Coupling Circuit Research Articles

Investigation of magnetic resonance coupling circuit topologies for wireless power transmission

AbstractMagnetic resonance coupling circuits have four general topologies; however, there is a lack of comprehensive theoretical analysis with experimental verification for each of these topologies regarding their attractiveness for wireless power transfer (WPT). This article provides this for each of the four topologies to fully understand their differences and allow the selection of the most appropriate type based on system requirements. In addition, a problem associated with the resonance coupling method is the phenomenon of frequency splitting, which can lead to a high‐power transfer efficiency but low‐load power at the resonant frequency. Reasons for frequency splitting and methods of circumventing the problem will be illustrated in this article. Of the four topologies, the series‐parallel (SP) (input‐output) circuit configuration is the most efficient for the realization of a WPT system with a large load impedance, in terms of achieving both a high power transfer efficiency and high‐load power.

Analyzing Temperature Rise and Fluid Flow of High-Power-Density and High-Voltage Induction Motor in the Starting Process

Transient characteristics in the starting process play an important role in the design and operation of high-power-density and high-voltage induction motor. A field–circuit coupling model is proposed to analyze the transient fluid flow and temperature rise of a YJKK 500-4 2500 kW HPDHV induction motor in the starting process. The wind resistance network model is built to investigate the transient fluid flow and is used to obtain the heat dissipation boundary condition of the transient temperature calculation. The transient electric current is the key to the heat source of the temperature distribution and is calculated by the dynamic mathematical model. According to the obtained heat dissipation boundary condition and heat source, the 3-D fluid–solid coupling model is solved to obtain the transient temperature distribution. Moreover, the highest temperature rise in the starting process is greatly affected by the load. The simulation results show that the smaller fluid flow and the starting current make the winding temperature rise rapidly before the rotating speed of the motor reaches the rated value. When the load is much heavier, the starting time becomes longer and the winding temperature in the starting process will rise rapidly. The experimental results indicate that the proposed model is validated.

A Modified Direct-Quadrature Axis Model for Characterization of Air-gap Mixed Eccentricity Faults in Three-Phase Induction Motor

Advanced signal processing techniques and high-speed analog to digital converters enabled on-line detection of internal faults of induction motor even at inception. Reliable and accurate identification of fault signatures in practical situations is always a challenge due to load oscillations, supply harmonics or the presence of multiple faults. Hence model-based analyses are essential for diagnostic studies of faults in machines. This paper proposes a modified direct and quadrature (d-q) axis based approach for modeling a three-phase squirrel cage induction motor with air-gap mixed eccentricity faults. In the proposed model, air-gap length- and thus magnetizing reactance- are modeled as a rotor position-dependent function, to represent various variable air-gap fault conditions. Stator current spectrum is used as the diagnostic signal for detection of the presence of these faults. This simple approach of modeling is computationally less intensive compared to alternative approaches such as multiple coupled circuit modeling and finite element approach. Characteristic signatures of mixed eccentricity fault obtained by simulation studies were also validated in the motor current spectrum obtained through experimentation on a motor with prefabricated eccentricity.

Transmission characteristics of magnetic resonance coupling‐based multi‐load wireless power transmission system

If the magnetic resonance coupling-based wireless power transmission system has multiple receivers, cross-coupling will occur between the transmitter and the receiver, resulting in the variation of transmission characteristics when compared with the case of a single receiver. To solve this problem, a mutual inductance coupling circuit model for double-relay and multi-load transmission system and a calculation model for mutual inductance between solenoid coils in the same plane have been built to study the transmission characteristics of the system through simulation and testing. The study results show that: the cross-coupling effect between the transmitter and the receiver will cause resonance frequency shift, or even lead to the variation of resonance frequency splitting characteristic; when compared with a single-load system, the multi-load system may increase in total transmission power and efficiency; generally, with the introduction of additional receivers, the receiving power and efficiency of the original loads will decrease; along with the increase in circuit spacing and the decrease in cross-coupling, the transmission characteristics will gradually regress to the state of a single-load system. In this article, the calculation model for mutual inductance is correct and the maximum relative error in these calculating examples is 5.28%.

