Winding Turns Research Articles

Research on Winding Dynamic Force and Displacement of Winding in Interturn Short Circuit of Stereo Roll Iron Core Transformer

Abstract The short circuit fault between the turns of the transformer winding accounts for 60% ∼ 70% of the whole winding fault, which seriously adversely impacts the regular functioning of the transformer. This study focuses on analysing the dynamic force and displacement characteristics of the winding in a stereo roll iron core transformer when an inter-turn short circuit occurs. First, a stereo roll iron core transformer finite element model in three dimensions is created. The electromagnetic-solid mechanics coupling method is used to figure out and study the transformer winding’s inter-turn short-circuiting current, leaking electromagnetic field, dynamic force, and displacement distributions. Furthermore, an experimental platform is built to simulate the inter-turn short-circuiting of a stereo roll iron core transformer. The displacement in the time domain and the acceleration in the frequency domain of the winding during the short circuit that occurs between turns will be recorded and analyzed. Finally, it is concluded that under normal working conditions, the winding vibration frequency is between 100 ∼ and 500 Hz. After 19 turns of the short circuit, the winding displacement increases by 32% ∼ 60%, and the high-order harmonic content of the winding vibration frequency increases significantly.

High Step-Up Dual-Switch X-Source DC–DC Converters Integrating Various Capacitor-Winding-Diode Voltage-Double Technology

In this paper, a new class of high step-up dual-switch X-source DC-DC converters integrating various capacitor-winding-diode voltage-double technology are presented, which called respectively parallel-winding dual-switch X-source (PWDS-XS) DC-DC converter, series-winding dual-switch X-source (SWDS-XS) DC-DC converter, and flipped parallel-winding dual-switch X-source (FPWDS-XS) DC-DC converter. According to different winding homonymous end connections, voltage gains and turn ratios of proposed converters exist two relations: inversely proportional relations and positive proportional relations. Also, all proposed topologies can produce the higher voltage gain, and own the lower voltage stresses. Operation principles, math derivations and performance advantages of the proposed converters are analyzed in detail. Finally, the experimental protype is built to demonstrate the operation feasibility of the proposed converter.

Optimization Design of DC Electromagnet Coil Considering the Power Consumption and Cost

Electromagnet coil is mainly composed of enameled wire which wound on the coil skeleton, and the function is to convert the electrical signal into a magnetic signal, which is a very important electric‐magnetic conversion element. When designing the electromagnet coil, usually only the total winding turns and winding inner diameter can be calculated, and the specific design parameters such as the diameter of copper wire, paint layer thickness, and winding turns of each layer can only be selected through experience, indicating that the design method should be improved. In addition, the unreasonable design parameters will seriously affect the power consumption and cost of coil, so it is highly necessary to improve the optimization design method. In order to solve the above problems, an optimization design method for DC electromagnet coil is proposed in this paper. This method simultaneously takes into account both power consumption and manufacturing cost, and can achieve the optimal matching of design parameters. In this paper, the structure of electromagnet coil is introduced, and the theoretical calculation model of resistance is improved first. Then, according to the expected requirements of electromagnet coil for steady current, the optimization design method is proposed and the optimal design parameters are obtained. Finally, the effectiveness of the proposed optimization design method is verified by the test platform of electromagnet coil. The results show that the electromagnet coil designed by the optimization design method fully meets the expected requirements. The relevant research results can provide reference for the optimization design of electromagnet coil, which has a certain engineering practical value. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

High-sensitive state perception method for inverter-fed machine turn insulation based on FrFT-Mel

Amidst the swift advancement of new power systems and electric vehicles, inverter-fed machines have progressively materialized as a pivotal apparatus for efficient energy conversion. Stator winding turn insulation failure is the root cause of inverter-fed machine breakdown. The online monitoring of turn insulation health can detect potential safety risks promptly, but faces the challenge of weak characteristics of turn insulation degradation. This study proposes an innovative method to evaluate the turn insulation state of inverter-fed machines by utilizing the fractional Fourier transform with a Mel filter (FrFT-Mel). First, the sensitivity of the high-frequency (HF) switching oscillation current to variations in turn insulation was analyzed within the fractional domain. Subsequently, an improved Mel filter is introduced, and its structure and parameters are specifically designed based on the features intrinsic to the common-mode impedance resonance point of the electrical machine. Finally, an evaluation index was proposed for the turn insulation state of inverter-fed machines. Experimental results on a 3kW permanent magnet synchronous machine (PMSM) demonstrate that the proposed FrFT-Mel method significantly enhances the sensitivity of turn insulation state perception by approximately five times, compared to the traditional Fourier transform method.

