Coil Losses Research Articles

Performance analysis of superconducting motors for electrical aircraft propulsion using electromagnetic–thermal coupling method

The aviation industry is focusing on the development of low-carbon emission technologies, with hydrogen-powered aviation hybrid technology being an important area of interest. Superconducting motors (SCMs) play a crucial role in these aviation hybrid systems due to their high power-to-weight (PTW) ratio. However, SCMs face challenges such as strong coupling of the electric field, magnetic field, and temperature field within the motor. Conventional electromagnetic–thermal coupling analysis methods are not suitable for SCMs, as they are slow to perform calculations that are also less accurate. This study proposes an electromagnetic-thermal coupling analysis model for SCMs, taking into account the constraints of critical current, critical magnetic field, and critical temperature of superconducting (SC) materials. The study analyzes the impact of the critical current of SC tapes, permanent magnet remanence, convection heat transfer coefficient between SC coils and cooling medium, AC loss reduction of SC coils, and motor speed on the ultimate power of SCMs. The results show that an optimal permanent magnet remanence can maximize the ultimate power, and the other parameters have been found to be positively correlated with the ultimate power of the SCM. To enhance the PTW ratio of SCMs, future research directions include increasing the critical current of SC materials, reducing the AC loss of SC coils, and improving the cooling effectiveness of SC coils.

Numerical Study of AC Loss in a Saddle Coil Carrying DC and Experiencing AC Field Utilizing T-A Formulation

Numerical Study of AC Loss in a Saddle Coil Carrying DC and Experiencing AC Field Utilizing <i>T-A</i> Formulation

Impact of coil envelope on the coupling coefficient in magnetic induction wireless power transmission systems

Abstract Research in the field of wireless energy transmission by magnetic induction has increased in recent years, due to the diversity of applications, such as medicine, electronics, and transport, that require this technology. Despite its maturity to date, this technology has struggled itself due to the short transmission distance and low coupling coefficient between the transmitting and receiving coils. These coils are usually protected by an envelope. However, the impact of the nature of the envelope on the coupling coefficient has not been studied. This work focuses on the impact of the nature of the coil protection envelope on the coupling coefficient. Three-dimensional flat spiral coils and the protective envelope are modeled and subjected to parametric analysis with variable air gaps and frequencies using ANSYS-Electronics Maxwell 2022 R1 software with the finite element method (FEM). Simulation results show that a coil protected by an insulating envelope has a higher coupling coefficient than a coil protected by a conducting material. Simulation in this work have also shown that the coupling coefficient decreases as operating frequencies increase. The ohmic losses in coils protected by an insulating envelope are greater than those in coils protected by a conductive material.

Magnetization Losses in HTS Coil With Different Winding Method

Magnetization Losses in HTS Coil With Different Winding Method

Abstract 448: Treatment Modalities and Outcomes Among Patients with &lt;3mm and ≥3mm Intracranial Aneurysms

