Real Coil Research Articles

Online Crack Detection of Highly Curved Cylindrical Coils

Many vision-based methods for defect detection have been proposed to replace inefficient manual inspection. However, due to the complex shape and high degree of freedom required to manipulate individual coils, an automatic optical inspection (AOI) method for cylindrical coils remains unsuccessful due to the difficulty of automatically scanning the front, rear, outer, and inner faces of complex spiral-shaped cylindrical coils. This paper presents a turnkey integrated system that can be operated in real time for real coil manufacturers. First, a novel 1-degree-of-freedom rotational progressive system is designed to automatically transport and sort individual spiral coils. Second, a multisensor imaging system is designed to capture images of 360° panoramic views of a cylindrical coil. Then, a robust automatic defect detection algorithm consisting of crack detection and geometric measurement is developed to detect defects in cylindrical coils during manufacturing procedures. The results of a large-scale validation experiment indicate that the proposed AOI system is robust and is practically immune to variations in surface normal vectors, occlusion, and defocus blur, and it has a high sensitivity and specificity of 99.75% and 94.2%, respectively. This validation experiment proved that the software and hardware designed in this study can implement defect detection of spiral coils.

Application of synthetic data in the training of artificial intelligence for automated quality assurance in magnetic resonance imaging.

Magnetic resonance imaging scanner faults can be missed during routine quality assurance (QA) if they are subtle, intermittent, or the test being performed is insensitive to the type of fault. Coil element malfunction is a common fault within MRI scanners, which may go undetected for quite some time. Consequently, this may lead to poor image quality and the potential for misdiagnoses. Daily QA typically consists of an automated signal to noise ratio test and in some instances this test is insensitive to coil element malfunction. Instead of relying on daily QA testing, it was proposed to utilize patient images in conjunction with a trained neural network to detect coil element malfunction, even when it presents as a very subtle defect. The advantage to using patient images over phantom testing is real-time monitoring can be achieved. This allows clinical staff to focus more on patient throughput without being burdened by daily testing. A neural network was trained using simulated coil failure in 3958 abdominal or pelvic images from 497 patients. The accuracy of the trained network was then tested on an unseen dataset of 109 images from which 44 patients which had coil element malfunction present. Five MRI radiographers were shown 249 images with and without real coil malfunction to assess their accuracy compared to the neural network in identifying the scanner fault. The neural network achieved an accuracy of 91.74% in identifying coil element malfunction in the unseen data. Radiographers tasked with identifying coil element malfunction had an average accuracy of 59.99%. In the same test case, the neural network outperformed all radiographers with an accuracy of 91.56%. This work demonstrates that neural networks trained with artificial data can successfully identify MRI scanner coil element malfunction in clinical images. The method provided better accuracy than MRI radiographers (technologists) at identifying coil element malfunction and highlights the potential utility of AI methods as an alternative to support traditional QA. Further, our methodology of training neural networks with simulated data could potentially identify other faults, allowing centers to produce robust fault detection systems with minimal data.

Effect of high-frequency repetitive transcranial magnetic stimulation under different intensities upon rehabilitation of chronic pelvic pain syndrome: protocol for a randomized controlled trial

IntroductionNearly one in seven women worldwide suffers from chronic pelvic pain syndrome (CPPS) each year. Often, CPPS necessitates a combination of treatments. Studies have shown the good therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) upon CPPS. We wish to undertake a randomized controlled trial (RCT) to observe the effect of high-frequency rTMS at different intensities upon CPPS.Methods and analysesIn this prospective, double-blinded RCT, 63 female CPPS participants will be recruited and randomized (1:1:1) to high-intensity rTMS, low-intensity rTMS, or sham rTMS. The control group will receive a 10-day course of conventional pelvic floor (PF) rehabilitation (neuromuscular stimulation, magnetic therapy, or light therapy of the PF). On the basis of conventional treatment, participants in the high-intensity rTMS group will receive pulses of 10 Hz with a resting motor threshold (RMT) of 110% for a total of 15,000 pulses. Participants in the low-intensity rTMS group will receive pulses of 10 Hz with an RMT of 80% with 15,000 pulses. The sham rTMS group will be subjected to sham stimulation with the same sound as produced by the real magnetic stimulation coil. The primary outcome will be determined using a visual analog scale, the Genitourinary Pain Index, Zung Self-Rating Anxiety Scale, and Zung Self-Rating Depression Scale. The secondary outcome will be determined by electromyography of the surface of PF muscles at baseline and after treatment completion.Ethics and disseminationThis study is approved by the Ethics Committee of Bao’an People’s Hospital, Shenzhen, Guangdong Province (approval number: BYL20211203). The results will be submitted for publication in peer-reviewed journals and disseminated at scientific conferences (Protocol version 1.0-20220709).Trial registrationChictr.org.cn, ID: ChiCTR2200055615. Registered on 14 January 2022, http://www.chictr.org.cn/showproj.aspx?proj=146720. Protocol version 1.0-20220709.

