Faculty Publications
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Publications by NITK Faculty
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Item Finite element method magnetics based demonstration of rotating field in 4-pole induction motor(2013) Punekar, G.S.; Devarajan, D.; Tantry, G.H.The explanation related to the concept of Rotating Magnetic Field (RMF) in 3-phase induction motor (IM) and its visualization is a tricky issue in teaching-learning process. The complexity increases with the number of poles. Hence visualization of RMF for a 4-pole Induction motor is attempted via magnetic field distribution pattern(s). The aim of this paper is to explore and utilize the capability of Finite Element Method Magnetics (FEMM) as a tool for demonstrating rotating magnetic field effect produced in the stator of a 3-phase induction motor. In addition to the RMF demo, visual correlation between angular rotations of electrical wave with mechanical degree is reported. Also, the effect of phase sequence reversal is incorporated in the graphical exhibition. © 2013 Springer.Item Motor contribution to three phase fault currents in a power intensive industry with CPP: A case study(Institute of Electrical and Electronics Engineers Inc., 2018) Kotharkar, A.A.; Punekar, G.S.Addition of motor-contribution to the total fault current during a three-phase fault is of interest to all power intensive industries with dominant motor loads. Such results are analyzed for a petrochemical industry where majority of loads are induction motors. Three phase fault currents are computed at five buses of 6.6 kV and also at the main distribution bus of 33 kV. In this case study, the fault currents at 6.6 kV buses are estimated due to the contributions from (i) captive generating units alone (ii) motor(s) connected to the faulty bus only (to that of generating units) (iii) all the major motors in the network including those connected to faulty bus (to that of generating units). The results indicate that for this industry, with captive generation, the motor-contribution to fault currents can be as high as 40%. The transformer rating (and its impedance) feeding the motors play an important role in the motor-contributions to fault currents. © 2018 IEEE.Item A novel CSI-fed induction motor drive(2006) Beig, A.R.; Ranganathan, V.T.Current source inverter (CSI) fed drives are employed in high power applications. The conventional CSI drives suffer from drawbacks such as harmonic resonance, unstable operation at low speed ranges, and torque pulsation. This paper presents a novel CSI drive which overcomes all these drawbacks and results in sinusoidal motor voltage and current even with CSI switching at fundamental frequency. The proposed CSI drive uses a three-level inverter as an active filter across motor terminals replacing the bulky ac capacitors used in the conventional drive. A sensorless vector controlled CSI drive based on proposed configuration is developed. The simulation and experimental results are presented. Experimental results show that the proposed drive has stable operation even at low speeds. Comparative results show that the proposed CSI drive has improved torque ripple compared to the conventional configuration. © 2006 IEEE.Item Modified SVPWM algorithm for three level VSI with synchronized and symmetrical waveforms(2007) Beig, A.R.; Narayanan, G.; Ranganathan, V.T.The objective of the present work is to improve the output waveform of three level inverters used in high-power applications, where the switching frequency is very low. This is achieved by maintaining the synchronization, half-wave symmetry, quarter-wave symmetry, and three-phase symmetry in the pulsewidth modulation (PWM) waveforms. The principles of achieving synchronization and symmetries in terms of space vectors for three level inverters are presented. A novel synchronized space vector pulsewidth modulation (SVPWM) algorithms is proposed and verified experimentally. The experimental waveforms of the inverter output voltage and motor no load current for different operating conditions of the drive are presented. The performance measure in terms of the weighted total harmonic distortion (THD) of the line voltage is computed for the linear modulation region of the drive for the proposed algorithm and compared with that of synchronized SVPWM and synchronized sine-triangle pulsewidth modulation (SPWM) technique. The comparative results show that consideration of synchronization and symmetry results in improved THD. Another significant feature of the proposed algorithm is that the symmetry and synchronization leads to self-balancing of the direct current (dc) bus capacitor voltages over every one third cycle of the fundamental. © 2007 IEEE.Item Synchronized symmetrical bus-clamping PWM strategies for three level inverter: Applications to low switching frequencies(2011) Veeranna, S.B.; Yaragatti, U.R.; Beig, A.R.The digital control of three-level voltage source inverter fed high power high performance ac drives has recently become a popular in industrial applications. In order to control such drives, the pulse width modulation algorithm needs to be implemented in the controller. In this paper, synchronized symmetrical bus-clamping pulse width modulation strategies are presented. These strategies have some practical advantages such as reduced average switching frequency, easy digital implementation, reduced switching losses and improved output voltage quality compared to conventional space vector pulse width modulation strategies. The operation of three level inverter in linear region is extended to overmodulation region. The performance is analyzed in terms THD and fundamental output voltage waveforms and is compared with conventional space vector PWM strategies and found that switching losses can be minimized using bus-clamping strategy compared to conventional space vector strategy. The proposed method is implemented using Motorola Power PC 8240 processor and verified on a constant v/f induction motor drive fed from IGBT based inverter. © 2011 Berkeley Electronic Press. All rights reserved.Item Comprehensive study of mixed eccentricity fault diagnosis in induction motors using signature analysis(2012) Rajalakshmi Samaga, B.L.; Vittal, K.P.Modeling and simulation studies of an induction motor always help in identifying the parameter to characterize the asymmetrical fault in the machine. Hence in this paper, an air gap eccentric induction motor is modeled using