Coupled Circuit Theory Research Articles

Study on Electromagnetic–Dynamic Coupled Modeling Method—Detection by Stator Current of the Induction Motors with Bearing Faults

Detecting motor bearing faults by stator currents is of great importance as it improves the adaptability of measurement means to different environments and reduces the number of sensors. Therefore, many studies have been conducted to investigate bearing faults by constructing motor models, most of which have used signal models to simulate the dynamics of the bearings. However, the signal model may be exposed to the issue that the nonlinearities in the bearing operation are neglected, thus oversimplifying the coupling effects between the electromagnetic and dynamics models. Hence, a coupled electromagnetic–dynamic modeling method for induction motors based on multiple coupled circuit theory and the rotor-bearing dynamics model is proposed in this study to implement the coupled simulation of electromagnetic and dynamic models. The air gap length and rotor velocity are used as coupled parameters for the calculation of stator–rotor mutual inductance and ball contact deformation, respectively. The simulation results show that the proposed model can effectively implement the electromagnetic–dynamic coupled and reflect the bearing fault characteristics in the current signal. Experiments were conducted on induction motors with typical winding configurations under laboratory conditions. The comparison results verify the effectiveness of the proposed modeling method.

An analytical model for squirrel cage induction machine with broken rotor bars derived based on the multiple coupled circuit theory and the winding function approach

SummaryIn this paper, a squirrel cage induction machine (SCIM) with broken rotor bars is modeled by using the multiple coupled circuit theory and the winding function approach. This analytical model includes all the spatial harmonic components of air gap magnetomotive force and is applicable to the study of transient machine behaviors. Equivalent circuits that are consistent with the topologies of healthy and faulty cage rotors are developed. The equivalent circuit for the healthy rotor of a SCIM having an integer number of rotor bars per pole is simplified further by exploiting the symmetry of the winding functions of the stator. In the equivalent circuit for a healthy rotor, inserting an independent current source in the bar that breaks in the damaged rotor, whose current is the negative of the current through the same bar, and replacing all the voltage sources in the rest of the bars with short circuits result in an equivalent circuit that can be employed to solve for the deviations in rotor mesh currents caused by bar breakage. A simulation is carried out in MATLAB/Simulink for a 2.2 kW, three‐phase, four‐pole SCIM with 28 rotor bars and a laboratory test rig is built. The effectiveness of the proposed model was validated by the good agreement of the simulation results with the experimental data.

Mathematical Modeling, Simulation and Experimental Testing of Interior-Mount LSPMSM Under Stator Inter-Turn Fault

Accurate modeling is the first step in developing a model-based diagnostics tool for different types of failures in electric motors. In this paper, a mathematical model for an interior-mount line start permanent magnet synchronous motor (LSPMSM) under the stator inter-turn fault is developed based on the principles of magnetic coupled circuit theory, electromechanical energy conversion and reference frame theory. The developed mathematical model is simulated using MATLAB and experimentally validated using a 1-hp, 4-pole, 400-V LSPMSM. To investigate the performance of the motor under the stator inter-turn fault at different loading levels, experimental and simulation results are compared and analyzed for both transient and steady-state responses of the current and speed. The simulation and experimental results are in very good agreement and show that under the stator inter-turn fault, the current magnitude and time response of the phase that contains the inter-turn are highly affected. In addition, due to asymmetry in the stator windings under this fault, the speed experiences some oscillations at steady state. Hence, the developed model can be used to detect the possibility and location of the stator inter-turn fault in an LSPMSM.

