Magnet Wire Research Articles

Impedance-based Health Monitoring of Electromagnetic Coil Insulation Subjected to Corrosive Deterioration

Electromagnetic coils are widely used components in a variety of industries and systems, and their failure can lead to catastrophic failure of the system in which they are placed. Past studies have revealed the electromagnetic coil insulation to be a weakness, and there are presently no available methods to detect degradation in the coil insulation in-situ. Prior work in the AC motor community on twisted pairs of magnet wire has shown that insulation capacitance measurements can reveal useful diagnostic information. Yet, no studies have tracked the coil impedance spectrum over an aging/degradation period, no methods are available to identify frequencies in the impedance spectrum to be used, nor is there discussion concerning methods to employ coil impedance to determine a degradation mechanism. This paper develops an approach of detection of the aging of insulation in low-voltage electromagnetic coils when subjected to corrosive environmental conditions by assessing changes in impedance responses. The complex impedance was resolved into its real and imaginary parts and the Spearman correlation coefficient was used to find regions of interest within the impedance spectrum. The results indicate that real and imaginary impedance provide information that can assist in condition-based maintenance procedures for electromagnetic coils. Furthermore, by incorporating frequency-correlation analysis, the individual frequencies which provide diagnostic and prognostic information can be identified.

JOULE HEATING EFFECT REDUCTION OF AN ELECTROMAGNET SYSTEM UTILIZING ON-CHIP MAGNETIC CORE

Joule heating effect is substantial in an electromagnet system due to high density current from current-carrying conductor for high magnetic field generation. In Lab-on-chip (LoC) Magnetically Activated Cell Sorting (MACS) device, Joule heating effect generating high temperature and affecting the biological cells viability is investigated. The temperature rise of the integrated system was measured using resistance temperature detector, RTD Pt100. Three temperature rise conditions which are from the bare spiral-shaped magnet wire, the combination of magnet wire and on-chip magnetic core and combination of magnet wire, on-chip magnetic core and 150 mm polydimethylsiloxane (PDMS) layer have been investigated. The combination of electromagnet of spiral-shaped magnet wire coil and on-chip magnetic core has reduced the temperature significantly which are, ~ 38 % and ~ 26 % with magnet wire winding, N = 10 (IDC = 3.0 A, t = 210 s) and N = 20 (IDC = 2.5 A, t = 210 s) respectively. The reduced Joule heating effect is expected due to silicon chip of high thermal conductivity material enable fast heat dissipation to the surrounding. Therefore, the integration of electromagnet system and on-chip magnetic core has the potential to be used as part of LoC MACS system provided the optimum operating conditions are determined

Effect of direct fluorination on partial discharge characteristics of polyimide film used as magnet wire insulation of generator

Polyimide (PI) film is widely used as the insulation between coils in generator, where partial discharge (PD) may occur to cause the insulation breakdown. Fluorination is considered as an effective method for surface modification of polymer materials to change its electrical properties. In this study, to study the effect of fluorination on the PD behaviour of PI film used as magnet wire insulation, the samples of magnet wire were covered by PI film. Samples were fluorinated in a reaction kettle using the F2/N2 mixture for different time. The non-fluorinated and fluorinated samples were subjected to partial charges under alternating electric field. A wideband detection system was used to detect PD waveform and record discharge phenomenon. The experimental results indicate that the direct fluorination has great effects on the surface charge accumulation and the decrease in PD intensity. The magnet wire fluorinated for 45 min shows the highest PD inception voltage, the lowest intensity of successive discharges and the smallest number of discharge pulses.

Critical Performance Analysis of HTS Magnet Wires Using an Induced Current-Based Measurement System

Studies on wide and stacked high-temperature superconducting (HTS) wires aim to increase the critical current of the wires. This paper describes the design and fabrication of an induced current-based performance measurement system and a critical performance analysis of HTS magnet wires using this system. In the experiment, the induced current, critical current, and joint resistance of stacked HTS wires under charge and discharge conditions were investigated. The results obtained were compared with those achieved using the four-terminal method, which is the conventional measurement method. The measurement system and the results of the critical performance analysis of the HTS wire are discussed in detail.

Theoretical determination of the strength characteristics of multilayer materials intended for nuclear and thermonuclear engineering

A method is developed to estimate the integrity of multilayer structures. This method is based on the version of the theory of adhesion and cohesion interactions of structure elements that only takes into account their thermomechanical properties. The structures to be studied are the material of the multilayer wall of the liquid-metal thermonuclear reactor blanket and a heat-resistant magnet wire with a bimetallic conductor, which is the base of the windings of the magnetohydrodynamic machines and electric motors intended for operation at high temperatures under ionizing radiation in, e.g., the machines and facilities in nuclear and thermonuclear reactors.