Introduction Treatment of very small, ruptured, and symptomatic intracranial aneurysms (IA) remains challenging, despite advances in endovascular and surgical techniques. We summarized outcomes for very small (&lt;3mm) vs. larger (≥3mm) IA in patients who underwent treatment. Methods Prospectively collected data from adults who underwent treatment for an IA at the Stroke and Neurovascular Center of Central California between August 2018 and August 2022 were retrospectively reviewed. Demographics, medical history, aneurysm, and procedural characteristics were recorded. Coiling procedures used the Optima Coil (Balt USA). Flow diverters included Pipeline (Medtronic, Inc.), Surpass Evolve (Stryker) and Synergy (Boston Scientific). Outcomes were post‐procedure Raymond‐Roy Occlusion Classification (RROC), retreatment, intraoperative complications, vasospasm, and mortality. Mann‐Whitney U tests compared continuous and ordinal baseline characteristics. Fisher's exact test compared dichotomous baseline variables and safety outcomes. Ordinal regressions compared RROC scores between groups, with adjustment for follow‐up time for final RROC scores. Subgroup analyses were performed among unruptured and ruptured aneurysms. Results 329 patients with 367 aneurysms were included, of which 163 were &lt;3mm and 204 were ≥3mm. Median age was 59 years (IQR: 48‐67) for the &lt;3mm group and 66 years (IQR: 55‐74) for the ≥3mm group (p&lt;0.001). Aneurysms were ruptured in 39.3% of the &lt;3mm group and 27.0% of the ≥3mm group (p=0.01). Interventions included coiling (132, 36.0%), stent‐assisted coiling (113, 30.8%), clipping (46, 12.5%), flow diversion (69, 18.8%), NBCA (3, 0.8%), and coiling + flow diversion (3, 0.8%) ( Table 1). There were no statistically significant differences in RROC or safety outcomes between &lt;3mm and ≥3mm aneurysms, either in the overall population or within unruptured and ruptured subgroups. However, &lt;3mm aneurysms tended to have better RROC scores post‐procedure (cOR=5.52, p=0.12) and at last follow‐up (cOR=2.41, p=0.20), as well as lower retreatment rates for unruptured aneurysms (OR=0.29, p=0.12). For ruptured aneurysms, post‐procedure RROC scores and retreatment rates were similar, but smaller aneurysms tended to have better predicted RROC scores at the last follow‐up (cOR=2.02, p=0.33). Complications, vasospasm, and mortality rates were similar between aneurysm size groups, both for unruptured and ruptured aneurysms. Conclusion Most patients achieved complete occlusion, regardless of aneurysm size, and did not require retreatment. Treatment outcomes do not differ significantly between very small aneurysms and those &gt;3mm. Table 1: Procedural and Outcome Characteristics Results for RROC scores and retreatment are presented as predicted probabilities with 95% confidence intervals. Predicted probabilities for RROC scores were derived from ordinal regressions, while those for retreatment were obtained from logistic regressions. Interventions and safety outcomes, including complications, vasospasm, mortality at 1 year, and mortality at any timepoint, are presented as raw data with n/N (percentage of total). P‐values for efficacy outcomes related to RROC and retreatment were calculated using two‐sided z‐distributions following regression analyses, and p‐values for safety outcomes were determined using Fisher's exact test. Complications included loss of coil, leakage, compromised M2 branch, repositioned clip, and direct ccf.

REVIEW OF PARAMETERS INFLUENCING WIRELESS ENERGY TRANSMISSION BY MAGNETIC INDUCTION

In this review article, we present a detailed study and discussion of wireless energy transfer systems based on studies in the literature, with the help of Python programming software. Starting from the basic element of wireless transmission by magnetic induction, i.e. the coil, through a magnetostatic study we have highlighted the impact of geometry, coil misalignment and coil loss factors on these transmission systems. We have also shown that parameters such as coupling coefficient and frequency can improve transmitted power and efficiency. A summary of the latest research in this field will also be given.

Efficiency Optimization of LCL-Resonant Wireless Power Transfer Systems via Bidirectional Electromagnetic–Thermal Coupling Field Dynamics

This paper delved into the thermal dynamics and stability of Wireless Power Transfer (WPT) systems, with a focus on the temperature effects on the coil structure. Using the Finite Element Method (FEM), this study investigated both unidirectional and bidirectional coupling field simulations, assessing their impacts on the transmission efficiency of LCL-resonant WPT systems. The boundary conditions and processes of the electromagnetic–thermal coupling field related to coil loss were analyzed, as well as the dynamic thermal balance in the bidirectional coupling field model. It was found that there is a significant temperature variation across the coil, with the highest temperatures at the central position and the lowest at the edges. This temperature rise notably changed the electrical parameters of the system, leading to variations in its operating state and a reduction in transmission efficiency. A constant coil voltage control strategy was more effective in mitigating the temperature rise compared to a constant coil current strategy, providing valuable insight for enhancing the efficiency and stability of WPT systems.

Structural Optimization of a Giant Magnetostrictive Actuator Based on BP-NSGA-II Algorithm