Experimental study of a teeth flux sensor for detection, location and severity evaluation of induction machine stator faults

PurposeThis paper aims to investigate the efficacy of teeth flux sensors in detecting, locating and assessing the severity of short-circuit faults in the stator windings of induction machines.Design/methodology/approachThe experimental study involves inducing short-circuit winding turn variations on the induction machine’s stator and continuously measuring the RMS values across teeth flux sensors. Two crucial steps are taken for machine diagnosis: measurements under load operating conditions for fault detection and measurements under no-load conditions to determine fault location and severity.FindingsThe experimental results demonstrate that the proposed approach using teeth flux sensors is reliable and effective in detecting, locating and evaluating the severity of stator winding faults.Research limitations/implicationsWhile this study focuses on short-circuit faults, future research could explore other fault types and alternative sensor configurations to enhance the comprehensiveness of fault diagnosis.Practical implicationsThe methodology outlined in this paper holds the potential to significantly reduce maintenance time and costs for induction machines, leading to substantial savings for companies.Originality/valueThis research contributes to the field by presenting an innovative approach that uses teeth flux sensors for a comprehensive fault diagnosis in induction machines. The originality lies in the effectiveness of this approach in providing reliable fault detection, location and severity evaluation.

Investigation of the processes of origin and development of the eccentricity of the air gap of traction synchronous electric motors

The purpose of the work is to develop a method for diagnosing the processes of origin and development of the eccentricity of the air gap by analyzing the frequency composition of the current vector of the electric motor. The practical significance of this work lies in the possibility of using the developed method for the diagnosis of traction motors. The result of the study was the developed mathematical model of a synchronous electric motor with permanent magnets with shortcircuited turns of the phase winding, which allows to study the behavior of the engine when the air gap between the rotor and the stator changes. Keywords mathematical model, traction motor, permanent magnets, diagnostics, rotor, stator, harmonics, eccentricity

Improvement of the uniformity of the magnetic field inside a short solenoid by the end winding system

Improving the level of homogeneity of the magnetic field in the middle of the working volume of a short solenoid makes it possible to improve devices for demagnetizing technical objects and studying the magnetic properties of materials. One of the means of increasing the level of homogeneity of the magnetic field in the middle of the solenoid is to approximate the shape of its winding to the closed surface. The use of a system of a solenoid and two end axisymmetric current windings with a common current source is proposed as such a surface. A mathematical model of the scalar potential of the magnetic field of such a system was built using spherical harmonic analysis, and functional dependences of the current density on each surface were obtained for its first harmonic, which is the dipole component of the magnetic field. Formulas for calculating the number of turns in the end windings and the geometric parameters of their arrangement and the simulated total magnetic field inside the proposed system are obtained. A comparative analysis of the homogeneity of the magnetic field created by a separate solenoid and a solenoid with end windings, depending on the geometry of the system, was conducted. The use of end windings significantly improves the uniformity of the magnetic field near the ends, especially on the axis of the solenoid. Due to this, the efficiency of the end windings significantly depends on the solenoid elongation indicator and allows you to increase the working volume by 5-20%, depending on this indicator. The proposed system makes it possible to obtain a magnetic field with a maximum deviation of 5% from uniformity for a solenoid elongation index of 2. As the elongation increases, the efficiency of the end windings decreases and for systems with an elongation of 10 or more, their use becomes impractical. The results of the analysis testify to the effectiveness of using the proposed system in devices for demagnetizing technical products that differ in a small indicator of the elongation of the working solenoid - primarily devices that create a uniform magnetic field with an amplitude decreasing over time of 240 A/m and are used in particular to remove soft residual magnetization from elements of space vehicles

