Experiment and numerical simulation of the combined effect of winding, cool-down, and screening current induced stresses in REBCO coils

This paper overviews the combined effect of winding, cool-down, and screening current-induced stresses in REBCO coils. First, a simulation method to model the circumferential stress modification effect due to the screening-current is overviewed. The simulation includes coil winding, cooling down, and coil charge up to the operating current. Second, we will compare the numerical simulation results with the experimental results. The numerical simulations for a dry coil and an epoxy impregnated coil agree well with the experimental results. Third, the enhanced circumferential stress did not degrade the performance of a dry winding REBCO coil, but. the improved increased compressive stress buckled the coil structure. Finally, it is demonstrated that epoxy impregnation has beneficial effects in reducing the stress modification effect. However, the circumferential stress is enormously enhanced at the coil ends, sometimes resulting in degradation of the coil performance.

Development of an Advanced Sham Coil for Transcranial Magnetic Stimulation and Examination of Its Specifications

Transcranial magnetic stimulation (TMS) neurophysiology has been widely applied worldwide, but it is often contaminated by confounders other than cortical stimulus-evoked activities. Although advanced sham coils that elaborately mimic active stimulation have recently been developed, their performance is not examined in detail. Developing such sham coils is crucial to improve the accuracy of TMS neurophysiology. Herein, we examined the specifications of the sham coil by comparison with the active coil. The magnetic flux and click sound pressure changes were measured when the stimulus intensity was varied from 10% to 100% maximum stimulator output (MSO), and the changes in coil surface temperature over time with continuous stimulation at 50% MSO for each coil. The magnetic flux change at the center of the coil showed a peak of 12.51 (kT/s) for the active coil, whereas it was 0.41 (kT/s) for the sham coil. Although both coils showed a linear change in magnetic flux as the stimulus intensity increased, due to the difference in coil winding structure, the sham coil took less than half the time to overheat and had 5 dB louder coil click sounds than the active coil. The sham coil showed a sufficiently small flux change at the center of the coil, but the flux change from the periphery of the coil was comparable to that of the active coil. Future use of high-quality sham coil will extend our understanding of the TMS neurophysiology of the cortex at the stimulation site.

Effects of Resin/Filler Adhesion on the Thermal and Electrical Conductivity of Polyimide Nanocomposites

With an aim to develop a good coil winding insulation film, fillers of boehmite alumina in the shape of a roughly rectangular plate were added with ratios of 10 and 20 wt% to polyimide. The filler surface was untreated or treated with a methacrylic or an epoxy silane coupling agent. Such prepared polyimide nanocomposites were subjected to various tests to measure the tensile strength, elastic modulus, complex permittivity, and thermal conductivity. It was found that samples with fillers treated using the methacrylic silane coupling agent have the strongest adhesion at the filler/polyimide interfaces and the lowest dielectric loss factor at high temperatures. A positive relationship between the filler/polyimide adhesion and the thermal conductivity is also indicated. These findings are significant since they indicate that the adhesion status at the filler/polymer interface exerts a strong influence on the thermal and electrical conduction processes in the polymer.

Design of Insulation Tape Tension Control System of Transformer Winding Machine Based on Fuzzy PID

With the rapid development of science and technology as well as the comprehensive societal progress, the demand for electricity in all walks of life is also increasing. As is known to all, the mechanical structure and tension control of a transformer winding machine is the key to improving the quality of coil winding, due to coil winding being generally considered the core technology of transformer manufacturing. Aiming at the synchronous winding control problem of the conductor and insulating layer of the transformer winding machine, this paper presents a mechanical structure and tension control scheme of a new type of transformer winding machine. Based on the dynamic analysis and modeling of the mechanical structure of the winding machine, the speed control of the main speed roller by the fuzzy PID control rate is implemented initially. Combined with the actual demand of the project, the feasibility and effectiveness of the control target with different tension are verified by the simulation experiment and further compared with the traditional PID control method. The simulation results show that the proposed fuzzy PID control rate can realize the automatic and efficient winding of the transformer winding machine, showing that it is superior to the traditional PID control rate in overcoming the disturbance and controlling effect.

Modelling Interdependencies in an Electrical Motor Manufacturing Process Involving Deformable Material

Electrical machines have recently received a lot of attention due to a variety of applications in several industries. Although advances in digital technologies have enabled more efficient production of electrical machines, faults are still identified at the end of the line tests. In order to avoid accumulation of defects during the production chain, it is desirable to identify faults early in the process. This can be achieved by identifying how critical process parameters and the interdependencies between them influence the occurrence of faults. This poses a challenge in electrical machine manufacturing because of the complexity involved in various manufacturing steps involving deformable material, an example is coil winding. This paper proposes a computational framework to model interdependencies in a complex electrical machine manufacturing process involving deformable material. A Discrete Event Simulation model representing the coil winding process demonstrated that input parameters such as wire tension and winding speed influence physical and electrical properties of the coil (enamelled copper wire) leading to generation of defects in the final product.