This study introduces an integrated structural optimization design method based on a BP neural network and NSGA-II multi-objective genetic algorithm. Initially, a two-dimensional axisymmetric finite element model of the Giant Magnetostrictive Actuator (GMA) was established, and the coupling simulation of the electromagnetic field, structural field, and temperature field was conducted to obtain the GMA’s performance parameters. Subsequently, the structural parameters of the GMA magnetic circuit, including the magnetic conducting ring, magnetic conducting sidewall, magnetic conducting body, and coil, were used as inputs, and the axial magnetic induction intensity, uniformity of axial magnetic induction intensity, and coil loss on the Giant Magnetostrictive Material (GMM) rod were used as outputs to establish a back propagation (BP) neural network model. This model delineated the nonlinear relationship between structural parameters and performance parameters. Then, the BP-NSGA-II algorithm was applied to perform multi-objective optimization on the actuator’s structural parameters, resulting in a set of Pareto optimal non-dominated solutions, from which a set of optimal solutions was obtained using the entropy weight method. Finally, simulation analysis of this optimal solution was conducted, indicating that under a 5 A power supply excitation, the maximum axial magnetic induction intensity on the optimized GMM rod increased from 0.87 T to 1.12 T; the uniformity of axial magnetic induction intensity improved from 93.1% to 96.5%; and the coil loss decreased from 7.79 × 104 W/m3 to 4.97 × 104 W/m3. Based on the optimization results, a prototype actuator was produced, and the test results of the prototype’s output characteristics proved the feasibility of this optimization design method.

Instantaneous AC Loss and Inductance Measurement of HTS Coil With Finite-Data-Window Least Squares

Instantaneous AC Loss and Inductance Measurement of HTS Coil With Finite-Data-Window Least Squares

Study on Thermal Characteristics of Winding under Inter-Turn Fault of Oil-Immersed Transformer

The inter-turn fault is a common fault of oil-immersed transformers. Due to the deterioration of inter-turn insulation, its resistance decreases, which leads to an increase in the winding coil current and loss, causing the winding temperature to rise. Therefore, analyzing the electrothermal characteristics of inter-turn short circuit faults in oil-immersed transformers can provide a theoretical basis for the diagnosis of inter-turn faults in transformers. This paper studies the equivalent circuit under inter-turn faults and establishes a field–circuit coupling model to calculate the current characteristics under different inter-turn short circuit faults of transformers. The distribution of coil losses under faults is calculated as thermal source excitations, and a thermal–fluid-coupled calculation model for oil-immersed transformers is established. After the experimental verification, it is found that both the errors between the winding and tank surface temperatures do not exceed the acceptable limits, validating the effectiveness of this model. Using this model to calculate the temperature distribution for various inter-turn short circuit faults in transformers reveals their hot-spot characteristics. The results indicate that under inter-turn fault conditions, the temperature at faulty turns will gradually increase towards a limit, eventually leading to coil damage. This research provides theoretical support for enhancing transformer detection and diagnostic capabilities.

Performance evaluation of homogenization techniques for proximity losses in PCB coils applied to inductive devices

Energy efficiency is the primary objective in optimal design of inductive power components. This goal is totally aligned with the minimization of power losses in the coils. Typically, coils have been constructed by wire winding but, more recently, the utilization of printed circuit board (PCB) constructions has become more common due to their advantages, i. e. low profile and ease of fabrication, among others. At the operating frequencies of magnetic power devices, multi-conductor cabling with litz structure is required to reduce losses. PCB loss optimization procedure involves determining the number and size of the tracks. Numerical simulation is a very powerful tool to obtain the parameters of magnetic devices. However, including the internal structure of multi-track wiring in the numerical simulation implies a very high computational cost and a low accuracy of the results, because the size of the tracks is very small. Techniques of homogenization of the cabling are used to overcome such difficulty, disregarding the internal structure in order to determine the fields in the system and their electrical equivalent by means of computational simulation. The coil losses are further determined on the basis of the characteristics of the cabling as well as of the surrounding fields. The preceding procedure has proven to be suitable for cables composed of strands of circular cross-section, but should be adjusted to apply to tracks of rectangular cross-section. In this paper, different homogenization techniques for PCB coils have been proposed and evaluated. A highly symmetric reference system is selected to reduce the computational cost of numerical modeling, but the conclusions can be applied to more complicated geometries without loss of generality. Finally, the results of the different homogenization techniques have been validated by comparison with experimental results.

3-D Modeling of AC Loss in D-Shaped HTS Coils Using $H$ and $T$-$A$ Formulation-Based Finite Element Methods

3-D Modeling of AC Loss in D-Shaped HTS Coils Using $H$ and $T$-$A$ Formulation-Based Finite Element Methods

Optical Fibers Characterization for Macrobending Sensors

The article delves into characterizing macrobending losses in optical fiber coils for use in diverse sensors. It examines Single-Mode Fiber (SMF) and Multimode Fiber (MMF) with step and graded index profiles incorporated into sensor coils of varying diameters and numbers of turns. The experimental configuration involves compressing the coils to monitor optical power loss caused by attenuation. The findings reveal that SMFs experience more significant macrobending losses than MMFs, while the graded index fiber exhibits notable resistance to bending. These results offer valuable guidance for fiber selection and sensor design considerations.