Analysis of Bridge Currents and UMP of an Induction Machine With Bridge Configured Winding Using Coupled Field and Circuit Modeling

Unbalanced magnetic pull (UMP) reduction is an important aspect of high-speed electrical machines and it can be reduced using a specialized winding scheme called bridge configured winding. A bridge configuration winding has two parallel paths in each phase. The mid points of these two parallel paths can be short-circuited to achieve passive control of the UMP or a power supply can be added in between these points to achieve active control of UMP. Moreover, it is important to understand the behavior of UMP in different eccentricity conditions for its active suppression. A finite-element modeling of a bridge configured induction machine has been developed to study the effects of different eccentricity conditions on UMP and bridge currents. A generalized circuit equation has been coupled with the field equation for the implementation of bridge configuration winding. All of the three kinds of eccentricity conditions have been simulated. In addition, two experimental setups have been developed to study the UMP-induced vibration and to study the effect of eccentricity on bridge currents.

Dynamic simulation of induced voltages in high voltage cable sheaths: Steady state approach

This paper presents a novel approach to the modeling of high voltage underground cables. Its main contribution is that it considers induced effects. Indeed, it incorporates the estimate of induced voltages and currents in cable sheaths in steady state due to the nearby cables and sheaths, for different types of sheaths connections and for various single-phase short-circuit configurations and three-phase short-circuits. Furthermore, it allows multiple circuits to be coupled automatically in a simple way. An intuitive and friendly simulation tool has been implemented that allows the automatic generation of multiple coupling circuits and to calculate all these induced effects caused by the connection of the sheaths and the distance between cables. It has been validated by comparing it with the expected theoretical data and to other simulators with satisfactory results.

Real-Time Finite-Element Simulation of Electromagnetic Transients of Transformer on FPGA

The computation of the electromagnetic transients in a power transformer with nonlinear material using the finite element method (FEM) is so dense that the traditional nonlinear solver employing the Newton–Raphson method can hardly execute in real time. In this paper, we emulate the finite-element computation of electromagnetic transients of a transformer in real time for the first time. The transmission line modeling (TLM) method employed in the FEM successfully decoupled the nonlinear elements from the linear network so the nonlinearities could be solved individually, which is perfect for parallel processing. The parallelism of the TLM-FE solution is sufficiently explored and realized on a field-programmable gate array with deep data pipelining, and the implementation can execute in real time and provide detailed field information of the transformer during the transients. The proposed noniterative field–circuit coupling enabled the transformer to interface with an external network and the comparison with commercial FEM software proved the accuracy and computational efficiency of the real-time FE model.

A Low-Loss Design of Bandpass Filter at the Terahertz Band

This letter demonstrates a terahertz (THz) bandpass filter with a center frequency of ~340 GHz, low insertion loss of ~ -0.6 dB, and bandwidth of ~5.3%. The diaphragm thickness is quantitatively analyzed to obtain accurate filter parameters based on equivalent circuit and diaphragm coupling in THz band for the first time, and the simulation results based on calculated filter parameters show that diaphragm thickness has great influence on the filter performance. The test results show a good agreement with the theoretical analysis and simulation results. Meanwhile, the relationship between fabrication error and insertion loss was discussed and a quantitative mathematical model is given. The filter also shows an excellent performance when compared with the performance of other filters from the current literature reports.

Analytic Model for Induction Motors Under Localized Bearing Faults

The bearing faults are the major root cause for the induction motor failures; however, almost all the related fault diagnosis methods have been based on the laboratory tests, which are costly and inflexible. Localized defects in various components of roller bearings cause radial vibration of the rotor, little variation of the load torque, and various harmonics in the stator current. Ignoring the load torque variation, this paper applies the multiple coupled circuit modeling to simulate three-phase squirrel-cage induction motors under the localized bearing faults by introducing appropriate air gap function. Fast Fourier transform is used for exact analysis of the harmonic content of the inverse of the air gap function. The analysis is completed by including the saturation effect and the inherent eccentricity of the motor. Then, a broad list of harmonics presentable in the stator current spectrum under the bearing faults is determined. The list may include the characteristic vibration frequencies related to the bearing components faults. Also, it is clear that the inner raceway fault can produce the same harmonics in the stator current as produced by the mixed eccentricity. Experimental results approve the simulation results and the mentioned facts.