Novel butt-lapped PET-mica tape turn insulation for high voltage motors

Turn insulation for high voltage motor coils is normally a glass cloth–backed mica paper tape that is applied to the magnet wire according to specified fabrication methods [1]–[4]. In contrast to the main insulation, turn insulation is much thinner and more easily damaged during production because there are many processing steps. Hence, there is more attention paid to the protection of the turn insulation. Conventionally, turn insulation is protected with a double glass yarn that is applied to the wires [5]. For example, turn insulation for 6-kV motors is lapped with a double layer of glass yarn plus polyimide film, and for 10-kV motors, a double layer of glass yarn plus PET-mica tape is used. However, these conventional turn insulations have several drawbacks; namely, the turn insulation is easily damaged during coil production, and impregnation of vacuum-pressure impregnation (VPI) resin is poor [6]–[9]. Hence, it is desirable to eliminate the glass yarn insulation layer and use PET-mica tape directly as the turn insulation, which also has the additional advantages of good mechanical properties, good impulse strength and corona resistance, better voltage endurance, and lower cost.

Optimization of Magnetizing Parameters for Multipole Magnetic Scales Using the Taguchi Method

Magnetic encoders are widely used to identify the position or travel distance in machine tools in a harsh environment. A magnetic encoder comprises a magnetic sensor and a magnetic scale, which is a permanent magnet strip magnetized into a multipole configuration. The pole pitch, magnetic flux density, periodicity, and symmetry of a magnetic field pattern are crucial for signal processing to obtain a satisfactory resolution. The magnetic flux density and the accuracy of a magnetic scale with a qualified permanent magnet strip are determined using magnetization technology. This paper focused on the optimization of perpendicular magnetizing parameters, using the Taguchi method, for designing a magnetizer to fabricate the high-quality magnetic scales made of rubber magnets. The parameters included the thickness of the magnetizer core, diameter of the magnet wire, magnetizing current, and magnetizing gap. The optimal parameters of magnetization were determined, and the reproducibility was validated. The average magnetic flux density was increased by $\sim 17$ % after optimization. In addition, the high-quality magnetic field pattern was achieved and it was advantageous for signal processing.

Flow and heat transfer of non-Newtonian fluids in enameling dies

A widely used technique for the coating of magnet wires is passing them through enameling dies, from which they exit with a defined layer of enamel deposited on their surface. The generalized Couette flow, which emerges inside the converging annular gap between the moving wire and the stationary wall of the die, is computationally analyzed using the lubrication theory approximation. Non-Newtonian flow behavior and heat transfer are considered as well. The obtained results give a detailed insight into the effects of shear thinning/thickening on the velocity field and the wall shear stress along the wire. Despite the intense generation of viscous heat in the highly sheared region, the still moderate increase in temperature of the enamel does not pose any possible cooling problem. The influence of the die geometry on the drag force on the wire is examined by varying the axial contraction of the die, whose shape is assumed to follow a cosine-type function. The applied changes in the die geometry produce the same trends in the resulting drag force for all considered rheologies. The targeted reduction in the drag force could be achieved with the same die shape regardless of the flow behavior of the fluid. The predictions obtained from the lubrication theory based analytical model were validated against numerical results from computationally much costlier CFD simulations. This assessment proved the analytical model as a computationally efficient and reliable approach to describe the flow inside the die also for the fairly complex case of a shear thinning non-Newtonian fluid with temperature dependent viscosity.

Optimal Design of Magnetorheological Fluid Damper Based on Response Surface Method

A B S T R A C T In this research, the effect of shape parameters such as number of magnet wire turns, spools, thickness of the gap, and pole length in a Magnetorheological (MR) fluid damper is analytically investigated and the optimization of these parameters is done with response surface method (RSM) which is combined Neuro-Fuzzy method and Particle Swarm Optimization (PSO) algorithm. Since the electromagnetic and mechanical components of a Magnetorheological (MR) fluid damper have a direct effect on the electrical power consumption, time delay, and damped force that are considered as objective functions. Because of the nonlinear behavior of the components, a robust approach is needed to predict their reactions; therefore, Neuro-Fuzzy is utilized to generate a high accurate surface and PSO finds the optimum solution base on the surface. The sensitive analysis is also performed to examine the variation of the objective functions with various input parameters. In this process, the best parameters are obtained by overtaking the appropriate value of the objective functions. The results demonstrate that the optimum MR damper has provided the best configurations, so that damps a maximum force in minimum time and lowest power consumption. On the other hand, the amplitude of vibrations is significantly decreased in the presence of the optimized MR damper. doi: 10.5829/idosi.ije.2015.28.09c.14

