Search Coil Research Articles

Photoelectric inequivalence characteristics of an electric substitution radiative heat flux meter

Photoelectric inequivalence characteristics of an electric substitution radiative heat flux meter

A Simple Search Coil Based on Motor Winding Strands for Rotor Position Estimation

A Simple Search Coil Based on Motor Winding Strands for Rotor Position Estimation

Saliency-Based Rotor Spatial Position Displacement Self-Sensing for Self-Bearing Machines.

Self-bearing machines do not contain physical bearings but magnetic bearings. Both rotor rotary and spatial positions displacement are required in these types of machines to control the rotor position while it is levitating. Self-bearing machines often use external sensors for x (horizontal) and y (vertical) spatial position measurement, which will result in additional cost, volume, complexity, and number of parts susceptible to failure. To overcome these issues, this paper proposes a xy-position estimation self-sensing technique based on both main- and cross-inductance variation. The proposed method estimates x and y position based on inductive saliency between two sets of three-phase coils. The proposed idea is applied on a combined winding self-bearing machine which does not require additional suspension force winding. No additional search coil placement for xy-position estimation is required. Therefore, the proposed algorithm can result in a compact size self-bearing machine that does not require external sensors for xy-position measurement and suspension force winding.

Estimation of Thermal Radiation in Bed Mattresses

The population density of cities has been increasing with time and the development of industry. Building fires in large cities with high population density cause extensive human and property damage. To prevent such damage, the characteristics of flames such as the thermal radiation and intensity of the fire source must be considered when designing building structures. However, the consideration of these factors is practically inadequate. Accordingly, in this study, when a mattress was ignited in an open environment at a different installation height (0–515 mm), the measurements from a heat flux meter and the calculated thermal radiation were compared, and a comparative analysis was conducted using the existing prediction formulas by researchers described in ISO 24678-7. We examined the fire risk of mattresses according to the mattress installation height. As a result, the fire risk of the mattress was confirmed according to the mattress installation height; upon comparing the experimental and calculated values for radiant heat, it was found to be necessary to estimate the radiant heat using a calculation method that applies the configuration factor differently depending on the change in the flame shape. In addition, as a result of substituting the experimental value into the calculation method of ISO 24678-7 (a method for estimating the radiant heat of liquid combustibles), the experimental value and the calculated value were found to be significantly different. Therefore, similar to ISO 24678-7 for the radiation heat estimation method for “liquid combustibles”, an international standard for establishing the radiation heat estimation method for “solid combustible materials” as a standard was also required for a reasonable analysis of the fire safety phenomenon of solid materials, such as bed mattresses.

Characterization of commercial thermoelectric modules for precision heat flux measurement.

In this article, we present a cost-effective approach to the precision measurement of heat flux using commercial thermoelectric modules (TEMs). Two different methods of measuring heat flux with TEMs are investigated, namely, passive mode based on the Seebeck effect and active mode based on the Peltier effect. For both modes, a TEM as a heat flux meter is calibrated to show a linear relation between the voltage across the TEM and the heat flux from 0 to ∼450Wm-2. While both modes exhibit sufficiently high sensitivities suitable for low heat flux measurement, active mode is shown to be ∼7 times more sensitive than passive mode. From the speculation on the origin of the measurement uncertainty, we propose a dual TEM scheme by operating the top TEM in passive mode while its bottom temperature maintains constant by the feedback-controlled bottom TEM. The dual TEM scheme can suppress the sensitivity uncertainty up to 3 times when compared to the single-TEM passive mode by stabilizing the bottom temperature. The response time of a 15 × 15mm2 TEM is measured to be 8.9 ± 1.0s for heating and 10.8 ± 0.7s for cooling, which is slower than commercial heat flux meters but still fast enough to measure heat flux with a time resolution on the order of 10s. We believe that the obtained results can facilitate the use of a commercial TEM for heat flux measurement in various thermal experiments.

Development and validation of a low magnetic permeability measurement setup

Measurement of relative permeability has a significant role in deciding the suitability of magnetic material for various industrial applications. Several developments and modifications have been made that can directly or indirectly measure the permeability of such materials. However, these developments suffer from various limitations, such as low accuracy, poor resolution, and high cost of measurement. In this work, a new measurement setup has been developed to precisely measure relative permeability in the range of 1-2. The setup has been designed based on the flux metric (solenoid) method in accordance with ASTM A 342 and EN 60404-15. A comparative analysis has been performed for known materials using different flux meters to verify the performance of the measuring coil. The developed setup was further validated against the magnetic moment method, i.e., vibrating sample magnetometer (VSM), regarding the permeability measurement of these materials. The results depicted a close agreement between the output of the developed setup and VSM data. The developed system claims a relative error of less than 1% with respect to VSM in measuring the permeability of materials. Measurement uncertainty for the developed system was also determined. Such an accurate and low-cost measurement setup can become a possible solution for the permeability measurement of feebly magnetic materials.

