Short-circuited Ring Research Articles

Analysis of interturn short circuit in regulating winding of power transformer based on field-circuit coupling

The interturn short circuit fault is one of the common faults in power transformers. At present, research on interturn short circuit faults focuses on high, medium, and low voltage windings, while there is relatively little research on interturn short circuit in regulating windings. Specifically, there is a lack of reported studies on the transient electromagnetic processes, magnetic field distribution, and electromagnetic force characteristics of interturn short circuits in regulating windings unconnected to the circuit. This study presents an actual fault scenario involving interturn short circuits occurring in the untapped portion of the regulating windings of a specific power transformer. A field-circuit coupled model was established to analyze the transient electromagnetic processes during the fault, and the model’s effectiveness was validated by comparing its results with actual fault recording data. Additionally, the magnetic field distribution and electromagnetic force characteristics during the fault were analyzed, and discussions were carried out regarding various ratios of short-circuit turns in the regulating windings. The results indicate that even when an interturn short circuit occurs in the portion of the regulating winding that is not connected to the circuit, the current in the short-circuited turns can reach several tens of times the rated value. Additionally, the leakage magnetic field and the electromagnetic force experienced by the short-circuited ring also increase significantly. The short-circuit ratio has a significant impact on the current of the short-circuited ring, leakage magnetic field intensity, and electromagnetic force. This study contributes to a better understanding of the impact of interturn short-circuit faults in the untapped portion of the regulating windings, offering crucial technical support for fault diagnosis and prevention of power transformers.

Экспериментальное исследование нелинейной эффективной площади рассеяния объектов в видеоимпульсном режиме

Quantitative information on the nonlinear scattering properties of probed objects at the impacts with signals close to baseband is presented, that will allow to make the requirements on transmitters and receivers of nonlinear baseband pulse radars. A prototype of a nonlinear baseband pulse radar using laboratory instruments has been developed. In the aperture of the antenna, it creates a pulsed field with an intensity of 35 W/m2 and at a front duration of 0,23 ns. The rings with a diameter of 6 сm made of copper wire with a cross section of 4 mm2 are used as sounding objects (a short-circuited ring as a linear object and a ring with the HSMS-8101 diode in its gap as a nonlinear object). The nonlinear radar cross section (NRCS) of a nonlinear object was 0,041 mm2, that fits into the typical range of NRCS for objects in a conventional (harmonic) nonlinear sounding.

Single-Layer, Dual-Port, and Dual-Mode Antenna With High Isolation for WBAN Communications

In this letter, a single-layer, dual-port, and dual-mode antenna with high isolation between the ports is suggested. This antenna consists of a short-circuited ring patch antenna that surrounds a substrate integrated waveguide (SIW)-based circular cavity in the center. An annular-ring slot is etched on the upper surface of the circular cavity and constitutes a cavity-backed annular ring slot antenna. Dimensions of the antenna are chosen in a way that TM₂₁ mode and TM₁₁ mode are placed at the frequency of 5.8 GHz for the short-circuited ring patch antenna and SIW cavity-backed antenna, respectively; the former has an omnidirectional radiation pattern and the latter has a broadside radiation pattern. Due to having two rows of vias, one for the short-circuited ring patch antenna and the other for SIW cavity-backed antenna, the isolation between the two ports is excellent owing to reduced surface waves. The measurement results of a fabricated prototype are properly consistent with the simulation results. This antenna is an appropriate option to be used in wireless body area networks for having simple structure, dual-mode, single-frequency, and high isolation.

Compact Dual-Band HTS Bandpass Filter Using Coplanar Waveguide Short-Circuited Stub-Loaded Ring Resonator

A compact coplanar waveguide (CPW) dual-band high-temperature superconducting (HTS) bandpass filter using a short-circuited stub-loaded ring resonator (SC-SLRR) is introduced in this paper. The equivalent circuit of the SC-SLRR is built and its resonant formulas are presented. The relationship between the parameters of electrical length and resonant performances are deduced. Resonant modes of the proposed resonators can be simultaneously excited and easily tuned for a dual-band application. To verify this methodology, a second-order CPW HTS dual-band bandpass filter operating at 2.36/4.93 GHz is designed. This filter is implemented on a 0.5-mm thick MgO wafer with a one-sided YBa 2 Cu 3 O 7 film, and it has the compact size of 0.146λg × 0.083λg. Measured results agree well with the simulated ones, which show that the minimum insertion losses of both bands are less than 0.15 dB.