The Research of Energetic Characteristics of Induction Smelting Crucible Furnaces

Induction smelting crucible furnaces have the advantage of optimal management of the process, regulation of the capacity and have high technical indices. The research of electrical and energetic correlation of induction smelting crucible furnaces is necessary in order to analyze the work and elucidate the optimal condition of exploitation, to work out the methods of projection and determine the optimal constructions of magnet wires. The authors worked out the methods of calculating the energy of electromagnetic field according to the sections of the space of the induction system, to the selection and installation of magnet wires in order to meet the technological requirements in the best way and to achieve high energetic and exploitation indices when building the induction crucible furnaces. The work represents the influence and interrelation of the inductor and the charge with the magnet wire depending on geometrical correlation of the induction system.

Application of Phosphate Process in Ceramic Insulated Magnet Wire

In this paper we take advantage of the phosphate film which has a porous structure, by phosphate process on the surface of nickel plated copper conductor so as to improve the bonding force of wire and ceramic layer; Through the study of resistance voltage breakdown after phosphate , phosphate liquid was determined Manganese dihydrogen phosphate for 3g100-1ml, Zinc Nitrate was 8g100-1ml, Sodium Fluoride was 0.45g100-1ml; Optimum temperature was 60°C and the appropriate time was 15min at the temperature of 60°C.

Speed Synchronization System of Master-Slave Motor Based on Repetitive Control

In the wrapping process of magnet wire, as the haulage speed of master motor varies periodically, it is difficult for slave wrapping motor to track master motor due to the mechanical resonance, which destabilizes the wrapping pitch. In the proposed system, the synchronization speed control scheme of master-slave motor based on repetitive control compensation is employed. In the process of control, real-time spectrum analysis of the haulage speed is given, which can be used to adjust the parameters of wrapping speed controller adaptively with the acquired characteristic information of the mechanical resonant. Simulation shows that wrapping speed can track haulage speed well in the proposed system, and the maximum tracking synchronous deviation can be reduced to 56% of that in the system without repetitive control.

Ventilation Fan Fires: Overheated Windings Lead to Failed Thermal Limit Switch

Over the last several years, the forensic community has experienced an increase in the number of fires which have been attributed to ventilation fans. These failures have been anecdotally observed in Jakel motors, specifically model numbers J239-050-5138 and J238-050-5494, manufactured between 2000 and 2003. While there have been a number of variations to motors within exhaust fans over the preceding decades, including different winding size, winding metal, and thermal cut-off (TCO) manufacturers, two design implementations have led to the higher incidents of failure. The first design change is the implementation of 27 American Wire Gauge aluminum winding (magnet) wire. The second, and most important, is the implementation of the Tamura Thermal Device Corporation (TAM) TCO to replace the Elmwood Sensor/Honeywell (Elsen) TCO. Through investigations and testing, the Tamura TCO has been found to be unreliable at opening the circuit within the motor when exposed to temperatures above its specified cut-off temperature (136°C). Thermal testing of a Tamura TCO showed that even when exposed to temperatures as high as 260°C, the flux of the fusible thermal link is incapable of breaking down the oxides created by the metal alloy. The hypothesized failure mechanism for the Tamura TCO include increased exposure to high temperatures during fan operation and/or air infiltration from cracks in the epoxy sealant due to improper installation, along with the corrosive effects of the chlorinated flux. This work presents case studies, experimentation, and analysis of the failure mechanisms related to fires associated with the aforementioned motors.

Estimation of partial discharge inception voltage of magnet wires under inverter surge voltage by volume-time theory

This paper discusses a novel estimation method for partial discharge inception voltage (PDIV) of magnet wire under inverter surge voltage application. We focused on the generation probability of initial electrons, which induce PD under high electric field and short rise time of surge voltage, by means of Volume-Time theory. We applied the Volume-Time theory to PD inception phenomena in a wedge-shaped air gap of twisted pair samples composed of enameled wires, and estimated PDIV in consideration of initial electron generation probability with temporal and spatial change in electric field distribution. We could estimate PDIV under different waveforms of applied surge voltage for different specifications of enameled wires. PDIV estimated by the extended Volume-Time theory agreed well with the measured PDIV. The estimated PDIV decreased with the increase in the rise time of applied voltage waveform, which corresponded to the V-t characteristics in the time range of inverter surge voltage.