A novel online method for locating fault coil in direct‐drive permanent magnet synchronous motor with inter‐turn short‐circuit fault using search coil array

This study presents a fault coil localisation approach for a direct-drive permanent magnet synchronous motor (DDPMSM) with inter-turn short-circuit fault (ISF) using the search coil (SC) array. The SCs are wound around specific stator tooth of DDPMSM through the proposed SC array arrangement principle, which reduces the invasiveness of the fault coil localisation method. The SCs are classified as several search coil groups (SCGs), the differential between SC back electromotive forces (EMFs) in the same SCGs (δ1) and SC residual back EMF (δ2) are used as fault indicators for ISF localisation. The peak values extracted from δ1 and δ2 are the basis for diagnosing ISF. Hence, the proposed approach does not need a complicated signal processing algorithm, and it is less complex. First, the SC back EMF analytical model is developed to investigate the mapping relationship between the back EMF of each SC and fault coil location. Second, fault coil localisation indicators for ISF are analysed based on the proposed analytical model, and the exact ISF localisation approach is presented. Finally, two basic installation units and the arrangement principle of SC array in DDPMSM are proposed. Simulation and experimental results justify the effectiveness of the selected fault indicators and the feasibility of the proposed SC array for diagnosing ISF.

Water flux profiling in fractured rock boreholes with an In-Well Point Velocity Probe (IWPVP)

• First field measurements with the fracture adapted IWPVP reached 38 m below ground surface. • Depth profile of water fluxes compares well with PFM, ORP, and FLUTe liner profiles. • Demonstrated calibration of probe measurements with acoustic borehole televiewer data. • IWPVP shown to be a simple, cost-effective tool for measuring flow in fractures. Flow in a fractured rock aquifer beneath the Edwards Air Force Base in California was characterized by depth profiling two wells with In-Well Point Velocity Probes (IWPVPs). The probes, which were originally designed for use in porous media wells, were optimized for use in fractured rock wells and to meet several challenges including: sampling depths up to 38 m; high background site-water salinity; and variable well construction (screened vs open borehole, and well diameters of 7.62 cm and 15.8 cm). The IWPVP measures water flux inside the probe (internal flux), which is converted to fluxes in the aquifer through calibration. At this site, the internal fluxes ranged from 3 to 53 m/d. The channeled internal design of the probe inherently provides information about general flow directions and allows further interpretation of specific flow direction within ±15°, which at this site was generally consistent with the expected regional flow direction. Notably, a significant shift in the flow system was observed following a rain event (up to 180° shift in the flow direction). The IWPVP identified highly transmissive zones in the fractured rock, which were independently confirmed by passive flux meters and oxidation-reduction potential sensors. Transmissivity profiles determined during a FLUTe (Flexible Liner Underground Technologies™) liner deployment also showed similarities in the depths of potentially high flow rates, particularly in the shallower portion of the well (<20 m). With additional information on fracture apertures provided by an acoustic televiewer, the internal fluxes were converted to water fluxes in the observed fractures, indicating seepage velocities in the rock aquifer between 3.7 m/d and 22.4 m/d.

Scale‐Dependent Kurtosis of Magnetic Field Fluctuations in the Solar Wind: A Multi‐Scale Study With Cluster 2003–2015

AbstractDuring the lifetime of the Cluster mission, the inter‐spacecraft distances in the solar wind have changed from the large, fluid, scales (∼104 km), down to the scales of protons (∼102 km). As part of the guest investigator campaign, the mission achieved a formation where a pair of spacecraft were separated by ∼7 km. The small distances and the exceptional sensitivity of the search coil magnetometer provide an excellent data set for studying solar wind turbulence at electron scales. In this study, we investigate the intermittency of the magnetic field fluctuations in the slow solar wind. Using 20 time intervals with different constellation orientations of Cluster we cover spatial scales between 7 and 104 km. We compare time‐lagged increments from a single spacecraft with spatially lagged increments using multiple spacecraft. As the turbulent cascade proceeds to smaller scales in the inertial range, the deviation from Gaussian statistics is observed to increase in both temporal and spatial increments in the components transverse to the mean field direction. At ion scales, there is a maximum of kurtosis, and at sub‐ion scales, the fluctuations are only weakly non‐Gaussian. In the compressive component the deviation from Gaussian statistics is variable: it may increase throughout the inertial and sub‐ion ranges, but also, it may have a maximum at magnetohydrodynamic scales associated with large scale magnetic holes. The observations show differences in kurtosis of time and space increments when the spacecraft pairs are transverse to the flow, indicating its spatial anisotropy.