Diagnostics of inter-turn short circuits in phase stator windings of permanent magnet synchronous machines

BACKGROUND: Currently, electric buses are becoming more widespread in the segment of urban passenger transportation due to the absence of harmful emissions and low noise levels. Permanent magnet synchronous machines (PMSM) are widely used as a traction motor.
 One of the most promising methods of monitoring the technical condition of traction motors is diagnostics using monitoring tools installed on board of a vehicle. The advantages of such methods include the possibility of regular frequent condition checks (as opposed to much rarer diagnostics in stationary maintenance points) and a more rapid response to the development of identified malfunctions, which significantly reduces the cost of maintenance and repair of expensive equipment. The disadvantages include limitations associated with a shortage of layout space for the placement of diagnostic equipment, with the limited capabilities of on-board computer facilities for the transmission and storage of diagnostic information and with the complexity of computational procedures of built-in expert diagnostic systems.
 Concerning the types of operational failures of PMSMs, which are the most common and the most severe in terms of the cost of restoring operability, these are inter-turn short circuits in the stator windings, increased eccentricity of the air gap between the stator and the rotor, bearing damage, as well as damage of the mechanical gearbox coupled with the electric motor.
 AIM: Identification the diagnostic signs of inter-turn short circuits in the phase windings of a permanent magnet synchronous machine, helping to detect these malfunctions on board of route urban vehicles at an early stage.
 METHODS: A mathematical model of a permanent magnet synchronous machine with short-circuited turns of the phase winding, which makes it possible to study the behavior of the motor with a various number of short-circuited turns, has been developed.
 RESULTS: For the first time, the requirements for diagnostic features for the on-board diagnostic system of an urban electric bus, making it possible to detect inter-turn short circuits in the phase windings of traction electric motors at the early stages of the origin of a malfunction, are formulated.
 The main parameters of the process of digital registration of phase currents have been obtained, helping to do measurements and to transmit signals through the onboard information network of the electric bus.
 Using simulation modeling methods, it was found that the peak values of the linear spectrum of the total current vector are stable diagnostic signs that make it possible to detect inter-turn short circuits in the phase windings of traction motors at the early stages of the origin of the malfunction.
 CONCLUSION: The practical value of the study lies in the opportunity of using the proposed methods for diagnosing the technical condition of traction electric drive units in urban passenger electric transport.

Short‐circuit current difference of parallel strands in winding turns and its influence on the distribution of electromagnetic force

AbstractTransformer winding turns often consist of multiple parallel strands. The spatial position variation of each strand affects the leakage inductance of each branch, resulting in an uneven distribution of short‐circuit currents within the winding turns. And this unevenness persists even when transposition structures are implemented. Traditional methods in transformer analysis frequently overlooked the distribution characteristics of short‐circuit currents when calculating electromagnetic forces. A frequency‐domain calculation method for analysing the current distribution in winding turns was proposed, with a deviation of less than 3% compared to existing analysis methods. Two typical 110 kV transformer models were utilised to investigate the influence of uneven current distribution on the spatial distribution of electromagnetic forces. The spatial distribution of short‐circuit electromagnetic forces in low‐voltage (LV) windings exhibited significant changes, with maximum change rates of 10% and 61.2% for axial and radial electromagnetic force, respectively, in a LV winding with 4 parallel strands. The research also analysed how strand radial width and axial height affect current distribution unevenness and proposed specific design principles to mitigate these disparities in winding design. The findings offer valuable insights for selecting structural parameters and assessing short‐circuit stability during transformer design.

Device fault diagnosis method based on digital twin server

The digital twin is a virtual replica of a physical system that can be used to simulate and analyze its behavior. In fault diagnosis, digital twin technology is used to create a virtual model of an industrial system, and simulate different scenarios to identify the causes of the fault, and predict the system behavior under different conditions. We propose an equipment fault diagnosis method based on digital twin server. Digital twin server is the intermediary between digital model and real device data interaction. Firstly, the principle and function of digital twin and digital twin server are introduced. Then the method of using digital twin server in equipment fault diagnosis is described. Finally, taking the fault diagnosis of underwater propeller as an example, the validity of the fault diagnosis method based on digital twin server is tested. The digital twin fault diagnosis system of underwater propeller connects the digital model and the real sensing equipment, realizes the fusion of virtual and reality, and the accuracy of the resolution of the short-circuit fault between turns of the stator winding of underwater propeller can reach 85%.