Study of Power Flow in an IPT System Based on Poynting Vector Analysis

This paper analyzes the power distribution and flow of an inductive power transfer (IPT) system with two coupled coils by using the Poynting vector. The system is modelled with a current source flowing through the primary coil, and a uniformly loaded secondary first, then the Poynting vector at an arbitrary point is analyzed by calculating the magnetic and electric fields between and around of the two coils. Both analytical analysis and numerical analysis have been undertaken to show the power distribution, and it has found that power distributes as a donut shape in three-dimensional (3D) space and concentrates along the edges in the proposed two-coil setup, instead of locating coaxially along the center path. Furthermore, power flow across the mid-plane between the two coils is analyzed analytically by the surface integral of the Poynting vector, which is compared with the input power from the primary and the output power to the secondary coil via coupled circuit theory. It has shown that for a lossless IPT system, the power transferred across the mid-plane is equal to the input and output power, which validates the Poynting vector approach. The proposed Poynting vector method provides an effective way to analyze the power distribution in the medium between two coupled coils, which cannot be achieved by traditional lumped circuit theories.

New approach for the modeling of induction machines operating under unbalanced power system

Summary In this paper, a new analytical method for the modeling of the star connected induction motors operating under unbalanced power supply is developed using coupled circuits theory. This method takes into account the increase of the common point voltage during unbalanced supply conditions. The equations, which describe the state model as well as the calculation of machine inductances, are presented. The calculation of inductances is based on the magnetomotive force distribution through the machine air-gap. The advantages of the proposed method are multiple. The space and time harmonics can be taken into account. It can also be extended for the analysis of faulty induction machines. Magnetic saturation, skin effect, skewed rotor, and slotting effects can be integrated in the calculation of the machine inductances by introducing some techniques to the basic coupled circuit theory. This method reduces strongly the time simulation because of the simple numerical representation of the inductances and their derivatives. The obtained results show good agreement with other results, which have been obtained using finite elements method and symmetrical components approach. The particularity of this work is that it takes in consideration the increase of the common point voltage during unbalanced supply conditions. Simulation results show the consistency and the applicability of the proposed method for the modeling of induction motors operating under unbalanced power system. Copyright © 2016 John Wiley & Sons, Ltd.

REDUCTION OF LEAKAGE MAGNETIC FIELD IN ELECTROMAGNETIC SYSTEMS BASED ON ACTIVE SHIELDING CONCEPT VERIFIED BY EIGENVALUE ANALYSIS

Leakage flelds are one of the main issues in design of electromagnetic systems. Some of these flelds close their paths through the core and air, giving rise to non-ideal behavior of the magnetic systems. This paper explains a novel concept of active shielding which consists of two compensation coils in series and generates a counter fleld opposite to the leakage flelds leaking from an iron-core system. As the method is based on physical reasoning of electromagnetic coupled circuit theory, the design criterions for the compensating coils parameters, their number of turns and their adaptation to the systems, were considered. The state of the art is presented by a model which is verifled by roots of system characteristic equations, using state equations. In a case study, this method was investigated in a 25kA (125kVA) current injection transformer (CIT) system delivering a secondary current as closely proportioned to the primary current as possible, using flnite element method (FEM) simulation. This paper will also push the state of the art by reducing the age efiect of the CIT through mechanical force reduction.

結合回路理論による渦電流形センサの解析

結合回路理論による渦電流形センサの解析

Current distribution in the LN 2 cryocable

This paper reveals the currently preferred design of conductors and eddy-current shield for the proposed liquid nitrogen cooled, vacuum insulated, underground transmission line. The conductors are sector-shaped tubes containing the coolant. The eddy-current shield, placed outside the thermal insulation, is also the vacuum pipe. Coupled circuit theory and Neumann's formula for the mutual inductance between metal filaments have been used to compute the current distribution. It was found to be strongly distorted by the skin effect and a little asymmetrical due to the proximity of the other two phase conductors. Over the operating temperature range, the a c-d c conductor loss ratio varies from 2·5 to 4·0. All steady torque which tends to rotate the conductor assembly inside the shield. Each conductor is subject to a rather strong lateral pulsating force.

Electromagnetic Forces on a Metal Disk in an Alternating Magnetic Field

Many fast-acting electromechanical devices utilize the repulsion forces produced on a metal disk subjected to a transient magnetic field. Coupled circuit theory yields a simple expression for this force in terms of an equivalent inductance. The equivalent inductance, however, is difficult to evaluate by theoretical and/or experimental methods when the metal disk is very close to the magnet coil. A numerical method for calculating the electromagnetic forces in such devices is described.

