Carrier Based Common Mode Voltage Reduction Techniques in Neutral Point Clamped Inverter Based AC-DC-AC Drive System

Amit Ojha,Pradyumn Chaturvedi,Arvind Mittal,Shailendra Jain 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Common mode voltage (CMV) generation is a major problem in switching power converter fed induction motor drive systems. CMV is the zero sequence voltage generated due to the switching action of power converters. Even a small magnitude of CMV with a high rate of change may circulate large bearing currents which may damage a machine’s bearings and shorten its life. There are several methods of controlling CMV. This paper presents 3-level sinusoidal pulse width modulation based techniques to control the magnitude and rate of change of CMV in multilevel AC-DC-AC drive systems. Simulation and experimental investigations have been presented to validate the performance of proposed technique to control CMV in 3-level neutral point clamped inverter based AC-DC-AC system.

Carrier Based Common Mode Voltage Reduction Techniques in Neutral Point Clamped Inverter Based AC-DC-AC Drive System

Ojha, Amit,Chaturvedi, Pradyumn,Mittal, Arvind,Jain, Shailendra The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Common mode voltage (CMV) generation is a major problem in switching power converter fed induction motor drive systems. CMV is the zero sequence voltage generated due to the switching action of power converters. Even a small magnitude of CMV with a high rate of change may circulate large bearing currents which may damage a machine's bearings and shorten its life. There are several methods of controlling CMV. This paper presents 3-level sinusoidal pulse width modulation based techniques to control the magnitude and rate of change of CMV in multilevel AC-DC-AC drive systems. Simulation and experimental investigations have been presented to validate the performance of proposed technique to control CMV in 3-level neutral point clamped inverter based AC-DC-AC system.

Anticipated Trajectory based Proportional Navigation Guidance Scheme for Intercepting High Maneuvering Targets

Amit Kumar,Aparajita Ojha,Prabin Kumar Padhy 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.3

Most of the existing target tracking schemes based on proportional navigation guidance laws requireinformation on target’s acceleration to device their tracking strategies. Acceleration is computed or estimated continuouslyat each step to guide the interceptor. However, computation of acceleration is time consuming and oftenleads to inaccuracy, especially when the target is high maneuvering. Keeping this in view, a proportional navigationbased guidance law for the interception of a high maneuvering target is presented that does not require estimationof the target’s acceleration to generate guidance command. The method is based on anticipating target’s trajectoryusing simple linear extrapolation and rotational correction. The interceptor predicts next position of the target andcontinuously adjusts its acceleration command to move towards the future position of the target. This simple modificationnot only helps in improving the time to intercept but also reduces number of target misses. Further, it iseasier to implement for real time applications due to computational convenience. Performance of the method iscompared with some of the most efficient navigation guidance laws with respect to the time taken in interception,distance traversed and the path followed by the interceptor. In addition, proof of convergence is provided. Simulationresults are further verified through hardware implementation on wheeled mobile robots and results are quiteencouraging.

Evaluation of mechanical and durability properties of con-crete made with Indian bottom ash as replacement of fine ag-gregate

P. N. Ojha,Amit Trivedi,Brijesh Singh,Abhishek Singh 아시아콘크리트학회 2020 Journal of Asian Concrete Federation Vol.6 No.2

Bottom ash is a major by-product of the coal-based power generation process and it has particle size ranging from 45 μm to 150 μm. As per current provisions of IS: 383-2016, bottom ash can be used as replacement of natural fine aggregate up to 25% in case of lean concrete (less than M15 Grade) only. However, its use in reinforced and plain concrete is not permitted. Therefore, it is imperative to study the feasibility of using coal based bottom ash as a replacement of conventional fine aggregates (i.e., natural and crushed sand) in plain and reinforced concrete to increase the utilization of this industrial byproduct. In this study, natural and crushed sand were replaced with bottom ash at various percent-ages for prepa-ration of concrete and study its effect on fresh, hardened and durability properties of concrete. Bottom ash was collected from Vindhyachal thermal power plant of India. Experimental studies were conducted at w/c ratio of 0.65 and 0.40. Concrete mixes were studied and analyzed for various mechanical and durability properties. Based on fresh concrete properties i.e., workability, slump retention and strength development, it was observed that up to 50% replacement of conventional fine aggregate with bottom ash is technically feasible.

Empirical equation and experimental validation of shear parameters for high strength concrete (HSC)

Brijesh Singh,Ojha P N,Patel Vikas,Trivedi Amit,Singh Abhishek 아시아콘크리트학회 2021 Journal of Asian Concrete Federation Vol.7 No.2

With many benefits of the high strength concrete (HSC) the more brittle behaviour that leads to sudden failure makes it important for proper understanding of its behaviour and safe and efficient estimation of capacities. Research on the behaviour of HSC has been extensively carried out since last decade. HSC has higher tensile strength hence a higher cracking shear can be expected. This paper analyzes the different international standards available for estimating concrete’s component of shear strength for reinforced cement concrete (RCC) beam. Different important factors mainly strength in compression, steel reinforcement (dowel action), ratio of shear span and depth, size effect i.e. depth along with the aggregate type (density of concrete) contributing to shear stress (Tc) of concrete has been also analyzed and thereafter, an equation has been proposed to compute or predict Tc value for concrete of both normal and higher grade or strength. The proposed equation has been validated by experimental results wherein 12 RCC beams (with and without reinforcement for shear) were cast and tested to fail in shear. The experimental results validated the proposed equation with considerable factor of safety keeping in view the sudden and brittle nature of failure in concrete in case of shear.

Perspectives for rare earth elements as feed additive in livestock - A review

Tariq, Hujaz,Sharma, Amit,Sarkar, Srobana,Ojha, Lamella,Pal, Ravi Prakash,Mani, Veena Asian Australasian Association of Animal Productio 2020 Animal Bioscience Vol.33 No.3

There is a need for newer feed additives due to legal prohibition on inclusion of growth promoting antibiotics in livestock diets in several countries due to antimicrobial resistance. In this context, rare earth elements (REE) have gained attention among animal nutritionists as potential growth promoters. Currently, several studies have reported better weight gain, milk production, egg laying capacity and feed conversion efficiency among different breeds of farm animals following supplementation with REE, with however largely inconsistent results. Furthermore, REE supplementation has also shown to improve ruminal fibrolytic and proteolytic activities as well as flavor of meat with negligible residues in edible tissue, however the mechanism behind this action is still unclear. According to existing research, due to their poor absorption and similarity with calcium REE might exert their action locally on gut microbial populations within the gastrointestinal tract (GIT). Moreover, REE have also shown anti-inflammatory, anti-oxidative as well as immune stimulating effects. The present review aims to broaden the knowledge about use of REE as feed additives for livestock and sum up efficacy of REE supplementation on performance and health of animals by comparing the findings. Till date, researches with REE have shown properties that make them a promising, new and safe alternative feed additive but further exploration is recommended to optimize effects and clarify discrepancy of various results before practical proposals can be drafted.