Cascade Magnetic Cumulation Generator on the Basis of Inductively Coupled Circuits with A Variable Coupling Coefficient

A scheme of a multicascade magnetic cumulation generator based on a dynamic variation of the coupling coefficient of inductively coupled circuits is proposed. Each cascade contains two circuits including two pairs of inductively coupled coils. One pair of coils is subjected to simultaneous deformation, and one of the coils in the other pair is arranged with the opposite connection. It is shown that the energy in the load can be gradually increased (from one cascade to another) by using additional cascades. By an example of a two-cascade system, the proposed circuit is compared to the known circuits of the cascade system design based on the magnetic cumulation principle (generator with a step-up transformer and dynamic transformer). Within the framework of the model that ignores the ohmic resistance of conductors, it is demonstrated that the proposed scheme allows one to obtain a greater energy in the high-inductance load than the schemes with a step-up or dynamic transformer owing to a change in the sign of the magnetic flux in the secondary circuit. It is found that the increase in energy in the new scheme is independent of the coupling coefficient (at high values of this coefficient) and becomes greater as the number of cascades is increased.

Study of Response Difference Amplification and Bionic Coupled Circuit in Small Acoustic Array for Spatial Localization

Precisions of localization are a function of the size of an array. A kind of parasitoid fly, Ormia ochracea, performs an extraordinary directional hearing ability despite its tiny-scaled auditory organ. In this paper, vibration modes and transfer functions of the Ormia ochracea's ear model were calculated, and the phase difference amplification in responses are analyzed to investigate the directional hearing mechanism. A novel three-element bionic model is proposed for spatial sound source localization for small distance-wavelength ratios. The amplification of the phase difference of this model is verified. In order to realize the bionic localization model, based on electric-mechanic analogy method, a system that consists of a triangular acoustic array and a bionic coupling circuit is designed and tested. Frequency responses of the circuit output, as a means of transfer function of the system, are taken into estimation of the source directions. The result has shown that this circuit design has better performance in estimating the direction of sound sources compared to the uncoupled array with same size.

Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance (RL), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage (VOUT) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous VOUT amplification process.

Stabilization of Linear Multistage Amplifiers

In a given linear, multistage, cascaded amplifier [1] comprising passive coupling circuits and active two-ports alternatively, the problem is where in the amplifier the stabilizing circuit elements should be placed to eliminate instability, and of what type and value. Our investigations are based on a new recursive formula for the determinant of tridiagonal matrices. Relation of our results to the Stern stability factor has been obtained. A verification in numerical examples has also been provided.

Design of active power filter for narrow-band power line communications

In power line communication (PLC), couplers such as coupling transformers and band-pass matching coupling circuits are usually required for coupling, band-pass filtering, and impedance matching. However, the cost and size of transformers prevent them from being an economic and compact solution for PLC couplers. In addition, passive band-pass matching coupling circuits need accurate impedance matching and possibly incur power losses. In this paper, a 6th order multiple feedback (MFB) active power filter with the minimum number of components was designed for narrow-band PLC, which has high input impedance and low output impedance, allowing outstanding performance in main voltage isolation, suppressing the current-harmonics and compensating the reactive power simultaneously. Finally, simulations were conducted in the range of 95 kHz-125 kHz (CENELEC “B-band”), which confirmed that the new filter met the CENELEC requirements for transmission and disturbance levels.

Cascade Magnetocumulative Generator on the Basis of Inductively Coupled Circuits with a Variable Coupling Coefficient

Cascade Magnetocumulative Generator on the Basis of Inductively Coupled Circuits with a Variable Coupling Coefficient

Coupling and decoupling of the accelerating units for pulsed synchronous linear accelerator

A pulsed synchronous linear accelerator (PSLA), based on the solid-state pulse forming line, photoconductive semiconductor switch, and high gradient insulator technologies, is a novel linear accelerator. During the prototype PSLA commissioning, the energy gain of proton beams was found to be much lower than expected. In this paper, the degradation of the energy gain is explained by the circuit and cavity coupling effect of the accelerating units. The coupling effects of accelerating units are studied, and the circuit topologies of these two kinds of coupling effects are presented. Two methods utilizing inductance and membrane isolations, respectively, are proposed to reduce the circuit coupling effects. The effectiveness of the membrane isolation method is also supported by simulations. The decoupling efficiency of the metal drift tube is also researched. We carried out the experiments on circuit decoupling of the multiple accelerating cavity. The result shows that both circuit decoupling methods could increase the normalized voltage.