Transient-steady state vibration characteristics and influencing factors under no-load closing conditions of converter transformers

The converter transformer plays a key role in the HVDC transmission project. It will be put back into the power grid after a power outage for maintenance. The transient overvoltage and excitation inrush current during charging and closing will cause shock vibration and affect the stability of the internal mechanical structure. In addition, the on-load tap-changer (OLTC) shifting operation after closing will also lead to changes in the vibration characteristics. Because of insufficient research on vibration during closing transient and no-load operation, this paper measures the transient vibration change process during no-load closing and tap-changer action in a ± 800 kV converter station. Furthermore, the influence of voltage and winding turns changes on no-load vibration is also analyzed, and multi-characteristic parameters of vibration impulse factor, offset factor, and odd–even harmonic ratio are extracted to realize no-load state identification. The results show that the no-load vibration increases with the increase of the voltage, and decreases with the increase of the number of turns of the grid-side winding. More importantly, both the charging closing and the tap-changer action will produce vibration and shock components, and the maximum transient vibration exceeds 90 m/s2, which is 35.7 times that of the steady-state. Odd harmonic components of 50 Hz, such as 150 Hz, 250 Hz, etc., will appear in the vibration spectrum under the action of the 2nd, 4th, and other even harmonics in the excitation inrush current. While the non-excitation inrush current is mainly an even multiple of 50 Hz. The research results reveal the vibration characteristics of the converter transformer during closing transient and no-load operation, and provide a theoretical reference for the evaluation and identification of the converter transformer under all operating conditions.

Calculation of the depth of rope-tightening soft material and analysis of its relationship with the tightening force

To analyze the relationship between the tension force of a rope and the bundled material's indentation, a model of tightening by rope for soft material was designed for testing. By calculating the indentation depth of soft materials from rope stretching displacement, the variation law of the indentation depth of tightening soft materials with different mechanical properties of ropes was analyzed. As the stretching progresses, the more the rope winding turns, and the shallower the indentation depth. The friction coefficient between the soft material and the rope does not significantly affect the theoretical indentation depth. The theoretical indentation depth of high-strength ropes shows a linear variation pattern. The theoretical indentation depth of high-extension ropes is negative. With the theoretical indentation depth of the ordinary rope increasing first and then decreasing, its indentation depth curve shows a parabolic shape. Aromatic polyester rope, cotton chainette thread, and polypropylene rope were used to tighten ethylene-vinyl acetate (EVA) foam and test the indentation depth. The results show that the deformation of the rope is much lower than that of the EVA foam, and the depth of the strangulation is closely related to the tensile displacement and tightening tension. The measured value of the indentation depth is lower than the calculated value, and the greater the stiffness of the rope, the smaller the difference between the measured and calculated indentation depth. The indentation depth method was used to calculate the tightening effect of ropes with high rigidity and has excellent results.

Eddy Current and Loss of Graded-Resistance No-Insulation Coils in HTS Synchronous Machines of Electrical Aircraft

The No-insulation (NI) high temperature superconductor (HTS) machine is a promising propulsion technique for future large-scale electrical aircraft because of its high power density and enhanced thermal stability. However, in the machine environment, the ripple magnetic fields can induce significant eddy currents and losses on the NI coil. A grading turn-to-turn resistivity technique has been proposed to solve this problem, in which higher turn-to-turn resistivity is applied on the outermost turns of the NI coil, and lower turn-to-turn resistivity is kept on middle turns. The purpose of this research is to study the effects of grading turn-to-turn resistivity technique on the eddy current and loss of both single and multiple NI HTS coils exposed to ripple fields. To investigate the electromagnetic behavior and loss mechanism of NI HTS coils, a simulation model is proposed that couples the equivalent circuit model and finite element model. Results show that the grading turn-to-turn resistivity can effectively reduce the induced eddy current and lead to a uniform distribution of eddy current among turns of both single and multiple windings. It reduces magnetization loss in superconducting layers but increases the turn-to-turn loss on the radial contacts. These results are useful for the development of NI HTS machines with high thermal stability.

