Paul P. Biringer

High-frequency operation of a planar-type microtransformer and its application to multilayered switching regulators

The operation of a multilayered microtransformer composed of planar zig-zag coils and amorphous magnetic film is described. The transformer has a maximum efficiency of 77.5%. Its equivalent circuit is approximated by the parallel connection of the winding inductance and of the stray capacitance. Variable magnetic coupling is obtained between the primary and secondary windings by shifting the relative position of the two coils. The microtransformer is used in a magnetically controlled multilayered switching regulator. The regulator has an output of 1.4 W and an efficiency of 24%. The magnetization loss in the circuit is the same as that of the semiconductors. A two-output-type multilayered switching regulator is also proposed that has an acceptably good output characteristic at each port even though a common magnetic film is used. >

Eddy-current power loss in toroidal cores with rectangular cross section

In this paper, we investigate eddy-current power loss in toroidal cores with a rectangular cross section. An analytical method is used in which the field variables are expressed in terms of products of Bessel functions and trigonometric functions. A closed-form expression is derived for the power loss. The influence of various parameters such as skin depth and core dimensions over a wide range is discussed. Simplified expressions for the power loss at special cases such as very small and very large skin depths are provided. A comparison with measured values is presented.

Static frequency changers

Static magnetic frequency changers gained wide industrial application during the last 15 years. The rating of individual units increased from 50-kW active power output to 3000 kW, and larger units are contemplated. This paper deals with problems that are of primary importance for larger units only. The design procedures improved during the last years due to increased knowledge of the aftersaturation reactance of core-coil assemblies and due to new information available for core losses at high and distorted flux densities. The stability limits of filtered frequency changers are discussed and some new applications are mentioned.

Calculation of nonlinear eddy-current problems by the harmonic balance finite element method

The harmonic balance finite element method proposed solves the nonlinear time-periodic solution expressed as the sum of fundamental and harmonic components. A procedure for calculation which emphasizes the field computation in the harmonic domain is described. As a result, a reduction of the memory and calculation time is achieved. >

Low-frequency eddy-current loss estimation in long conductors by using the moment of inertia of cross sections

A simple method is presented to estimate low-frequency eddy-current losses in long nonmagnetic conductors of uniform cross section when subjected to axial or transverse magnetic field. The method involves calculation of the moment of inertia of the conductor cross section. In the case of transverse fields, the relationship obtained agrees with analytical results for cross sections which have a symmetry axis parallel to the incident field. For axial fields the proposed relationship agrees with the analytical expressions for circular and elliptical cross sections and gives results with reasonable accuracy for rectangular cross sections. >

Real-Time Measurement of Electric Arc-Furnace Disturbances and Parameter Variations

The general nature of electrical-supply network disturbances caused by arc-furnace operation is reviewed, including the guidelines adopted in several countries concerning disturbance-level estimation for single-and multifurnace installations. The meters available for the measurement of voltage flicker, including the international standard meter proposed by the International Union of Electroheat (UIE) are briefly described. The basic statistical properties of arc-furnace disturbances and parameter variations, treated as random variables, are discussed. Measured data are used to examine the probability distributions for variations in furnace voltage and current. Particular attention is given to methods of reliably measuring the disturbance and parameter-variation levels in real time on-line. Strategies are developed, and a microprocessor-based data-acquisition system, developed for this purpose, is described.

A Method of Examining in Detail Electric Arc Furnace Performance

A method of data acquisition and analysis is described that has been developed to assess in detail the performance of electric arc furnaces. The method has been implemented on a small single user minicomputer (a PDP 11/40) and on a large mainframe (an IBM 3033). The method was specifically developed in order to determine reliable statistical parameters that can be used to characterize arc furnace performance. The method is outlined, and its use is illustrated using data recorded on magnetic tape at the new Iron and Steel Company of Trinidad and Tobago (ISCOTT) plant. Results are presented that illustrate the operation of the ISCOTT furnace for scrap and pellet feed.

BIE formulation for skin and proximity effect problems of parallel conductors

The boundary integral equation (BIE) is used to determine the current distribution in the cross sections of a group of parallel conductors. Magnetic vector potentials at conductor surfaces are calculated by using the boundary element technique. The known current in each conductor is used as a constraint in the formulation. A source component (AA/sup s/) is introduced for the magnetic vector potential in order to maintain the balance between unknowns and equations and to transform Helmholtzs equation into a homogeneous equation. The choice of A/sup s/ is preferred over any other choice because it has physical meaning and its simplifies the calculation of various quantities such as voltage drop along the conductor, power loss, and line impedance. >

Determination of Harmonics of Converter Current and/or Voltage Waveforms (New Method for Fourier Coefficient Calculations), Part II: Fourier Coefficients of Nonhomogeneous Functions

A new method of determining Fourier coefficients is described. The advantage of the method is the substitution of algebraic addition to replace the integration operation in Fourier analysis. The method is applicable to every periodic function that satisfies Dirichlet conditions. Several waveforms of converter voltages and currents are analyzed as examples for the method.

Steady-state analysis and stability of a magnetic frequency tripler

A magnetic frequency tripler is a nonlinear device that is used to produce third-harmonic frequency output from a three-phase fundamental frequency source. Previous analyses of triplers assumed that the undesired harmonic currents generated by the magnetic cores could be returned to the input lines. In order to improve the performance of a frequency tripler, input-line filters are required. The presence of line filters influences profoundly the behavior of the device since harmonic voltage components other than the fundamental are allowed to exist at the frequency tripler terminals. In this paper a method is presented to analyze a line-filtered magnetic frequency tripler, and to investigate its stability.