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In this paper, mathematically rigorous RL circuits of high-frequency multi-winding transformers are identified using an original three-step numerical procedure. They are composed of frequency-independent coefficients and can therefore be introduced in classical circuit simulators. First, the finite-element method in 3-D magnetodynamics, together with homogenization techniques which reduce the overall computational burden, are employed to extract frequency-dependent impedances and voltage gains. Then, the identified equivalent circuit is modified by removing the static resistances from the impedances, so as to obtain frequency-independent voltage gains, or coupling coefficients. An algorithm which is valid for any number of windings is proposed to that end. Finally, the frequency-dependent impedances are identified to Foster networks with constant elements using an optimization algorithm. An experimental validation with an impedance analyzer is proposed.

Electromagnetic launch systems consist of pulsed power, rectification, and launch components. The finite-element (FE) code EMAP3D is used to compute the fields diffusing into sliding electrical contact launch components using quasi-static field equations. FE analysis of the entire launch system, though not impossible, would be a time-consuming process not worth the effort. Circuit theory based on lumped parameters is better suited for the analysis of some of the electrical components such as the generator, rectifier, power conditioning, and delivery components. Circuit theory becomes almost inevitable when one seeks to maximize the power delivered to launch components through impedance tuning techniques. Hence, one is inclined to look at ways of analyzing entire launch systems applying circuit theory to some components and FE analysis to others where detailed fields are required. An algorithm to couple an external circuit with an applied potential difference and prescribed resistances and inductances with a simple railgun is presented in this paper. The railgun is analyzed using EMAP3D. The external circuit is treated using circuit theory. Continuity of current and potentials is maintained through iterative calculations matching the currents and potentials between the circuit and the railgun. The advantages of this algorithm are that it treats the components using circuit theory and field theory separately and shows rapid convergence

The design and equivalent circuit of an inductor with a ferromagnetic film is described. High-frequency circuit simulation including inductance is carried out by two methods: 1) a SPICE-based simulation in which the distributed linear circuit is converted into a GCRL equivalent circuit and 2) an harmonic balance method in which the nonlinear active part of the circuit is solved in terms of sinusoidal harmonics in the frequency domain. High-frequency circuits including inductors and active elements such as low noise amplifiers are analyzed by these methods.

This paper presents an analytic solution for the transient response of a parallel RL network with piecewise linear inductance. It compares the rise time and zero-crossing pulse compression of the nonlinear network with a corresponding linear network. It shows that there is a rise time and compression improvement in the nonlinear circuit as the amplitude of the input current increases. It provides analytic expressions as well.

The Jiles-Atherton (J-A) model is applied to the problem of describing the dynamics of a nonlinear circuit driven by a square wave voltage source and comprising a linear resistor and capacitor in series with a nonlinear inductor, whose core displays saturation and hysteresis. The presence of hysteresis is shown to increase the order of the circuit by one. Period-multiplication and chaos are observed and excellent agreement is obtained between experiment and simulation. >

New zero-dimensional or scalar electromagnetic finite elements, that have the time integral of electric scalar potential as their nodal variable are presented. There are three zero-dimensional element types, representing resistors, capacitors, and inductors. These elements can be easily combined with two- or three-dimensional elements, with three components of magnetic vector potential and the time integral of electric scalar potential as nodal variables. Constant current sources are directly modeled by inhomogeneous Neumann excitations, and constant voltage sources are modeled by use of Norton's theorem. By the addition of dependent current and voltage sources, electronic circuits can be modeled. Example finite-element analyses include an R-L circuit, a transistor circuit driving a wire loop modeled with three-dimensional finite elements, and a circuit impedance on the secondary of a saturable three-dimensional transformer model. >

This paper describes the operating characteristics of a new reactor circuit using an inductance, a transformer and a resistance. The reactor circuit utilizes both the line and phase voltages of three-phase voltage source, and can reduce the 5th harmonic component of output voltage by changing the value of resistance connected to the transformer. An application of the reactor circuit to a filter circuit to remove the 5th harmonic voltages of three-phase source is presented in this paper.

The authors describe the operating characteristics of an oscillating circuit using a bridge-connected magnetic circuit and another magnetic core. A square-shape output voltage is obtained in the oscillating circuit. The pulsewidth in positive and negative half cycles of output voltage changes with the current of the U-form core windings and with the signal voltage applied to the exciting windings. The mean value of the output voltage varies in proportion to the product of the current and the signal voltage. Utilizing this feature, an application of the oscillating circuit to a novel power measuring circuit of simple construction is presented. >

In the pulse charging and discharging of energy storage inductors, the influence of I2R heating, magnetic diffusion skin depth, and eddy current losses must be evaluated. These effects are not easily treated analytically. To address these problems, the system can be constructed according to governing scaling laws. The performance of the model can then be evaluated and scaled up to predict actual system performance. The scaling laws as applied to a 1O-MJ homopolar generator charging a 2-MJ cryogenic aluminum Brooks coil are presented in this paper. System parameters measured on the scale model are compared to parameters subsequently measured on the full-size equipment.

A method has been developed for determining the current time constant τ at which eddy currents become detrimental to electromagnet operation. Plots of flux density B versus time, and current I versus time were made for various values of τ on electromagnets having a constant air gap and a fixed value of maximum current I m in the coil. Such an electromagnet can be approximated by a linear RL circuit as long as eddy current effects are negligible. τ was the time required for the current to reach 0.63 I m . This corresponds to the time constant in a linear RL circuit. Values of dB/dt were measured at τ and the relationship dB/dt = C/\tau^{m} , where m equals 1 and C is a constant, was found to be applicable for large values of τ, as expected in a linear RL circuit. The τ value τ c at which m began to decrease from 1, determined the onset of eddy current effects since the circuit is no longer linear. Experimental results were compared to a theoretical solution for a ramp field applied to sheets of thickness δ. Calculations were performed of the time \Deltat by which the flux density lags the applied field. Reasonably good correlation was obtained between \Deltat and τ c . Measurements were made on various soft magnetic materials in various thicknesses. The results provide a guide in selecting material and lamination thickness for a given application.

By use of the Neeteson approximation, design equations are developed from which the irreversible switching characteristics of a magnetic core working into a series RL load are predicted by numerical calculations.