Development of a 120-mm Aperture Nb3Sn Dipole Coil With Stress Management

This paper describes a 120-mm aperture 2-layer dipole coil with stress management (SM) developed at Fermilab based on cos-theta coil geometry. A model of the coil support structure made of plastic was printed using additive manufacturing technology and used for practice coil winding. The real coil support structure was printed using the 316 stainless steel. The results of the SM structure size control and the key coil fabrication steps are reported in the paper. The design of coil SM structure and the coil FEA in the dipole mirror test configurations are presented and discussed.

Thermal Runaway of Conduction-Cooled Monofilament and Multifilament Coated Conductors

We experimentally studied the thermal runawayinitiating at a low critical current ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) part. This low <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> part is determined by the combination of two reasons in a real coil: (a) the unavoidable defects caused by the manufacturing process, which reduce local critical currents (and might not be uniform across the width of a coated conductor) and (b) the magnetic field distribution along the coated conductor. To simulate the thermal runaway using a short monofilament/multifilament REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> (RE-123) coated conductor, we artificially created a local defect (low <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> part) in a short sample by pressing using a drill bit (creating a defect close to one edge of a coated conductor) or bending (creating a uniform defect across the width of a coated conductor). The sample of the coated conductor was conduction-cooled to 30 K, and a magnetic field was applied (μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> up to 2 T) perpendicular to the wide face of the conductor to control its critical current. Transverse voltages in a multifilament coated conductor were measured to obtain the transverse currents among the filaments through the copper layer. Thermal runaway currents (operating currents above which thermal runaway initiates) of the monofilament sample and those of the multifilament sample with additional Joule loss due to the transverse currents were determined and compared to study the effect of the transverse currents on the initiation of thermal runaway in the multifilament coated conductor. Experiments on the protection against thermal runaway were conducted. When a normal voltage (over a preset threshold) was detected, the supplied current would be decreased exponentially. The thresholds for protecting monofilament and multifilament coated conductors from degradation after thermal runaway were compared.

Recording brain responses to TMS of primary motor cortex by EEG – utility of an optimized sham procedure

IntroductionElectroencephalography (EEG) is increasingly used to investigate brain responses to transcranial magnetic stimulation (TMS). A relevant issue is that TMS is associated with considerable auditory and somatosensory stimulation, causing peripherally evoked potentials (PEPs) in the EEG, which contaminate the direct cortical responses to TMS (TEPs). All previous attempts to control for PEPs suffer from significant limitations. Objective/HypothesisTo design an optimized sham procedure to control all sensory input generated by subthreshold real TMS targeting the hand area of the primary motor cortex (M1), enabling reliable separation of TEPs from PEPs. MethodsIn 23 healthy (16 female) subjects, we recorded EEG activity evoked by an optimized sham TMS condition which masks and matches auditory and somatosensory co-stimulation during the real TMS condition: auditory control was achieved by noise masking and by using a second TMS coil that was placed on top of the real TMS coil and produced a calibrated sound pressure level. Somatosensory control was obtained by electric stimulation (ES) of the scalp with intensities sufficient to saturate somatosensory input. ES was applied in both the sham and real TMS conditions. Perception of auditory and somatosensory inputs in the sham and real TMS conditions were compared by psychophysical testing. Transcranially evoked EEG signal changes were identified by subtraction of EEG activity in the sham condition from EEG activity in the real TMS condition. ResultsPerception of auditory and somatosensory inputs in the sham vs. real TMS conditions was comparable. Both sham and real TMS evoked a series of similar EEG signal deflections and induced broadband power increase in oscillatory activity. Notably, the present procedure revealed EEG potentials and a transient increase in beta band power at the site of stimulation that were only present in the real TMS condition. DiscussionThe results validate the effectiveness of our optimized sham approach. Despite the presence of typical responses attributable to sensory input, the procedure provided evidence for direct cortical activation by subthreshold TMS of M1. The findings are relevant for future TMS-EEG experiments that aim at measuring regional brain target engagement controlled by an optimized sham procedure.