Express Wire Coil Cladding (EW2C) as an Advanced Technology to Accelerate Additive Manufacturing and Coating

Metal shafts are indispensable components in mobility, energy and mechanical engineering. In such applications, the shafts need to withstand severe mechanical loads, friction, high temperature or corrosive media. This is why shafts are often completely made of high-performance alloys. From a technical point of view, coating an inexpensive base shaft with a thin layer of high-performance material is mostly sufficient to ensure its functionality. Adding functional parts such as bearing seats by Additive Manufacturing (AM) is an advantageous approach to increase flexibility and material efficiency. Reliable and economic AM processes need to be developed further, and laser-based processes such as wire-based Laser Metal Deposition (LMD-w) offer high potential to accomplish this. Due to their low deposition rate, however, LMD processes are not economically competitive with high-speed subtractive technologies. Motivated by this challenge, we present an alternative approach for laser-based shaft cladding. Instead of adding the filler wire continuously, wire coils are wound and preplaced on the shaft. In a second step, laser processing while rotating the part generates a metallurgical bond between the wire and the substrate. In this study, several solid and flux-cored wires were analyzed regarding their suitability for this two-step coil winding and LMD process. The resulting surface state and the welded joint quality are evaulated. Metallographic cross sections show low porosity and small heat-affected zones. Thanks to its good scalability, this innovative process can help strongly increase the build-up rate compared to classic LMD-w.

Design and fabrication of a portable automatic coil winding machine

Purpose The difficulty in winding coil-based electrical and electronic devices manually lies in the fact that it takes so much time and effort to perform. Furthermore, it is difficult to achieve accuracy manually, as it is possible to lose count of the number of turns being wound. The purpose of this paper is to detail the design methods and calculations used to achieve a cost-effective, significantly accurate and more efficient method of winding coils. Design/methodology/approach A program flowchart was designed as a guideline for writing the program. An AT89C52 microcontroller was used to control the movement of the two direct current (DC) motors used in the construction of the machine. The circuit design obtained was then simulated using Proteus to test the functionality of the components together. Findings An electromechanical automatic coil winding machine for the coiling of simple, small-sized, coil-based electrical devices was successfully designed and fabricated. The machine was tested by winding a 1 kVA transformer. Diagrams, calculations, results and observations obtained during the design and construction are detailed in this paper. Originality/value This machine solves the problem of tediousness in coil winding, stably and precisely winding 60 turns/min at a 24 V supply and providing a keypad input method. Although portable automatic coil winding machines have been rendered previously, most have applied the use of stepper motors. The application of brushed DC motors alongside an AT89C52 microcontroller is a variation to the pool of renditions, offering better controllability and a sustained output.

A Complex Study of Stator Tooth-Coil Winding Thermal Models for PM Synchronous Motors Used in Electric Vehicle Applications

The operational reliability and high efficiency of modern electrical machines depend on the ability to transfer heat in the construction parts of the machine. Therefore, many authors study various thermal models and work on the development of effective heat dissipation. New insights and methods lead to improved techniques for the thermal design of electrical machines. This paper presents an experimentally validated thermal model of a permanent magnet synchronous motor (PMSM) with an improved slot winding model. It also deals with various approaches to homogenization and equivalent material properties of a tooth-coil winding sub-model. First, an algorithm for building a lumped-parameter thermal network (LPTN) of PMSM is described and its properties and problems are discussed. Subsequently, a sub-model of a slot with a winding based on the finite element method (FEM) is introduced. This sub-model is able to generate different conductor distributions based on probabilistic methods for a specified fill factor. This allows the verification of various homogenization approaches and at the same time it is a tool that automatically calculates thermal resistances for the LPTN.

Analysis and evaluation of temperature field and experiment for magnetorheological fluid testing devices

When a large amount of heat is produced during the operation of a MRF (magnetorheological fluid) testing device, the temperature of the device will increase, which will in turn affect the characteristics of the MRF. Exploring the temperature field characteristics of the MRF yield stress testing device is necessary to improve the accuracy of the device. In this study, first, the yield stress testing device is designed, and then its temperature field model, including enameled wire and assembly gap, is established. Second, simulation software is used to simulate the temperature field change. Finally, a test platform is developed to test the simulation results, especially for two factors, namely, thermal conductivity of the coil winding and assembly gap, which demonstrate considerable influence. Comprehensive thermal conductivity and assembly clearance are determined, and the optimum temperature field of the device for measuring yield stress is resulted.