1,721,848 research outputs found
Lectotypification of four names in the genus Smilax (Smilacaceae)
No full textSukhramani, Geetika, Choudhary, Ritesh Kumar (2022): Lectotypification of four names in the genus Smilax (Smilacaceae). Phytotaxa 532 (1): 107-113, DOI: 10.11646/phytotaxa.532.1.1
Bringing Capparis zeylanica (Capparaceae) out of chaos: nomenclatural updates and amended description
No full textMaurya, Satish, Choudhary, Ritesh Kumar (2021): Bringing Capparis zeylanica (Capparaceae) out of chaos: nomenclatural updates and amended description. Phytotaxa 528 (4): 263-268, DOI: 10.11646/phytotaxa.528.4.
Canscora ciathula is not Canscora but rather belongs to the genus Phyllocyclus
No full textSarawgi, Aditi, Choudhary, Ritesh Kumar (2022): Canscora ciathula is not Canscora but rather belongs to the genus Phyllocyclus. Phytotaxa 575 (2): 184-186, DOI: 10.11646/phytotaxa.575.2.9, URL: http://dx.doi.org/10.11646/phytotaxa.575.2.
Electric Vehicle Propulsion System
Full text linkElectric vehicles are being considered as one of the pillar of eco-friendly solutions to overcome the problem of global pollution and radiations due to greenhouse gases. Present thesis work reports the improvement in overall performance of the propulsion system of an electric vehicle by improving autonomy and torque-speed characteristic. Electric vehicle propulsion system consists of supply and traction system, and are coordinated by the monitoring & control system. Case of light electric vehicle propulsion system with permanent-magnet (PM) brushless dc (BLDC) drive being used in electric scooters and electric-mini cars is considered for analytical study and the implementation of the proposed solutions. PM BLDC motor and voltage source inverter are considered as a part of traction system and electric energy source such as battery, fuel cell or photovoltaic panel are considered as a part of supply system.
Available electric energy sources are capable of delivering higher current at lower terminal voltage, so are connected either in series or -more often- to the higher voltage dc-link through a circuital arrangement (boost topology) to achieve higher voltage. For the evaluation of boost topologies, traditional dc-to-dc boost converter with cascade VSI (DBI) and Z-source inverter (ZSI) are considered for fuel cell and battery as on-board energy sources. Evaluation of the convenience of the two supply topologies is carried out in terms of the factors defining transistor power utilization, and voltage and current transistor solicitation. In addition to mentioned defined factors, sizing of the passive components in terms of the power contribution factor of fuel cell is considered. In respect to the defined factors, DBI supply is found to be beneficial for PM BLDC drive whereas, with respect to the power contribution factor, ZSI supply is good to adopt for the cases were major contribution of power is from battery.
For the improvement in torque-speed characteristics of the considered drive, issue of torque ripple due to non-ideal phase commutation in case of conventional square-wave phase current (SqPC) supply is studied analytically by establishing a correlation between the behavior of the commutating phase currents and motor torque. Behavior of the motor torque during commutation for low and high speed zone as a function motor speed and defined motor specific quantity are explained in detailed. The analytical results are used to explain the dropping torque-speed characteristic of the drive and are verified experimentally for a propulsion drive available in the laboratory. Dropping torque-speed characteristic limits the use of the drive up till the nominal speed. To overcome this issue sinusoidal phase current (SPC) supply is proposed. SPC offers constant motor torque. A detailed convenience analysis of SPC over SqPC is carried out. Strategy for the implementation of SPC supply is also discussed and the analytical results were verified by the experimentally.
The study of the PM BLDC drive by means of the space phasor/vector approach has been executed. While such an approach is quite common for drives with motors with sinusoidal back-emf and phase currents, it is not explored in the literature for the present case, where back-emfs are trapezoidal and phase currents are square-wave in nature. Behavior of the PM BLDC drive has been revisited in stationary plane and the current commutation between the motor phases has been explained with the help of phase variable vectors. All the results obtained in a-b-c plane are cross verified in stationary plane showing the simplicity and potentialities of the vector approach for PM BLDC drive.