Study on the Influence of Inter Turn Short Circuit Fault on Permanent Magnet Synchronous Motor Output Performance

When the inter turn short circuit (ITSC) fault occurs, the value of the short circuit ring loop current is large. A pulsating magnetic field generated by the loop current has a great influence on the motor inside magnetic field. The motor internal magnetic field is obviously distorted, and the motor output performance is limited. In order to study the influence of the fault on the permanent magnet synchronous motor (PMSM) output performance, first, a PMSM fault model is established based on the FEM. The influence of the fault on the motor electromagnetic field is studied. The motor magnetic field is decoupled and the armature magnetic field harmonic content is obtained by using the Fourier decomposition theory. Second, by using the Maxwell energy method, the output torque, radial force density and electromagnetic force are analyzed. The influence mechanism of the ITSC fault on the torque ripple and the electromagnetic force is revealed. Finally, the prototype test platform is built to study the ITSC fault, and the simulation results are compared with the experimental data. The correctness of simulation research is verified. The conclusions obtained are of the great significance for the PMSM fault analysis.

Simulation on Transient Characteristics of Inter-Turn Short Circuit Fault of Dry-type Air-Core Reactor Based on ANSYS Maxwell

Transient characteristic analysis of inter-turn short circuit fault has been done which is paramount for detecting the earlier fault of dry-type air-core reactor. Dynamic physical process of inter-turn short circuit is theoretically analyzed for dry-type air-core reactor from normal running condition to inter-turn short circuit fault condition. Using ANSYS Maxwell, transient field circuit coupling calculation model is set up and the transient characteristic of inter-turn short circuit fault is simulated, which is also verified by experiments. The study shows that the short circuit ring causes a sudden change of magnetic field at the position of short circuit which can be detected by the detecting coils installed on the package of reactor. Inter-turn short circuit fault can be detected in the earlier fault period by the method proposed in this paper.

The influence of inter-turn short circuit fault considering loop current on the electromagnetic field of permanent magnet synchronous motor

PurposeThe impact of the loop current (LC) on the motor magnetic field in the analysis of the inter-turn short circuit (ITSC) fault is always ignored. This paper made a comparative study on the electromagnetic field of permanent magnet synchronous motors (PMSM). The purpose of this study is to explore the necessary of the LC existing in the fault analysis and the electromagnetic characteristics of the PMSM with the ITSC fault when taking into account the LC.Design/methodology/approachBased on the finite element method (FEM), the fault model was established, and the magnetic density of the fault condition was analyzed. The induced electromotive force (EMF) and the LC of the short circuit ring were studied. The three-phase induced EMF and the unbalance of the three-phase current under the fault condition were studied. Finally, a prototype test platform was built to obtain the data of the fault.FindingsThe influence of the fault on the magnetic density was obtained. The current phase lag when the ITSC fault occurs causes the magnetic enhancement of the armature reaction. The mechanism that LC hinders the flux change was revealed. The influence of the fault on the three-phase-induced EMF symmetry, the three-phase current balance and the loss was obtained.Originality/valueThe value of the LC in the short circuit ring and the influence of it on the motor electromagnetic field were obtained. On the basis of the electromagnetic field calculation model, the sensitivity of the LC to the magnetic density, induced EMF, current and loss were analyzed.

Analysis of End-Winding Thermal Effects in a Totally Enclosed Fan-Cooled Induction Motor With a Die Cast Copper Rotor

Thermal overload protection techniques commonly use a simplified 1st order thermal model, which does not provide accurate stator winding temperature prediction and causes frequent undesirable stoppage of the motor in the processes. This paper proposes a higher order lumped parameter thermal network model to accurately predict stator winding temperature. First, the comparison of the predicted stator winding temperature from a 1st order thermal model with a higher order thermal model is performed. Second, a comparison between the actual and the predicted stator winding temperature rise is verified for a 20 hp totally enclosed fan-cooled copper rotor induction motor that has no rotor fins on its short-circuit ring to enhance heat dissipation compared with an aluminum rotor induction motor.