Fire Properties of Hybrid Composites

Thermal conductivity of a components subjected to high temperature is an important property to be considered in a materials to be used in automobile and aerospace fire designated zones; likewise, it is availability, cost, stiffness, resistant to corrosion, and its strength. The main aim of the study is to investigate the fire behavioural properties of fibre metal laminates (FML) composite of a metal, synthetic, natural and polymer matrix. The composites were fabricated in a mould using hand lay-up method and allow to cured before test.. The fire property test was carried out using the standard properties test equipment as ISO 2685 propane burner thermocouples and heat flux meter. The result of the properties test shows a remarkable increase in the properties of only natural fibre metal laminate composites, with a slight decrease in the properties of pure synthetic fibre metal laminates. Flax composite has a high percentage of 21.43% of thermal conductivity and withstand the flame temperature for 15 minutes using an ISO 2685 standard while kenaf composite fail at 10 minutes 30 seconds, Conclusively, the composites can be used as the component in fire designated zones of automotive, aerospace and other machines.

A Novel Design Nomogram for Optimization of Micro Search Coil Magnetometer for Energy Monitoring in Smart Buildings.

In this paper, a new analytical method to achieve the maximum signal-to-noise ratio (SNR) of a micro search coil magnetometer (µSCM) is presented. A planar spiral inductor was utilized to miniaturize conventional bulky search coil magnetometers. First, dimensional analysis was applied to identify three dimensionless parameters for the µSCM’s key performance indices (sensitivity (Se), noise, and SNR). The effect of the parameters on the µSCM’s performance was carefully investigated, and a novel 4D nomogram was developed. Furthermore, an SNR analysis considering noise sources of a low-noise amplifier was performed. By combining the results from the nomogram and the effect of the noise sources from the amplifier circuit, optimum values for the dimensionless parameters were calculated. According to the calculation results, the dominant noise source varied with an increase in the track width ratio to the outer diameter. Seven different samples were fabricated by a single-mask lithography process. The sensitivity of 1612 mV/mT was demonstrated at a 50 Hz input magnetic field, which was better than the previous µSCM (Se = 6.5 mV/mT) by more than 2 orders of magnitude. Finally, one of the fabricated µSCMs was employed to measure the online power consumption of a personal computer while different types of software were running.

Performance Characterisation of a New Plaster Composite Lightened with End-of-Life Tyres' Recycled Materials for False Ceiling Plates.

Plaster is one of the most used and studied materials in the building process. This paper shows the result of the characterisation of a new plaster-based material enlightened and reinforced with polymers and end-of-life tyres’ recycled materials. As far as end-of-life tyres are a common waste item, this paper offers new recycling possibilities, as well as significant improvements in new building materials. Mechanical, thermal conductivity, sound absorption, fire reaction and environmental impact are studied and analysed. Three different end-of-life tyres’ recycled materials are used, two size rubber and textile fibres. A significant density reduction up to 17% was achieved mainly due to end-of-life materials lower density. Two thermal conductivity measurement methods, heat flux meter and guarded hot plate, were conducted and then compared. A 20% improvement with respect to the reference was achieved in those samples with textile fibre. The two methods’ measurements got a 1% difference in all samples analysed except textile fibre. Thus, this allowed to validate these methods and assure these measurements. Sound absorption was also measured. These materials reached α = 0.32 in high frequencies. Performance in low frequencies were lower. Fire tests led to no ignition results and no fire propagation. Finally, a basic global warming potential impact study based on environmental product declaration (EPD) is conducted. The most relevant result of this study is the potential 20–34% reduction of CO2 emissions with the elaboration of these composites.