To address the issue of the autonomy of electric vehicles, use of solar energy to assist the on-board batteries of an electric mini-car is considered. Photovoltaic Geographical Information Systems database provided by Joint Research Centre Europe, is used to estimate the solar irradiance available in Padova, Italy. Output of a 0.487 sq-meter, 20-cell multi-crystalline PV panel is estimated and accordingly a conventional dc-to-dc boost converter is designed to interface PV panel with dc-link of a mini-car available in the laboratory. Appropriate control is implemented through DSP to track maximum power point. Whole system was tested outside the laboratory and measurements were carried out. Analytical loss model of the dc-to-dc boost converter is developed to explain the variations in gain, efficiency and loss components of the converter under varying solar irradiance.
The thesis work has been carried out at the Laboratory of “Electric systems for automation and automotive” headed by Prof. Giuseppe Buja. The laboratory belongs to the Department of Industrial Engineering of the University of Padov
FIGURE 1 in Bringing Capparis zeylanica (Capparaceae) out of chaos: nomenclatural updates and amended description
No full textFIGURE 1. Second step lectotype of Capparis zeylanica L. (BM000621009) ©BMPublished as part of Maurya, Satish & Choudhary, Ritesh Kumar, 2021, Bringing Capparis zeylanica (Capparaceae) out of chaos: nomenclatural updates and amended description, pp. 263-268 in Phytotaxa 528 (4) on page 264, DOI: 10.11646/phytotaxa.528.4.6, http://zenodo.org/record/579490
FIGURE 2 in Lectotypification of four names in the genus Smilax (Smilacaceae)
No full textFIGURE 2. Lectotype of Smilax kingii J.D.Hooker K000292116 © copyright of the Board of Trustees of the Royal Botanic Gardens, Kew.Published as part of Sukhramani, Geetika & Choudhary, Ritesh Kumar, 2022, Lectotypification of four names in the genus Smilax (Smilacaceae), pp. 107-113 in Phytotaxa 532 (1) on page 109, DOI: 10.11646/phytotaxa.532.1.10, http://zenodo.org/record/590079
FIGURE 1 in Canscora ciathula is not Canscora but rather belongs to the genus Phyllocyclus
No full textFIGURE 1. Holotype of Canscora ciathula Aver. (AL 785, barcode LE 01048221) ©LE.Published as part of Sarawgi, Aditi & Choudhary, Ritesh Kumar, 2022, Canscora ciathula is not Canscora but rather belongs to the genus Phyllocyclus, pp. 184-186 in Phytotaxa 575 (2) on page 185, DOI: 10.11646/phytotaxa.575.2.9, http://zenodo.org/record/741329
Lectotypification of four names in the genus Capparis (Capparaceae)
No full textMaurya, Satish, Datar, Mandar N., Choudhary, Ritesh Kumar (2021): Lectotypification of four names in the genus Capparis (Capparaceae). Phytotaxa 500 (2): 125-132, DOI: 10.11646/phytotaxa.500.2.5, URL: http://dx.doi.org/10.11646/phytotaxa.500.2.
Certificate
No full textThis is to certify that the thesis titled “A Framework for Multimedia Streaming over WiMAX in an Emerging Market Scenario ” being submitted by Mr. Ritesh Kumar K to the International Institute of Information Technology, Bangalore, for the award of the Degree of Master of Technology, is a record of bonafide research work carried out by him under our supervision, and Mr. Ritesh Kumar K fulfills the requirements of the regulations of the degree. The contents of this thesis have not been submitted to any other university or institute for the award of any degree or diploma
Vector analysis of the current commutation in PM BLDC drives
Full text linkThe vector approach in either stationary or synchronous plane is commonly used for the analysis of the AC drives like induction and PM brushless AC drives whilst it has been hardly ever used for the PM brushless DC (BLDC) drives. A possible reason is that they require injection of square-wave currents into the motor phases, which are non-sinusoidal in nature. Recently, the PM BLDC drives have been analyzed by the help of the vector approach in the stationary plane. This paper applies such an approach to an in-depth analysis of the operation of the PM BLDC drives during the current commutations, illustrating the potentialities of the approach in giving a better insight into the current transients and the ensuing torque characteristics. At last, two voltage control strategies proposed to eliminate the torque ripple due to the current commutations are considered, showing that they can be readily understood by the vector approach
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