Improved designs of disk induction motors of block-module type for extreme environments

The construction of new disk induction motors of block-module type, which are a part of motor-transformer units (MTUs), are considered. The induction motors are intended for operation in hermetic objects under extreme conditions: a gas, steam-to-gas, and liquid environment at high pressures (up to 150MPa) and temperature (up to +600°C). The primary winding of the transformer part of the unit is connected to a three-phase network, and the secondary z-phase bar winding is located in Z grooves of the magnetic conductor of a transformer closed on one side by a short-circuited ring. The motor part of the unit contains an induction motor with a short-circuited rotor and stator with bar uninsulated winding connected to the transformer secondary winding; on the opposite side, it is closed by a short-circuited ring. The induction motor can be implemented with a disk short-circuited rotor located between two disk stators with bar windings. The bars of the transformer secondary winding are connected with Z bar-shaped hermetic lead-ins installed in a hermetic partition. Each bar-shaped hermetic lead-in is connected at the other end with n bars of the stator winding through intermediate conductive arc-shaped segments adjoining the stator. The operating principle and operation features of new disk induction motors of block-module type are considered.

Dual band and dual polarization short-circuited ring patch antenna

This paper presents a modification of the short-circuited ring patch antenna that operates in two bands: the lower band with linear polarization and the upper band with circular polarization. The new single-feed antenna has been manufactured and a comparison between measurements and numerical simulations is shown. Different characteristics such as radiation patterns, gain, and resonant frequencies have been analyzed. Moreover, a parametric study has been performed in both bands.

A Permanent Magnet Integrated Starter Generator for Electric Vehicle Onboard Range Extender Application

This paper deals with a permanent magnet (PM) brushless machine used for integrated starter generator (ISG) in an electric vehicle (EV) onboard range extender (ORX). Proper machine configuration selection is briefly introduced. Then, ISGs with both surface-mounted PM (SPM) and interior PM (IPM) rotors have been developed for comparatively analysis. Some techniques for eddy current loss reduction are discussed, while influence of the rotor protecting sleeve material and thickness, axial segmental sleeves, and short circuit rings (ShCRs) around each magnet are particularly investigated. Subsequently, experimental results as of the starter and generator are presented respectively. Moreover, cost evaluation is also presented.

Compact dual-band axially corrugated profiled horn for prime-focus reflector antenna

This paper reports a new compact dual-band axially corrugated profiled horn feed (DBCPH) for prime-focus reflector antenna at C-band (uplink and downlink frequency bands with bandwidth ratio of 1.6). DBPCH consists of one sinusoid profiled section and two internal axial corrugations (internal short-circuited ring slots), for obtaining a multimode horn feed. Such a blended structure is optimized over the specified frequency bands (3.68–3.70 and 5.865–5.915 GHz) to achieve various performance objectives (such as compactness, return loss, polarization purity, etc.). Measured and predicted results show that DBCPH provides better return loss >18.6 dB, low cross-polarization (better than −32 dB), and adequate edge taper at ±48° (8.5–11.7 dB) along with compact size (1.3λ aperture diameter and 0.88λ length at lower frequency). The horn would be used as a feed element for front-fed prime-focus reflector for pencil beam spacecraft antenna application.

Dual-band microstrip patch antenna based on short-circuited ring and spiral resonators for implantable medical devices

Along this document, an innovative dual band microstrip patch antenna is proposed for implantable medical devices. Particularly, the covered bands are MICS (402–405 MHz) and ISM (2.4–2.48 GHz). The antenna has a multilayer configuration where the feeding line and the radiating elements are located at different levels. The radiating elements of the antenna are a split ring resonator (SRR) coupled to a Spiral. Both elements are short-circuited to the ground plane to achieve size reduction. In addition, the effects of human body geometry and dielectric properties on the characteristics of the proposed design are studied. Three models of the human body are investigated: one-layer, three-layer and a realistic human body based on the Voxel Man dataset. Finally, simulated results have been validated by measuring return losses of the antenna embedded in mimicking gels, radiation patterns (in anechoic chamber) and radiation efficiency (in reverberation chamber).