Quasi‐Periodic Whistler Mode Emission in the Plasmasphere as Observed by the DSX Spacecraft

AbstractWe describe the quasi‐periodic (QP) whistler‐mode emissions found in the plasmasphere as detected by electric and magnetic instrumentation onboard the Demonstration and Science Experiments (DSX) spacecraft in medium Earth orbit. Over the course of the nearly 2‐year mission, at least 45 episodes of whistler mode QP emissions were detected by the Broad Band Receiver (BBR) onboard DSX. Episodes of QP emissions were identified by discrete events having a clear unambiguous periodic nature as detected by both the electric antennae and search coil magnetic sensors in the BBR survey data at 30 s temporal resolution. Most of the QP episodes occurred in a frequency range between 1 and 4 kHz, in a band previously identified by Van Allen Probes and Cluster investigators. However, episodes were also detected by DSX at higher frequencies ‐ events in these episodes extending all the way to 15 kHz. We present our findings on these unusual high frequency events in the presentation herein. Specifically, these high frequency QP episodes tended to be observed near dawn/dusk when the spacecraft was at relatively high magnetic latitudes and on magnetic L‐shells between 3 and 5. Another unusual feature of these episodes is that individual up‐drifting events making up the episode were found to sometimes occur concurrently in time: The high frequency portion of one up‐drifting “polliwog‐shaped” event overlapped in time with the low frequency portion of the subsequent event. This behavior of the QP emissions has not been previously emphasized and we consider how this temporal concurrence relates to the source processes.

The flame mitigation effect of N2 and CO2 on the hydrogen jet fire

Hydrogen has attracted much attention from governments and enterprises around the world due to its zero pollution and recycling use. However, it may bring safety problems such as hydrogen jet fire due to its wide flammability range and low ignition energy. Therefore, the methods of preventing hydrogen jet fire need to be explored urgently. In order to investigate the effect of gaseous fire extinguishing agent on the hydrogen jet fire, a series of experiments were carried out to study the flame behaviors under the effects of nitrogen and carbon dioxide jets. The fire extinguishing agents were released through a jet nozzle with diameter of 3 mm at the pressure of 11 atm. The flame length, thermal radiant flux and total heat flux were analyzed. The results show that the reduction ratio of vertical flame length increases with the decrease of the installation height of the extinguishing agent nozzle. It indicates that when the fire extinguishing agent is injected at the root of hydrogen jet flame, the fire may be extinguished. Due to the reduction of flame size, the thermal radiant flux received by the radiometer decreases, which corresponds to the reduction of flame radiation fraction. The total heat flux received in the downstream region of deflected flame is determined by the joint action of thermal radiation and convection. The convective heat transfer of high-temperature gas may cause the value measured by the heat flux meter on the flow path of the deflected flame to increase. Besides, the extinguishing limit for hydrogen jet flame under the effects of nitrogen and carbon dioxide jets are analyzed.

Airgap Search Coil Based Identification of PM Synchronous Motor Defects

Online detection of rotor and load faults in permanent magnet synchronous motors (PMSM) based on spectrum analysis of current or vibration is not capable of identifying the root cause of the fault, since all faults produce identical fault signatures. The sensitivity of fault detection also depends on the motor and controller design making fault detection unreliable. In addition, operation under variable frequency and load limits the effectiveness of spectrum analysis based methods. In this article, airgap flux monitoring is investigated as an alternative for providing reliable identification of rotor and load faults in PMSMs. Based on the analysis of airgap flux under partial and uniform demagnetization, dynamic eccentricity, and load unbalance, an airgap search coil voltage based method for detection and classification of the faults is proposed. The claims made in the article are verified through experimental testing on an IPMSM under emulated fault conditions along with a comparison to vibration and current spectra-based detection. It is shown that the proposed method provides reliable online identification of the faults for cases where conventional spectrum analysis based methods fail.

How Do Temperature Differences and Stable Thermal Conditions Affect the Heat Flux Meter (HFM) Measurements of Walls? Laboratory Experimental Analysis

In recent years, experimental tests related to building components through laboratory facilities have relatively matured. The techniques are based on one-dimensional heat transfer by creating a permanent temperature difference over a specimen to control heat fluxes. The three main methods are the Guarded Hot Box (GHB) method, the Calibrated Hot Box (CHB) method, and the Heat-Flow Meter method (HFM). The HFM method is the most widely applied technique for measuring on-site U-values of building components and several scientific works stressed the need for high temperature differences between the environments, suggesting 10 °C or 15 °C. However, temperature stability and high temperature gradients are difficult to obtain, especially for Mediterranean climatic conditions. Starting from this, an experimental study was conducted through a GHB apparatus, setting temperature differences from 2 °C to 20 °C between the hot and cold chambers. Heat flow measurements were performed to compute the thermal conductance of a specimen characterized by a known stratigraphy, thus highlighting the effect of the low thermal gradient on data acquired by the heat flow sensor. It was found that, even for low temperature differences (2 °C) maintained by ensuring stable thermal conditions, the experimental results are comparable with those obtained for higher and usual temperature differences (20 °C).