Damper Currents Simulation of Large Hydro-Generator Using the Combination of FEM and Coupled Circuits Models

A high-order model is required for an accurate simulation of the synchronous alternator spatial harmonic content. However, some hydro-generators have fractional slot per pole per phase windings, and carrying transient simulations of these machines with finite-element software often leads to unacceptable computation time. This paper details a large alternator modeling method that provides an excellent compromise between accuracy and speed. It is a combination of magnetostatic finite element method and coupled circuits model. The paper details the construction of this model and explains the procedures to identify several model parameters from experimental data as the standstill frequency response and open and short circuit tests. The effectiveness of this modeling method is validated by the study of a large 109-MVA hydrogenerator having an instrumented rotor pole. We compare transient and steady-state simulation waveforms of the damper bar currents during sudden two- and three-phase short-circuit to the experimental measures.

Harmonic suppression analysis of a harmonic filtering distribution transformer with integrated inductors based on field–circuit coupling simulation

This study analyses and evaluates the feasibility of a harmonic filtering distribution transformer (HFDT) for a harmonic reduction in low-voltage distribution networks. With this new-type transformer, power quality of the distribution systems can be improved by preventing the low-voltage-side harmonic currents from penetrating the higher voltage side. As the physical size of available space in prefabricated substations is strictly limited, necessary low space occupying filtering techniques are needed. Therefore, an HFDT with integrated filtering inductors (IFIs) capable of being implemented in regular air-insulated prefabricated substations is proposed. Two sets of passive filters configured by IFIs and external capacitors are employed for harmonic filtering. Two methods for estimating the inductance parameter are provided. One is the dimension-based method and the other is the reduced-order inductance matrix method. The relevant harmonic reduction analysis is based on simulations with a field–circuit coupling model, which consists of a three-dimensional finite-element electromagnetic model of an HFDT with IFIs and a corresponding electric circuit of a simplified distribution network. These simulations prove that the described HFDT can effectively reduce specific harmonic currents with IFI-based filters. Finally, the successful suppression of harmonics is demonstrated and discussed based on field-test measurements.

Symmetric stripline duplexer

The compact duplexer using the symmetric stripline and containing the fifth-order comb filters in transmit channel TX (2300–2370 MHz) and receive channel RX (2510–2580 MHz) is constructed, and the characteristics of obtained duplexer are measured. This duplexer is built using dielectric material Al2O3 (Alumina, polikor) with high thermal conductivity that makes it possible to use the operating power of 10 W at small dimensions 57´11.8´4 mm. The losses in bandpass of TX and RX filters did not exceed 3 dB during the filter attenuation at adjacent channel frequencies of no less than 60 dB. It is shown that the selection of the width of metallized strip at the base of quarter-wave resonators makes it possible to change the duplexer width for attaining the required value. The circuit of coupling of resonators with loads used in this design made it possible to obtain a sufficiently high level of isolation from each other for RX and TX channels of duplexer. This level does not exceed 60 dB. The finite thickness of internal conductors of stripline amounting to 16 mm is taken into account while building the duplexer that results in good agreement between the simulation and measurement results.

Study on frequency characteristics of wireless power transmission system based on magnetic coupling resonance

In order to study the frequency characteristics of the wireless energy transmission system based on the magnetic coupling resonance, a circuit model based on the magnetic coupling resonant wireless energy transmission system is established. The influence of the load on the frequency characteristics of the wireless power transmission system is analysed. The circuit coupling theory is used to derive the minimum load required to suppress frequency splitting. Simulation and experimental results verify that when the load size is lower than a certain value, the system will appear frequency splitting, increasing the load size can effectively suppress the frequency splitting phenomenon. The power regulation scheme of the wireless charging system based on magnetic coupling resonance is given. This study provides a theoretical basis for load selection and power regulation of wireless power transmission systems.