A Method for Comparing the Metrological Properties of Eddy Current Probes

This article describes a method for comparing the metrological properties of air-cored and solid-cored coils designed as eddy current probes. The approach suggested in this article assumes that a pair of equivalent parameters of an ideal filamentary coil can be assigned to any contact coil so that the impedance variations in both coils are identical. These two parameters include the coil radius and its distance from the surface of a test piece. The experiments performed demonstrate that for equivalent parameters defined in such a way, impedance variations in a real and filamentary coil are the same for a broad frequency range of excitation current and conductivity of the material being tested. Therefore, comparisons between parameters of eddy current probes such as sensitivity, depth of penetration, or inspection coverage can be made with the use of a simple model of an ideal filamentary coil defined by only two parameters. The solution proposed in this article substantially simplifies the calibration process of the measuring instrument, the adjustment and optimization of parameters for newly designed probes, and the development of efficient and reliable mechanisms to eliminate undesired effects (e.g., lift-off).

DNS and LES of spark ignition with an automotive coil

The cycle to cycle combustion variability which is observed in spark-ignition engines is often caused by fluctuations of the early flame development. LES can be exploited for a better understanding and mastering of their origins. For that purpose appropriate models taking into account energy deposition, mixture ignition and transition to propagation are necessary requirements. This paper presents first DNS and LES of spark ignition with a real automotive coil and simplified pin-pin electrodes. The electrical circuit characteristics are provided by ISSIM while the energy deposition is modelled by Lagrangian particles. The ignition model is first evaluated in terms of initial spark radius on a pin-pin ignition experiment in pure air performed at CORIA and EM2C laboratories, showing that it pilots the radius of the torus formed by the initial shock wave. DNS of a quiescent lean propane/air mixture are then performed with this ignition system and a two-step mechanism. The impact of the modelled transferred energy during glow phase as well as the initial arc radius on the minimum ignition energy (MIE) are examined and compared to experimental values. Replacing the two-step chemistry by an analytically reduced mechanism leads to similar MIE but shows a different ignition kernel shape. Finally, LES of turbulent ignition using a Lagrangian arc model show a realistic prediction of the arc shape and its important role on the energy transfer location and thus on the flame kernel shape.

HIGH FREQUENCY DEEP REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION (dTMS) OF MEDIAL PREFRONTAL AND ANTERIOR CINGULATE CORTICES IN PATIENTS WITH OCD: A DOUBLE-BLIND, PLACEBO CONTROLLED, PERSPECTIVE MULTI-CENTER STUDY

Introduction Obsessive compulsive disorder (OCD) is a disabling disease with an annual prevalence of 1.2%. Currently approved medications only result in a reduction of symptoms for 40-60% of patients leaving most patients significantly affected. Symptom severity is correlated to the degree of hyperconnectivity in the cortico-stiriato-thalamic circuit and increased glucose metabolism in the anterior cingulate cortex during symptom provocation and at rest. Methods Ninety-four OCD patients who met inclusion/exclusion criteria (age 22-68, YBOCS≥20 despite SSRI treatment and/or CBT, stable on medications or therapy for at least two months) were randomized to receive active or sham treatment for twenty-nine sessions over six weeks. Deep transcranial magnetic stimulation(dTMS) was applied over the medial prefrontal(mPFC) and anterior cingulate cortices(ACC) using the H7 dTMS coil. Once the coil was in the treatment position, the patient’s symptoms were provoked using an individualized script tailored to the patient’s obsessions and compulsions. Subsequently, dTMS was administered for eighteen minutes at 100% resting motor threshold of the foot, 20HZ pulse frequency, in 2 second trains, with a 20 second inter-train interval totaling 2000 pulses. The sham coil was designed to have the same sound, scalp and facial sensation of the real coil without stimulating the brain directly. Results The mean age of the subjects was 38.7 (±11.75), 58.7%male, 78.8% Caucasian, mean age of onset was 13, 98% had failed medications approved for OCD and 68.7% had failed CBT. At the end of week 6 (the primary endpoint) the YBOCS decreased by 5.7 points (95% CI: [3.3;8.2]) in the dTMS arm and by 3.0 points (95% CI: [0.7;5.4]) in the control arm (p-value: 0.0157). Response (≥30% decrease/20% decrease in the YBOCS) rates were dTMS 38.10% in the dTMS arm and 11.11% in the sham arm (p-value:0.0033). Partial response rates were (≥20% decrease in the YBOCS) 54.76 in the dTMS arm and 26.67% in the sham arm (p-value: 0.0076). At week 10 (follow up) the YBOCS decreased by 6.2 points (95% CI: [3.6;8.7]) in the dTMS arm and by 3.8 points (95% CI: [1.4;6.2]) in the control arm (p-value: 0.0459). There were no serious adverse events related to the treatment. The most frequent adverse event, headache, did not differ in frequency between the two arms. Conclusions High frequency dTMS of the ACC was found to be an effective treatment for OCD. This approach is an additional intervention in the toolbox for treating OCD.