Inverter surge resistant enameled wire with nanocomposite insulating material

An inverter surge resistant enameled wire was developed with innovative organic/inorganic nanocomposite insulating material by dispersing an inorganic material at a nanometer level. It successfully achieved satisfactory levels for both partial discharge resistance and coating film flexibility and strength. This product can maintain a voltage endurance of more than 1000 times as high as those offered by general enameled wires even after mechanical stress is applied. This paper describes how the product can dramatically improve the reliability of magnet wires and open the way for performance warrant of inverter-fed motors in actual operation up to a surge voltage around 1.5 kVp.

Considerations on Application of Surge-proof Magnet Wire for Inverter-fed Random Wound Motors

This paper discusses the lifetime evaluation of twisted pairs which was constructed by a surge proof magnet wire. Two kinds of twisted pairs were constructed; one is a conventional twisted pairs and the other is a special twisted pairs which has varnish treatment at both edge sides of it. The both lifetime characteristics were evaluated and the breakdown positions were also investigated. As a result, it was found that the lifetime of the edge parts of usual twisted pairs was about 50% shorter than that of the other positions. It was estimated that the partial discharge activity at the edge part is stronger than that at the other positions, by an ultraviolet light measurement or others. This paper also describes a concept and quality control method for the inverter fed random wound motor which was manufactured by using a surge proof magnet wire.

Electrical Treeing Breakdown Properties for Polyimide Nanocomposite Film in Inverter-Fed Motors

The failure of magnet wires used in inter-turn insulation of inverter-fed motor winding is the main cause which leads to the motor insulation breakdown. This paper conducted electrical tree breakdown experiments on magnet wire insulating film (FCR 100) used in the inter-turn insulation of JD117 inverter-fed motor and meanwhile combining with energy spectrum analysis and scanning electrical microscope (SEM), by which type and content of elements, breakdown main body and electrical tree channel could be clearly observed, the corresponding failure mechanisms were analyzed. The experiment results reveal that all the breakdown main bodies are located at the pointedness and insulation joint of magnet wires, of which dielectric strength is relatively lower; they are the insulation “weak point”, which should be paid enough attention and strengthened at the manufacturing period. The electrical tree breakdown time is quite long and the life span of magnet wire is 11 hours. The electrical breakdown strength of envelope is very low when containing metal impurity. It is also found that the aluminum occupies the highest content tested by energy spectrum analysis.

Multifactor Stress Life Model of Polyimide Film Used in Inverter-Fed Traction Motors

The inverter-fed traction motor is one of the key components in the locomotive. However, the motor insulation failures have repeatedly occurred in premature. The failure mechanism for insulation under continuous impulses is different from that under sine waves. The single stress approach in design stage and also in ageing studies offers relative simplicity, but it is inapplicable to real life operating conditions which mostly are of multi-stress type. In this paper, a novel test apparatus of insulation failure time was designed for accelerating aging test. Meanwhile, electrical breakdown experiments on magnet wire insulating polyimide film (FCR 100) used in the inter-turn insulation of JD117 inverter-fed motor was conducted. The effects of multi-stress including impulse amplitude-temperature and impulse frequency-temperature were investigated respectively. The test results under different conditions were analyzed based on statistic analysis of Weibull distribution. Finally, insulation life models under combined thermal and electrical stresses were proposed using the multi-stress approach. A fitted formula for ageing life was presented which had two independent variables of voltage and temperature. The generality of the model lies in the fact that it can be used for designing of insulation system of all electrical components containing solid insulating materials surrounded by gas. Since the model is based on the probability of insulation deterioration under the action of the stresses applied, that gives us the opportunity to calculate the life time of insulation system for given system of stresses, the materials selected and the requested probability of failureless system operation.

The convective drying of liquid films on slender wires

We solve numerically the balance equations of mass and thermal energy for drying liquid films of binary solutions on cylindrical substrates to simulate the drying process of liquid coatings on round metal wires, which are used for electrical insulation in magnet wire technology. The liquid phase diffusion coefficient and the solvent activity are treated as concentration and temperature dependent. The evaporation rate of the solvent across the shrinking liquid–gas interface is determined using the film theory, accounting for the thermodynamic state of the ambient medium and the convective flow situation. The quality of the coatings is assessed by the temporal evolution of radial profiles of the solute mass fraction and by detecting boiling, which leads to the formation of vapour bubbles in the liquid films and is undesired. A guideline for uniform drying at various drying conditions is presented. The simulation model is applied to the test system PVA-water.

Exploring Magnetic Fields with a Compass

A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this paper, we present a series of simple activities adapted from the Matter & Interactions textbook1 for doing just this. Interestingly, these simple measurements are comparable to predictions made by the Bohr model of the atom. Although antiquated, Bohr's atom can lead the way to a deeper analysis of the atomic properties of magnets. Although originally developed for an introductory calculus-based course, these activities can easily be adapted for use in an algebra-based class or even at the high school level.