Compact Multimode Patch Antennas for MIMO Applications [Wireless Corner

This work presents the design of compact multimode patch antennas for application in medium-size MIMO terminals combining spatial and radiation-pattern diversity. This design was inspired by previous work, which proposed the use of patch antennas providing two services at two frequency bands that required different radiation patterns. These precedents are briefly reviewed, before extending the concept of the dual-pattern two-frequency case to one in which diversity is demanded at a single frequency. A design with three modes at a single frequency is also accomplished. Some prototypes have been manufactured and measured. An example of the advantages of using these multimode antennas in terms of spectral efficiency in MIMO systems is also included. The key aspect of this work is the use of short-circuited ring patch (SCRP) antennas.

Inverted Mode Patch Antenna for Dual-Band Communications

In this letter, a single-port patch antenna with dual-band operation is presented. In order to provide two types of services, different radiation patterns for each band are proposed. The original aspect of the proposed design is the inverted disposition of modes compared with the short-circuited ring patches, where the resonant frequency of the zeroth-order mode is below the frequency of the first order one. In addition, the antenna is flexible for any application, because both frequencies are independent of each other.

The Effect of Sectioning on Superconducting Fault Current Limiter Operation

Various types of fault currents limiters have been proposed to reduce the fault currents in power transmission lines. The transformer type superconducting (SC) fault current limiter is one of them and has many advantages such as design flexibility. In normal operation mode the impedance is that of short-circuit transformer and has its minimum value. In the event of a load to fault an increase of the primary winding current causing a subsequent current increasing in the secondary SC winding (ring) and its quenching to the normal state. In this case the impedance turns to one in a no-load operation mode, i.e. is maximal performing the fault current limitation in the circuit to be protected. There has been investigated an effect of this sectioning of short-circuit SC windings or rings on the operation. A configuration of the transformer with symmetrical alternatively positioned disc windings is shown to be the optimal.

Analysis of a short-circuit ring impact problem and design of a new ventilator for a 625 kVA generator, using SVL

The necessity of an energy supplier was to solve an impact problem presented at the damper winding ring or short-circuit ring of a 625 kVA generator and to redesign a fan for it. The principal rest...

Analysis of a short-circuit ring impact problem and design of a new ventilator for a 625 kVA generator, using SVL

The necessity of an energy supplier was to solve an impact problem presented at the damper winding ring or short-circuit ring of a 625 kVA generator and to redesign a fan for it. The principal restriction was the time. It should be done in 15 calendar days, working with drawings of the machine, operational data and from specifications, taking measures from the real machine during just one day while the machine's maintenance began in order to solve the impact problem which real cause was not found yet. The answer was found working with the concept of simplified virtual laboratory (SVL) using finite elements analysis (FEA) and failure analysis from visual inspection. A fast and effective method which combines simplified 2D computational fluid dynamics (CFD) Models and analytical formulation from electrical machines bibliography allowing time and money saving is shown.

An analysis of inter-bar currents on a polyphase cage induction motor

This work uses a methodology based on 2D-Finite Element Method (FEM) and on the Circuits Theory (Independent Currents Method) to analyze the inter-bar currents on the rotor of cage induction motors. The Multi-Slice Technique is used to consider the skewing effect. Three conditions are considered: one inter-bar resistance, two inter-bar resistances and three inter-bar resistances. The results show the distribution of currents in the rotor bars, short-circuit rings and transversal resistances at a given time. The fundamental component of the inter-bar and surrounding bar currents are shown to help understanding the phenomenon.

Modeling of planar applicators for microwave thermotherapy

In order to improve the external applicators used for microwave thermotherapy controlled by microwave radiometry in medical applications, we propose specific planar applicators developed for heating: either annular ones to be used at the frequency equal to 915 MHz or in the shape of a horseshoe (short-circuited ring) for 434 MHz. The final goal of this paper is the realization of a honeycomb network for the treatment of larger areas and greater volumes.