Idealized Coil Cross Sections With Minimized Conductor Area for High Field Dipoles

In the design of superconducting accelerator magnets, the shape of the coil cross section is mainly driven by the minimization of the conductor volume, constrained by requirements on the central magnetic field and its homogeneity. Such optimizations commonly assume either a Block or Cosine Theta coil type, which is then filled with (predetermined) rectangular or key-stoned Rutherford cables. By optimizing the positions, angles, and the number of turns, the field quality requirements and cost minimization are achieved. However, this leaves to wonder what the optimal coil geometry looks like, when such practical constraints are not present. Although such a coil cross section has always been presented as the intersection between two ellipses, this method results in a noncircular aperture and is thus not fully representative of a realistic coil. This paper introduces a method in which organically shaped (nongraded) dipole coil layouts are optimized without any assumptions on the conductor. The resulting layouts are presented as a function of overall current density, aperture size, and required magnetic field (inside the aperture). The layouts presented should be viewed as an ultimate limit of what can be achieved, for comparison with real coil layouts, and as an initial guide for finding an optimal cross section for a realistic magnet.

Analysis of the transient state in a parallel circuit of the class RLβCα

The paper presents the results of the conducted analysis of transient states in a parallel circuit of the class RLβCα, supplied by an ideal current source. The considered circuit consists of a real coil Lβ and a (super)capacitor Cα, modeled as fractional-order elements. The paper proposes a method for determining the current and voltage waveforms, which uses the decomposition of rational functions into partial fractions and inverse Laplace method. By using this method, transient waveforms occurring in the system for any kind of current excitation can be determined. Two cases of the problem solutions have been considered in the paper, for real and complex poles of the rational functions, which result from the analysis of the main fractional-order differential equation, describing the considered circuit. Analytical relations describing transient state waveforms in the system have been determined for different types of current excitations: constant, monoharmonic, polyharmonic and arbitrary being an element of a Hilbert space. The obtained results have been illustrated by an examplary case of a parallel circuit of the class RLβCα. The paper is a continuation of previous studies concerning transient-state analysis in circuits with elements modeled as fractional-order (Jakubowska and Walczak 2015, 2016).

Design and Comparison of a 1-MW/5-s HTS SMES With Toroidal and Solenoidal Geometry

The design of a HTS SMES coil with solenoidal and toroidal geometry is carried out based on a commercially available 2G HTS conductor. A SMES system of practical interest (1 MW / 5 s) is considered. The comparison between ideal toroidal and solenoidal geometry is first discussed and the criteria used for choosing the geometrical parameters of the coils' bore are explained. The design of the real coil is then carried out and the final amount of conductor needed is compared. A preliminary comparison of the two coils in terms of AC loss during one charge discharge cycle is also discussed.

An Analytic Analysis of the Multi-Degree-of-Freedom Actuator

This paper discusses the analysis and simulation method and the test method for a two-degree-of-freedom (2-DOF) actuator torque. The previous studies on the analysis of 2-DOF motor’s tilting torque were carried out only by finite element method (FEM), not by analytic method. This paper describes the operating principles of and the processes of inducing a tilting torque and a holding torque both of which exist only in special purpose electric machines. This allowed us to establish a design process. By overcoming the limits of the 3-D FEM, this paper introduced the 2-D model analysis by considering a real coil shape. Finally, this paper manufactured and tested the 2-DOF actuator to verify the introduced analytic analysis method.