multiple coupled circuit approach and 2D-Modified Winding Function Theory. The machine model is simulated under different eccentricity conditions to obtain the motor current spectra, power spectra and power factor spectra to detect the eccentricity related frequency components and the results are compared. All these analysis are based on the variation in the amplitude of mixed eccentricity related frequency component in these parameters with the variation in the level of eccentricity in the machine. A new fault severity detection method based on co-variance analysis is presented to predict the degree of deterioration in the health of the machine due to air gap eccentricity from the installation stage. © 2011 Elsevier Ltd. All rights reserved.Item Direct torque controlled induction motor drive based on cascaded three two-level inverters(Acta Press, 2014) Thippiripati, T.V.; Surapaneni, S.S.In this paper, a new and an effective voltage switching-state algorithm to Direct Torque Control (DTC) of induction motor drive is proposed, which makes less torque and flux ripple at various operating frequency conditions. In conventional DTC, the torque and flux ripples are difficult to reduce as the applied voltage vector is independent of rotor speed especially at low speeds. To overcome this problem, the proposed technique introduces a voltage switching-state algorithm for four-level inversion using cascading three two-level inverters, in which choice of inverter voltage states is the function of rotor speed. From simulation results, the torque and flux ripple are decreased with proposed DTC when compared with the conventional DTC technique at various operating frequencies.Item Effect of Partial Shading on PV Fed Induction Motor Water Pumping Systems(Institute of Electrical and Electronics Engineers Inc., 2019) Mudlapur, M.; Ramana, V.V.; Damodaran, R.; Balasubramanian, B.; Mishra, S.Partial shading is one of the certain conditions in photovoltaic (PV) power plants. Often the panels get partially shaded due to soiling, clouds, and trees. The effect of shading is of high concern and importance especially in applications such as water pumps due to agricultural environments in which they are employed in. However, the research focus on PV fed pumps till date has been restricted to only uniform shading conditions. Unlike uniform shading conditions during maximum power tracking, where the panel voltage remains almost constant for an entire range of irradiance, partial shading offer conditions such as highly variable panel voltage and transitions of intermediate DC-DC power converter from continuous conduction mode to discontinuous conduction mode. These effects severely affect the performance of the power converter and, therefore, the power output of the pump. This paper presents a study on the effects caused by partial shading conditions on pumps through simulations and verified by experimentations. The simulation and experimental results are found to be in good agreement with each other. This research thus helps in understanding the detrimental effects caused by partial shading conditions and thus serves as a reference tool for practitioners who wish to study PV fed pumps. © 1986-2012 IEEE.Item Characterization of Fault Signature Due to Combined Air-Gap Eccentricity and Rotor Faults in Induction Motors(Praise Worthy Prize S.r.l, 2021) Bindu, S.; Sumam David, S.; Thomas, V.V.An accurate means of non-invasive condition monitoring of the popular industrial drive, three-phase squirrel-cage induction motor, can help to avoid unscheduled maintenance downtime and loss. Faults like air-gap eccentricity can exist even in a newly assembled drive and hence may co-exist with other internal defects. Despite it being a possible situation, the occurrence of simultaneous faults has seldom been studied. Therefore, there is a need for identifying fault signatures of combined fault conditions in a non-invasive manner. This paper presents a detailed model-based study on a three-phase squirrel-cage induction motor with the simultaneous existence of broken rotor-bar and air-gap mixed eccentricity faults using spectral analysis of stator current, instantaneous power, and estimated air-gap torque signals. The modelling of the machine is done using the Multiple Coupled Circuit method and modified to model the presence of the combined fault conditions. A comparative evaluation with various fault conditions and their severity is carried out by spectral analysis, and unique slip-dependent frequency components are identified in the spectra of diagnostic signals. This fault characterization is the most significant contribution of this paper. © 2021 Praise Worthy Prize S.r.l.-All rights reserved.Item An effective standalone hybrid wind-photovoltaic water pumping system with reduced power converter count(John Wiley and Sons Ltd, 2021) Angadi, S.; Yaragatti, U.R.; Yellasiri, Y.; Raju, A.B.This article proposes a standalone hybrid wind-photovoltaic (PV) water pumping system (WPS) with minimal power electronics interface, simple composite control, and optimal energy management strategy (EMS) for effective utilization of both renewable sources. The proposed system consists of classic Perturb and Observe (P&O) algorithm applied to the boost converter of the solar PV system and voltage regulation algorithm/hill-climbing MPPT algorithm with zero steady-state oscillation (ZSSO) applied to bidirectional voltage source converter (VSC) of wind energy conversion systems (WECS) for optimal power extraction at all times. The constant voltage to frequency (V/F) ratio is ensured at the point of common coupling (PCC) for the entire operating range to avoid saturation in the self-excited induction generator (SEIG) and the induction motor (IM) pump. The energy management strategy is devised to effectively harness renewable energy from both sources while ensuring the DC-link voltage stability. The system forms compelling proposition, given the least converter count to integrate solar-PV and wind energy employing easy to implement control algorithms with optimal energy extraction. The results of simulation and experimental studies on the proposed system reveal the effectiveness of the composite controller in terms of energy utilization, constant flux operation, and power balance for the entire operating range. Additionally, system exhibits acceptable dynamic and steady-state behavior against variations in wind velocity, solar irradiation, and load. © 2021 John Wiley & Sons Ltd.