An E-Core Based Integrated Coupled Inductor for Interleaved Boost Converter

Interleaving in a boost converter is beneficial for lowering input and output current ripples through ripple cancellation due to phase-shift between channel currents. However, interleaving does not affect the channel current ripple. The channel current comprises circulating Differential Mode (DM) current and Common Mode (CM) boost current, whose ripples constitute the total channel current ripple. Inverse coupling between channel inductors effectively lowers channel current ripple while maintaining the same input and output current ripples. However, with a single inverse coupled inductor, its leakage inductance, which serves as a boost inductor, depends on the winding arrangement and is challenging to balance in both channels. To overcome this, the inverse coupled inductor can be implemented as a cascade of inverse (DM inductance) and direct (CM inductance) coupled inductors. The DM and CM currents and their ripples then depend on CM and DM inductances, respectively. Nonetheless, this approach results in increased size and count of magnetic cores. In this paper, an Integrated Magnetic Structure (IMS), based on a gapped EE-core, is proposed that combines both CM and DM inductances in a single core. The CM and DM inductances are independent and depend on separate winding turns. A reluctance model is derived, and a design procedure is developed where core parameters are expressed in terms of converter parameters. Finally, the proposed IMS concept is validated through a 300 W, 100 V to 168 V prototype, switching at 70 kHz.

Automated Identification of Failures in Doubly-Fed Induction Generators for Wind Turbine Applications

Remote, automated monitoring of wind generators is crucial considering that wind turbines are prone to failure due to the harsh operating environment, and difficult to access or test due to the remote location of wind turbines. The demand for condition monitoring of wind generators is increasing with the rapid growth in wind power generation. In this work, a new inverter-embedded off-line test concept for automated testing of doubly-fed induction generators (DFIG) is proposed for detection and classification of defects in the 1) slip ring-brush contact, 2) rotor winding turn insulation, and 3) stator core inter-laminar insulation. The main idea is to use the rotor side inverter for injecting test signals into the rotor winding for detecting asymmetry in the machine, whenever the DFIG is at standstill. The pattern of asymmetry in the equivalent impedance as a function of angle is analyzed for identifying the presence and type of DFIG fault at an early stage for efficient scheduling of maintenance. Experimental verification is given to show that the proposed test provides a simple means of identifying DFIG faults with high sensitivity and reliability without additional hardware.

Concept and Process Development Using Ex Situ Fabricated High-Density Interconnect Plugs for Circuit-Board Embedded Magnetic Components

Magnetic circuit components have long been the largest and most difficult components to miniaturize. Printed circuit board (PCB) fabrication methods cannot achieve small diameter, high aspect-ratio vias for high winding turn numbers to achieve high inductance, and microelectronics methods cannot achieve the high-quality and thick ferrite core materials. In this paper, we present an alternative breakthrough method of printed circuit fabrication to significantly reduce the effective via diameter for embedded magnetic devices, boosting the inductance per unit area. To reduce the effective via diameter, high-density via plugs are ex-situ fabricated and shaped, and then embedded into PCB substrate in the same process as standard magnetic core embedding. The structure of the plug is such that precise placement within the substrate, or alignment to the plug with the winding pattern, is not necessary. Devices presented in this paper use via plugs with an effective diameter of 40 μm and a theoretically unlimited aspect ratio, though refinements in the plug fabrication process are expected to reduce the via diameter down to 10μm. The process is experimentally demonstrated with a 14-turn racetrack shaped transformer; novel diagnostic methods using magneto-optic garnet films to image current paths are also demonstrated.

A study on electrical properties of silicon carbide power devices

Silicon Carbide (SiC) devices have the characteristics of high voltage resistance, fast switching speed, high working frequency, small on-resistance, and high-temperature resistance, and have broad application prospects in high voltage and high-power occasions. However, the application of SiC is faced with the problems of high-frequency switching transient voltage, current overshoot, ringing, and short circuit protection. Based on the problems encountered in the application process of SiC power devices, the characteristics and drive protection technology of sic devices are studied in this paper. In this paper, the static characteristic parameters of SiC device are studied, the switching characteristic parameters are tested, the influence of parasitic inductance parameters on the switching characteristic is analyzed, and the design method of PCB Roche coil is analyzed, the anti-interference performance of loop winding turns is analyzed and the driver protection circuit is designed.

