13 research outputs found

    Electric otors and Drives in Torsional Vibration Analysis and Design

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    TutorialTwo types of prime movers are continuously applied for rotating machinery: mechanical and electric drives. This tutorial focuses on electric drives, which are actually composed of separate components: electric motor, frequency converter (optional), and electric network including transformers. The main aim of this tutorial is to explain the phenomena of electric drives related to the torsional vibrations. All the components of an electric drive may affect torsional dynamics of the system. Naturally the main concern is torsional excitations. Another aspect is the electromechanical interaction in the air-gap of the motor that produces electromagnetic torsional stiffness and damping. These and other similar phenomena, related to the electric drives, have been observed on test fields and site conditions. The scope of the paper includes the most common induction, synchronous and permanent magnet motors. First, the various rotor structures of electric motors are discussed. Then, the effects of electromagnetic stiffness and damping on the torsional dynamics are introduced. Next, the main electric excitations are presented and their effect on drivetrain dimensioning is discussed. Various modelling and analysis methods are also presented for drive-trains with an electric motor. The previous sections focus on the motor without any frequency converter. The rest of the paper deals with the variable speed drives. First the main voltage source inverter, current source inverter and load commutated inverter drive types, their operational principles and application areas are introduced. Then the harmonic and inter-harmonic torsional excitations are explained that depend on the configuration and control of the frequency converter. The main functionality of a variable speed drive system is the speed-control feedback loop. This loop is used to maintain the preset speed. Although this feedback loop is also a potential source of instability it can with proper tuning be used to damp low frequency torsional resonances. The analysis guidelines and design principles are distributed throughout the paper. The paper is concluded with summary and main recommendations

    Charging Station for Electric Bikes Powered by Renewable Energy

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    This report serves the purpose to answer the research problem of developing a charging station for electric bicycles powered by renewable energy allowing rental companies to create a safer and more sustainable way of commuting. The report was divided into a business and a mechanical part to provide a better overview of each area of operations. The business part focuses on the establishment of the company, SolHavn, the analysis of market environment and customers, as well as the creation of a suitable marketing strategy, and the projection of the expected financial positioning of the company. On the other hand, the mechanical part demonstrates the correct and accurate method to dimension and design a solar charging station that capable of charging 10 electric bike according to appropriate mechanical calculation, assumption and analysis realized. The value of the energy consumption was estimated for the off-grid situation primarily and it mainly focus on the worst case scenario season in Barcelona, Spain. Moreover, the consideration of losses that would happen in electrical cabling and other electronic related component like step-down, charge controller and other was taken into account. Finally, the structural design for the station as demonstrated and would be able to support the load of chosen solar panel and other natural loads after detailed calculation. Besides, other simulation which involved other scenario like hybrid and on-grid was considered and analyzed. The comparison between these other scenarios helped in improving the solar station for further project.<br /

    Automated hybrid solar and mains system for peak time power demand.

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    Master of Science in Electrical Engineering.The power demand during peak period causes large power fluctuations in the commercial grid. The reduction in using grid supply during peak time benefits the supplier and consumer. There are many methods such as monitoring the usage of grid supply, load shedding, using local generators and disconnecting unwanted loads during peak time used to reduce grid dependency during peak time. These methods reduce power demand from grid by either supplying interrupted power to the load or by establishing additional power source. In South Africa, solar energy is abundantly available and it can be utilized to solve the power demand during peak time. In this research, solar and grid power are chosen as two power sources and automatic switching system to select the power source to supply uninterrupted power to the load is designed. The important aspect of using solar system is estimating the system output. The maximum power point tracking system using perturb and observe algorithm is designed. The boost converter and inverter circuits are designed to supply power to the coffee shop loads at Howard College Campus. Battery charger circuit is designed to charge the battery from solar or grid and supply power to the load whenever required. The switching algorithm connects the load to solar or battery during peak time and connects it to grid during off peak time. The switching algorithm is designed to supply uninterrupted power to the load by connecting it to available source when any one of the source failure occurs. The power output from the panel is maximized by automatic panel cleaning system. The panel cleaning starts at the pre-programmed schedule and provision for manual override option to reschedule panel cleaning operation is also provided. The designed system is tested in MATLAB and Proteus simulation software. The results of each section are discussed. It can be seen that designed automatic selection of power sources for supplying 1kW of power during peak time to the selected coffee shop considerably reduces the cost and power demand from the grid during peak time. The designed system is economically feasible and efficient in supplying uninterrupted power to the load

    Establishing a Comprehensive Wind Energy Program

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    Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 1

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    Papers from the technical sessions of the Technology 2001 Conference and Exposition are presented. The technical sessions featured discussions of advanced manufacturing, artificial intelligence, biotechnology, computer graphics and simulation, communications, data and information management, electronics, electro-optics, environmental technology, life sciences, materials science, medical advances, robotics, software engineering, and test and measurement

    NREL Photovoltaic Program FY 1995 annual report

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    Extended Modulus Optimum Method for Off-Grid Inverter's Voltage Control System

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    Stationary reference frame proportional-resonant (PR) controllers play a significant role in grid-tie and off-grid inverter control because of their ability to achieve zero steady-state error at AC frequency and provide high rejection ratio for undesirable harmonic content with minimum computation burden. While extensive efforts have been put into application-oriented performance optimization for grid-tie application, the off-grid inverter case was barely investigated. This paper proposes an extension of the Modulus Optimum tuning method from a synchronous frame to a stationary frame. The proposed approach is directly applied to the transfer function of the off-grid inverter in a stationary frame. As a result, the structure of the controller with optimized transient and steady-state behaviours is synthesized. The relationship between the proportional and the resonant part of the investigated controller is obtained to achieve the optimum utilization of the presented control bandwidth. The validation of the presented approach was performed by computer simulations and laboratory experiments on the off-grid battery inverter

    Acta Universitatis Sapientiae - Electrical and Mechanical Engineering

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    Series Electrical and Mechanical Engineering publishes original papers and surveys in various fields of Electrical and Mechanical Engineering
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