Parametric up-converter frequency response from coupled circuit theory

Application of the theory of transformer-coupled circuits to parametric up-converters indicates that a double-peaked gain response may be obtained with an upper-sideband converter having single-tuned input and output circuits.

Coupled Circuit Theory of Schrage Motor and Kron's Generalized Theory of Machines

Coupled Circuit Theory of Schrage Motor and Kron's Generalized Theory of Machines

Equivalent Circuits for Two-Dimensional Magnetic Fields: II - The Sinusoidally Time-Varying Field

PART I [1] of this series established a simple resistive analog to represent the static magnetic field. It was shown that by the use of a dc constant current network the magnetic vector potential solution of static field problems could be obtained including the correct boundary and internal field relations. Mention was made of the contribution of Roberts [2] in regard to the use of the RC analog to simulate a solution of Maxwell's equation for 2-dimensional time-varying fields. An extension of the analogy shows a revealing relationship of the RC network to the usual coupled circuit theory. It is the purpose of this paper to discuss the relationship and the application of the RC analog to the area of coupled circuit phenomena, relying primarily on circuit concepts familiar to electrical engineers.

Alternating and Transient Conduction Currents in Straight Conductors of any Cross-section†

ABSTRACT Hitherto the only method available for analysing current flow in conductors of large cross section for the transmission of electrical power has been that of quasi-stationary field theory, ns first developed by liayleigh. It provides rigorous solutions for conductors that are circular, straight and of great length. The problem has been re-examined with coupled circuit theory which was originally devised for the design of electromagnetic tests. Et proves to be suitable for the quantitative and qualitative study of finite length conductors of any cross-sectional shape. There is every prospect that it can be extended to non-straight conductors. Taking a rectangular busbar as an example, it is shown how numerical solutions of current distribution, energy dissipation and storage, conductance and susceptance may be obtained with the aid of computers. Also demonstrated is the use of normalized inductance coefficients for predicting the effect of changes in conductivity and size from measurements on a sin...

An Examination of the Coupled-circuit Theory of Eddy-currentsf

ABSTRACT The use of eddy-currents in non-destructive testing has been hampered by the lack of tractable theoretical models. Several recent works have attempted to remedy this by treating the conducting body as an assembly of elemental line circuits and thon applying coupled circuit theory. It is shown that certain assumptions made in the application are in error, thereby severely restricting the generality of the results.

Steady-state Electrodynamics of a Cylindrical Body in Axial Motion†

Coupled circuit theory (GCT) has been applied to an electromagnetic system in which a cylindrical conductor moves axially through a filament carrying a forced energizing current. With both this current and the relative velocity being arbitrary functions of time, it results in infinite series expressions for the current induced at any point in the cylinder, the e.m.f. induced in an open-circuited, external, sensing filament, the mechanical reaction force between cylinder and energizing filament and the rate of energy exchange, The general equations have been further developed for the three specific cases of (i) direct current excitation and constant relative velocity, (ii) direct current excitation and accelerated relative motion and (iii) alternating current excitation and constant relative velocity. It has also been shown how to study the effects of varying size and conductivity by employing scaled inductance coefficients. It is argued that the application of Lorentz transformations to the Maxwell-Hertz ...

Relations between the Parameters of Coupled-Circuit Theory and Transducer Theory with Some Applications

Relations between the impedance parameters usually used in coupled-circuit theory and those of transducer theory are derived. These indicate some useful methods of attacking certain problems-the determination of resonance conditions in a chain of coupled circuits, for example.

Theory of Coupled Circuits, under the Action of an Impressed Electromotive Force, with Applications to Radiotelegraphy

Theory of Coupled Circuits, under the Action of an Impressed Electromotive Force, with Applications to Radiotelegraphy