Improving the energy efficiency of wind turbines for charging batteries

The article describes the method for determining the optimal angular velocity and the number of turns of the generator winding on permanent magnets powered by a wind turbine operating in specific operating conditions according to the wind speed regime. The optimization criterion is the maximum potential of energy that can be used to charge the battery. The permissible power of the generator and wind turbine, current and battery charging voltage are accepted as limiting factors. The restriction is provided by connecting a ballast resistor to the generator output. The power developed by the turbine is determined taking into account the wind energy utilization factor, which depends on the angular velocity of its shaft and wind speed. Two variants of power limitation are compared: by limiting the angular velocity by aerodynamic means and by stopping the wind turbine. The return of energy to charging in both cases is determined taking into account the distribution of wind speeds, obeying the Weibull probability distribution law. As an example, the calculation of the possible annual power generation for charging a battery with a capacity of 200 A∙h with a voltage of 24 volts from a synchron generator with a number of poles of 48 driven by a wind turbine with a radius of 2 meters, operating in an area with an average wind speed of 5 m/s. The calculation shows that for the parameters and operating conditions of the electrical installation used in the example, the maximum annual energy output (3.3 × 103 kWh) is observed at optimal 11 turns of the winding at each of the poles of the generator. The deviation of the number of turns from the optimal one in both directions by 2 times leads, with the same dimensions of the wind turbine, to a decrease in annual energy output by 3...5 times, which is a clear proof of the need to carry out such a calculation for each specific wind turbine.

Theoretical and Experimental Analysis of a Winding Rope Fluid Viscous Damper

This paper investigated a winding rope fluid viscous damper (WRFVD) that uses the frictional amplification mechanism of a winding rope to obtain the operating characteristics of a viscous damper-like device. The WRFVD combined the advantages of fluid viscous dampers and friction dampers. It not only retained the mechanical characteristics of the fluid viscous damper but also reduced manufacturing costs. First, the construction and working principles of the WRFVD were introduced. A theoretical model that could accurately simulate the hysteretic characteristics of the damper was derived. Then, a series of dynamic tests were performed on six prototypes of the WRFVD. The dynamic performance under different displacement amplitudes and device parameters was analyzed based on the test results. In addition, the theoretical model was validated by experimental results. Finally, a series of parametric analyses of the WRFVD were performed. The experimental results showed that the WRFVD is a type of velocity-dependent damper with smooth and plump hysteretic curves under sinusoidal displacement excitation. Fatigue loading tests showed that the WRFVD had excellent fatigue resistance capacity and stable operational performance. The established theoretical model was reasonable and satisfactorily reproduced the hysteretic properties of the WRFVD. The parametric analyses showed that it was not recommended to improve the performance of the WRFVD by the method of adjusting the damping coefficient and pretightening load. It was reasonable to adjust the performance of the WRFVD by setting a smaller velocity exponent, an appropriate winding turn of winding ropes, and a suitable friction coefficient.

A Sensor for the Ultraweak DC Current Covered by Strong AC Currents

In the field of insulation monitoring of high-voltage power equipment, the dc leakage current is an important indicator to evaluate the insulation state. However, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> -level dc leakage currents are usually mixed with mA-level power-frequency ac currents, bringing obstacles to the accuracy of the dc measurement. In this regard, a new magnetic modulator with a suppressing structure is proposed. Based on the fact that Lenz law only keeps valid for a changing magnetic flux, the ac suppressing structure is developed to enclose the original magnetic modulator. Then, the factors of the suppression structure’s performance, including weakening the ac magnetic flux and reducing the dc measurement sensitivity, have been analyzed. And the performance is found to be closely related to the magnet dimensions, the magnetic permeability, and the suppressing winding turns. Finally, the improved prototype current sensor for the converter transformer valve side bushing has been developed, and experiments are conducted to verify its dc accuracy and ac suppressing performance.