presents state of the art PMBLDC motor drives with an emphasis on sensorless control of these motors.