Magnetic Design Optimization of a 150 mm Aperture &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$ \hbox{Nb}_{3}\hbox{Sn}$&lt;/tex&gt;&lt;/formula&gt; Low-Beta Quadrupole for the HiLumi LHC

As part of the Large Hadron Collider Luminosity upgrade (HiLumi) program, the US LARP collaboration and CERN are working together to design and build a 150 mm aperture <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{Nb}_{3} \hbox{Sn}$</tex></formula> quadrupole magnet that aims at providing a nominal gradient of 140 T/m. In this paper we describe the optimization process yielding the selected 2D coil cross-section and the 3D coil ends design. For the 2D optimization a sector-coil model that allows fast computation of field harmonics is used to identify, among a large number of cases, those cross-sections that provide an acceptable field quality. A more detailed analysis of these solutions is then performed and it led to the selection of an optimized cross-section from which a real coil is built by approximating sectors with blocks of cable. A 3D design of the coil ends is then realized with the Roxie software. Optimization constraints are set on the integrated multipoles, the peak field, and the coil head length.

Repetitive transcranial magnetic stimulation reduces cigarette consumption in schizophrenia patients

High-frequency repetitive transcranial magnetic stimulation (rTMS) over the left dorsolateral prefrontal cortex (DLPFC) seemed to decrease tobacco consumption and craving in nicotine-dependent people without psychiatric disorder or otherwise healthy people. Even if the prevalence of cigarette smoking in schizophrenia patients is high and estimated to be between 45% and 88%, this technique has not been systematically studied in this indication in schizophrenia yet. The aim of this study was to test the ability of high-frequency (10Hz) rTMS over the left DLPFC to decrease cigarette consumption in schizophrenia patients. The study included 35 male schizophrenia patients on stable antipsychotic medication. The patients were divided into two groups: the first (18 patients) were actively stimulated and the second (17 patients) underwent sham (placebo) stimulation. The sham rTMS was administered using a purpose-built sham coil that was identical in appearance to the real coil and made the same noise but did not deliver a substantial stimulus. The rTMS was administered at the stimulation parameters: location (left dorsolateral prefrontal cortex: DLPFC), intensity of magnetic stimulation in % of motor threshold (110%), stimulation frequency (10Hz), number of trains (20), single train duration (10s), inter-train interval (30s), and total number of stimulation sessions (21). In each stimulation session, 2000TMSpulses were given, with a total of 42,000pulses per treatment course. Patients noted the number of cigarettes smoked in the 7days before treatment, during the whole stimulation treatment (21days), and again for a 7-day period after treatment. Cigarette consumption was statistically significantly lower in the actively stimulated patients than in the sham rTMS group as early as the first week of stimulation. No statistically relevant correlations were found in the changes of ongoing negative or depressive schizophrenia symptoms and the number of cigarettes smoked. High-frequency rTMS over the left DLPFC has the ability to decrease the number of cigarettes smoked in schizophrenia patients.

Phase reconstruction from multiple coil data using a virtual reference coil

This study develops a method to obtain optimal estimates of absolute magnetization phase from multiple-coil MRI data. The element-specific phases of a multi-element receiver coil array are accounted for by using the phase of a real or virtual reference coil that is sensitive over the entire imaged volume. The virtual-reference coil is generated as a weighted combination of measurements from all receiver coils. The phase-corrected multiple coil complex images are combined using the inverse covariance matrix. These methods are tested on images of an agar phantom, an in vivo breast, and an anesthetized rabbit obtained using combinations of four, nine, and three receiver channels, respectively. The four- and three-channel acquisitions require formation of a virtual-reference receiver coil while one channel of the nine-channel receive array has a sensitivity profile covering the entire imaged volume. Referencing to a real or virtual coil gives receiver phases that are essentially identical except for the individual receiver channel noise. The resulting combined images, which account for receiver channel noise covariance, show the expected reduction in phase variance. The proposed virtual reference coil method determines a phase distribution for each coil from which an optimal phase map can be obtained.

R3B-Glad Magnet Cold Mass Manufacture: Coils and Casings Fabrication and Integration

The R3B-Glad magnet is part of a large acceptance spectrometer devoted to the physics of exotic nuclei, under construction at CEA Saclay (France) for the present GSI and the future Fair facilities (Darmstadt, Germany). In this paper is presented the fabrication of the cold mass (22 t), divided into three batches (coil manufacture, machining of coil casings, and integration of the coils inside their casings). The work began in January 2009 and ended in December 2010. A real size prototype coil, was developed to validate the winding process, with double pancakes assembled in a stacking tool, and the procedure for impregnating coils, inserted into a mold. After impregnation of the prototype and the first coil, a failing (short circuit between turns) was detected in both coils by electrical testing. The repair of various defects has been a success. Insulation reinforcements were performed on the following coils to avoid any further electrical default. The whole set of coils was wound and impregnated in 2010 (6 coils, about 3 meter long each). The casings are made of aluminum alloy 5083 (with the exception of a few pins, screws and bolts made of stainless steel) and machined from single blocks without welding. All parts were machined in two stages. The first step was a premachining to perform a blank assembly of the whole cold mass (performed in February 2010). The final machining was performed according to the actual dimensions of the manufactured coils, in order to get a perfect fit of the coils within their casings. The integration of the coils inside their casings (including shims setting, adjusting of pushing systems, bonding of drains and thermal sensors) occurred in autumn 2010. The set of coils in their casings was delivered to Saclay in December 2010.