The Confirmation of Thermal Boundary Parameters in an Oxygen Kerosene Fuel-Rich Rocket Engine

The thermal environment is an important factor in the design of liquid rockets. In this paper, theoretical analysis, numerical simulation and experimental testing are conducted to study the boundary thermal characteristics of a GOX/kerosene liquid rocket motor with a total flow rate of 120 g/s and an oxygen-fuel ratio of 1:1. We measured the axial temperature in different positions in the combustor using thermocouples and the heat flux using a flux meter. We found that the heat flux at 182 mm increases by 6.8% when a carbon deposit exists. For the theoretical results, after correcting the thermal conductivity by the volume fraction of carbon deposition, the theoretical heat flux (1.11 MW/m2, using the corrected thermal conductivity) and the numerical result (0.89 MW/m2, considering the injectors) are similar to the experimental value (0.937 MW/m2). This study validates the accuracy of theoretical and simulation calculation in this case, and provides verification data for future numerical calculation, as well as data for setting gas temperature at the wall in the simulation of the gas phase.

Evaluation of the energy storage capacity of Phase Change Material cement-lime mortars by using heat flux meters and ultrasonic pulse transmission

Materials with high energy storage capacity can enhance energy efficiency of buildings further than thermal insulation alone. The use of microencapsulated paraffin wax Phase Change Materials (PCM) in cement-lime mortars with cellulose fibres and lightweight aggregates (LWA) is a promising solution for this purpose. In this study, experimental techniques as flux heat meters and ultrasonic pulse transmission are used to evaluate the thermal performance and energy storage capacity of five cement-lime mortars with 20% of PCM, cellulose fibres and LWA (perlite) under different thermal conditions. A climatic chamber was used to simulate heating and cooling on one side of a sample plate of each mortar type, while the other side remained at lab conditions. Sample plates were instrumented with temperature-humidity sensors, heat flux meter plates and Ultrasonic (US) pulse transducers. US attenuation coefficient was used to identify the phase change PCM from solid to liquid and vice versa, during heating and cooling. The Heat flux difference between both sides of the plates was also measured during heating and cooling cycles. The specific enthalpy (energy storage capacity) of the mortars was calculated for heating and cooling cycles. Mixtures with LWA and PCM showed the best thermal performance achieving larger heat storage capacity than mortars with fibres or the combination of both LWA and fibres.

First Results From the SCM Search‐Coil Magnetometer on Parker Solar Probe

AbstractParker Solar Probe is the first mission to probe in situ the innermost heliosphere, revealing an exceptionally dynamic and structured outer solar corona. Its payload includes a search‐coil magnetometer (SCM) that measures up to three components of the fluctuating magnetic field between 3 Hz and 1 MHz. After more than 3 years of operation, the SCM has revealed a multitude of different wave phenomena in the solar wind. Here we present an overview of some of the discoveries made so far. These include oblique and sunward propagating whistler waves that are important for their interaction with energetic electrons, the first observation of the magnetic signature associated with escaping electrons during dust impacts, the first observation of the magnetic field component for slow extraordinary wave modes during type III radio burst events, and more. This study focuses on the major observations to date, including a description of the instrument and lessons learned.

Coupling effects of hydrogen and Dy/Nb on magnetic properties of sintered NdFeB magnets

The magnetic-property changes in sintered NdFeB magnets with different content of Dy and Nb after electrochemical hydrogen charging (EHC) were investigated. The phases of Dy2Fe14B, NbFeB, and Fe2Nb are confirmed by energy-dispersive spectrometry (EDS) and selected area electron diffraction. The electron back-scatter diffraction (EBSD) and electrochemical test show that the amount of Nd-rich grain boundary phases as hydrogen diffusion channels and the concentration of hydrogen near the surface of the magnets increase with the addition of Dy and Nb. Before and after EHC, the surface roughness and magnetic properties were measured using a laser scanning confocal microscopy, pulsed field magnetometer and flux meter. The results revealed that the surface roughness of magnets increases, owing to the absorption of hydrogen. During EHC, the remanence (Br) remains unchanged, whereas the magnitudes of the coercivity, magnetic moment (Mt), and maximum energy density ((BH)max) decrease by different degrees because of the presence of Dy and Nb compounds. Hydrogen decreases the stability of the magnet in demagnetization field by reducing the critical energy required for magnetic moment rotation, nucleation of reverse domains, and expansion of domain walls, and the presence of Dy and Nb compounds exacerbates the stability.