Zivan Zabar

Mutual inductance of noncoaxial circular coils with constant current density

The purpose of this paper is to determine the mutual inductance between two noncoaxial circular coils. In many cases, such as coil guns or tubular linear motors, one of them is fixed while the other one is moving, and if not supported, its axis may not coincide with that of the fixed coil. This paper presents a method for the calculation of the mutual inductance in the case of noncoaxial coupled coils, the characteristics of this inductance, and experimental results. The computation is based on complete elliptic integrals and on the mesh-matrix technique. The method enables one to obtain accurate results from a relatively simple procedure and calculation program.

Analysis of Voltage Profile Problems Due to the Penetration of Distributed Generation in Low-Voltage Secondary Distribution Networks

This paper presents a comprehensive analysis of the possible impacts of different penetration levels of distributed generation (DG) on voltage profiles in low-voltage secondary distribution networks. Detailed models of all system components are utilized in a study that performs hundreds of time-domain simulations of large networked distribution systems using the Electromagnetic Transients Program (EMTP). DGs are allocated in a probabilistic fashion to account for the uncertainties of future installations. The main contribution of this paper is the determination of the maximum amount of DG that secondary distribution networks can withstand without exhibiting undervoltage and overvoltage problems or unexpected load disconnections. This information is important for network planning engineers to facilitate the extension of the maximum penetration limit. The results show that depending on the location, type, and size of the installed DGs, small amounts of DG may cause overvoltage problems. However, large amounts of DG may not cause any voltage problems when properly selected.

Experimental Determination of the ZIP Coefficients for Modern Residential, Commercial, and Industrial Loads

This paper presents the experimental determination of the ZIP coefficients model to represent (static) modern loads under varying voltage conditions. ZIP are the coefficients of a load model comprised of constant impedance Z, constant current I, and constant power P loads. A ZIP coefficient load model is used to represent power consumed by a load as a function of voltage. A series of surveys was performed on typical residential, commercial, and industrial customers in New York City. Household appliances and industrial equipment found in the different locations were tested in the laboratory by varying the voltage from 1.1-p.u. voltage to 0 and back to 1.1 pu in steps of 3 V to obtain the individual P- V, Q- V, and I- V characteristics. Customer load tables were built using seasonal factors and duty cycles to form weighted contributions for each device in every customer class. The loads found in several residential classes were assembled and tested in the lab. It was found that modern appliances behave quite differently than older appliances even from only 10 years back. Models of the different customer classes were validated against actual recordings of load variations under voltage reduction.

Analysis of induction-type coilgun performance based on cylindrical current sheet model

A method which is based on a cylindrical current sheet model for the analysis and design of induction-type coilguns is presented. The work starts with a derivation of closed-form formulae which relate the dimensions of the gun to the performance expressed in terms of propulsive and local maximum forces on the projectile, power factor and efficiency of the system, thermal stress of the projectile armature, distributions of the flux density around the launcher, and the system parameters in a multisection coilgun. A numerical example is given. >

Concerning the design of capacitively driven induction coil guns

The authors consider the design of capacitively driven, multisection, electromagnetic coil launchers, or coil guns, taking their transient behavior into account. A lumped-parameter computer simulation is developed to predict the performance of the launcher system. It is shown that a traveling electromagnetic wave can be generated on the barrel by the resonance of drive coils and their capacitors. More than half of the energy initially stored in the capacitor bank can be converted into kinetic energy of the projectile in one shot, and an additional quarter can be utilized in subsequent shots, if the launcher dimensions, resonant frequency, and firing sequence are properly selected. The projectile starts smoothly from zero initial velocity and with zero initial sleeve current. Section-to-section transitions which have significant effects on the launcher performance are also discussed. Experimental results were obtained with a small model and are in good agreement with theoretical predictions. >

Voltage flicker mitigation using PWM-based distribution STATCOM

Voltage flicker, a phenomenon of annoying fight intensity fluctuation, caused by large rapid industrial load changes, has been a major concern for both power companies and customers in the area of power quality. The fast response of the distribution static compensator (DSTATCOM) makes it the efficient solution for improving power quality in distribution systems. In this paper, a voltage flicker phenomena in a 69/13.8 kV distribution system Is modeled and simulated using MATLAB/Simulink Power System Blockset (PSB). Voltage flicker mitigation studies with a current controlled PWM-based DSTATCOM are also performed and discussed.

Design and power conditioning for the coil-gun

The author describes the power conditioning scheme for a contactless coilgun called the linear induction launcher (LIL). The barrel of the LIL consists of a linear array of coils carrying polyphase currents. These create an electromagnetic wave pocket which moves with increasing velocity from breech to muzzle, smoothly accelerating a conductive sleeve which carries a set of azimuthal currents sinusoidally distributed along its length and which encloses the projectile payload. The power conditioner provides high energy utilization by transferring energy from capacitor to capacitor simultaneously with the projectile movement. The modular construction of the barrel is described together with laboratory results obtained with a breadboard model of the power conditioner circuit. >

Restoring force between two noncoaxial circular coils

Considered here are the forces between two current-carrying circular coils, one of which, the primary coil, has a larger diameter than the other, the secondary. In the case in which the secondary coils central axis does not coincide with that of the primary, there exists a transverse force which we call the restoring force. It is found that this force decreases with increasing distance between the coils and changes sign. This paper presents a calculation of this force and its characteristics. Finally, it introduces some experimental results.

A Novel Magnetic-Levitation System: Design, Implementation, and Nonlinear Control

This paper concerns the design, implementation, and nonlinear velocity-tracking control of a novel magnetic-levitation (maglev) system for magnetically levitated trains. The proposed system uses only one tubular linear induction motor to produce three forces required in a maglev system: propulsion, levitation, and guidance. Classical maglev systems, on the other hand, contain a separate force-generating system to build each of these three forces. Another benefit that the proposed system offers is that there is no need to control the guidance, and particularly, the levitation forces, one of the most challenging tasks in maglev systems. The system always centers the moving part during operation and eliminates the necessity for control of the levitation and guidance forces. However, the propulsion force strongly requires some control efforts because a linear induction motor has nonlinear system dynamics. This paper gives a condensed design guideline based on the mature theory of electromagnetic launchers, particularly the linear induction launcher type. It explains the implementation process, shows experimental test results, and finally, presents a nonlinear partial state-feedback controller for the proposed system.

On the Transient Behavior of Large-Scale Distribution Networks During Automatic Feeder Reconfiguration

The paper presents an in-depth analysis of the automatic reconfiguration and self-healing principles of the next generation (3G) smart grid of a real metropolitan distribution network. The large network is to be divided dynamically and remotely controlled into three smaller subnetworks to further increase the reliability of electrical power distribution secondary networks. When one subsection is experiencing difficulties, there is no longer the need to de-energize the entire network. A time-domain (EMTP) model has been developed and validated by comparing simulations with recordings of actual transient events. Different switching and fault scenarios are investigated using this model. Analysis of the results provides important conclusions on equipment rating, relay protection coordination, voltage regulation, switching and operation strategies which are discussed in the paper. A subset of these results is presented for illustration. This extensive study of a complex urban network suggests that: 1) before implementation of smart grid principles, it would be prudent to supplement steady-state analysis with time-domain analysis to avoid problems, such as installation of improperly rated equipment, and improper relay-protection coordination; and 2) EMTP-type programs may be used to conduct the time-domain analysis, despite the enormous number of elements contained in an urban network.