Resonance Characteristics and Maximum Turn Voltage of JT-60SA EF Coil

The withstand voltage of the turn insulation is one of the most essential issues for the superconducting magnet system. There is a possibility that the actual differential voltage between each turns, called turn voltage in this paper, is larger than the maximum turn voltage under the ideal condition because of the voltage fluctuations of the power supply and the inhomogeneous voltage distribution in the magnet induced by the resonance phenomenon. The actual turn voltage was evaluated by the voltage measurements and the circuit simulation. The actual voltage of the large power supply, JT-60U power supply, was measured. The results indicated that the actual maximum voltage increase the 20% from rated voltage of the power supply. The margin of the insulation voltage is generally much larger than 20%. This amplitude of the voltage fluctuations is permissible for the design of the turn insulation. The resonance characteristic test was performed using the copper dummy pancake. The test results suggested that the resonance frequency of the EF4 pancake was about 56 kHz. The resonance characteristics of the real coil was also evaluated by the numerical method based on the lumped parameter circuit model. The resonance frequencies of the EF4 coil were calculated as 180 kHz, 300 kHz and the several higher frequencies. The main frequency component of the power supply is less than 5 kHz. The influence of the resonance phenomenon on the maximum turn voltage is negligible small.

Detecting Cooling Coil Fouling Automatically—Part 2: Results Using a Multilayer Perceptron

A new concept to automatically detect cooling coil fouling is introduced in a companion paper (Veronica 2010). The concept maintains a data-driven dynamic model of the cooling coil on-line with coil instruments, so all steady and transient coil behavior is assimilated. The fouling surveillance is to periodically apply a specific transient sequence (the query) to this model off-line as a surrogate for applying such a test to the real coil. A query sum, calculated from the transient response of the model to a query, is used to detect changes in the real coil, to discern fouling from other faults such as instrument drift, and to further discern water-side from air-side fouling. A crucial element to viability of the concept is that the data-driven coil model respond to queries dynamically and recursively, with sufficient stability and accuracy so that fouling can be discerned. Yet, the model should be of reasonably simple architecture, permitting a plausible embedded implementation. Based on trials using simulator data, a relatively simple, three-node, multilayered perceptron demonstrates sufficient accuracy and stability so that the concept can be regarded as viable and as warranting further development. Also presented are the factors found to be critical for dynamically employing a data-driven model of any architecture to detect process faults.

Detecting Cooling Coil Fouling Automatically—Part 1: A Novel Concept

Fouling of surfaces within the heat exchangers of heating, ventilating, and air-conditioning (HVAC) systems of buildings is an equipment fault that wastes appreciable amounts of energy; however, it escapes detection under current building automation technology. A novel concept is introduced to automatically detect this fouling on water-side and air-side surfaces of water-cooled HVAC air coils. The concept incorporates a model-driven component contributing a table of human expert information and an embedded data-driven component assimilating real-time data sampled from HVAC plant instrumentation. Supervisory programming (the “agent”) conducts real-time surveillance for coil fouling using the data-driven component, which is a model replicating the current dynamic thermal behavior of the coil. The surveillance is a specific characterizing transient (a “query”) exercised periodically on the data-driven dynamic coil model as a surrogate for exciting the real coil. When a query returns a suspect result, the agent determines if coil fouling or some other change caused that result by using the tabulated expert information. The concept makes use of all data sampled from the plant, reflecting transient and steady behavior. Fouling can be discerned from other developments, such as instrument drift, and the agent can distinguish air-side fouling from water-side fouling, estimate the severity of fouling, and estimate an uncertainty for its classification. The values tabulated describe three-dimensional surfaces characterizing the varied impact fouling generically has on coil thermal effectiveness when considered over the state space of coil operation. Categorical use of that information by the concept is justified by analysis in the effectiveness-NTU state plane. A companion paper (Veronica 2011) gives results of exercising a crucial task within the concept on simulated data by using one form of a dynamic data-driven model; a multilayer perceptron.