Numerical Simulation on AC Loss in REBCO Stacks and Coils Carrying Non-Sinusoidal Currents

Numerical Simulation on AC Loss in REBCO Stacks and Coils Carrying Non-Sinusoidal Currents

Experimental AC loss study on REBCO coil assemblies coupled with an iron cylinder

In high-temperature superconducting (HTS) power devices, the presence of iron cores changes the magnetic field profile around the HTS coil windings, potentially affecting their AC loss characteristics. AC loss measurements for HTS coil windings coupled with an iron core using the electrical method can lead to a significant error, owing to the indirect estimation of the iron core loss through using a copper test coil. To investigate the cause of the experimental error and the influence of an iron core on coil AC losses, transport AC losses of REBCO double pancake coil (DPC) assemblies coupled with an iron cylinder were measured. A 40-turn 1DPC and an 80-turn 2DPC assembly wound with 4 mm SuperPower wire were employed in the measurements. To ensure the same iron core loss using the HTS coil assembly and the copper coil, 2D finite element method simulations were conducted iteratively to design the iron core and the copper coil to get the same local magnetic field distributions in the designed iron core for the two cases. The main cause of the error is due to the difference in local magnetic flux densities in the iron core generated by the HTS coil assembly and the copper coil even when the ampere-turns of the coils are identical. We showed that the simulation-guided measurement method can assure accurate AC loss measurement in the HTS coil assemblies coupled with iron cores. Compared with the AC losses in the 1DPC and 2DPC coil assemblies without the iron cylinder, the presence of the iron cylinder significantly increases the coil losses. Frequency dependence is observed in the coil AC losses of the 1DPC and 2DPC assemblies when coupled with the iron cylinder. This is due to the eddy current induced in the iron cylinder generating a magnetic field, which influences the coil AC loss.

Calculation method of electromagnetic losses and hot-spots temperature of giant magnetostrictive transducer

Due to the complex energy conversion processes and limited avenues for heat dissipation in the giant magnetostrictive transducer (GMT). Large losses and elevated internal temperature rise are inevitable, this would bring into serious reliability problem for GMT. Accurately analyzing its electromagnetic losses and hot-spots temperature are crucial for designing and optimizing the transducer. High-power GMT typically use permanent magnet (PM) to provide a bias magnetic field for enhanced power density. Although, this structure could significantly reduce the volume of driving part, it also caused issues such as non-uniform magnetic field distribution and bias magnetic field, which have great influence on the magnetic energy loss and hot-spots temperature rise. The previous researches seldomly investigate these influences on total loss at GMT system level. Additionally, the differential excitation coil loss caused by AC resistance among multi-layers can’t be neglected, which can lead to variations in coil loss and temperature rise. Therefore, this paper proposed a detailed electromagnetic losses and hot-spots temperature rise calculation model from material level to GMT system level. This method can obtain the distribution of electromagnetic losses within multiple factors, and the hot-spots temperature rise considering the temperature non-uniform distribution. Firstly, we have developed a precise loss calculation model, which takes the influence caused by PM bias and non-uniform magnetic field on magnetic energy loss into account. Additionally, the proposed model could conclude the impact of inter-coil resistance variations on the eddy current loss in excitation coil. Secondly, based on of the non-uniform distribution of losses in driving part, using the divisional thermal modeling approach and a 2-D T-shaped equivalent thermal network, we further constructed a transient temperature calculation model for GMT. This approach can effectively improve the energy conversion efficiency of GMT, so as to enhance the thermal reliability of the transducer. Finally, a testing system for the loss-thermal of GMT was established to validate the effectiveness of proposed model. Results indicate that the average error between our loss calculation model and experimental results is 2.93%, while the corresponding error for without considering the above factors is 15.97%. This confirms the necessity of conducting a detailed electromagnetic losses calculation model. In addition, the average error of the temperature rise calculation model is less than 5%, while the error for without considering the losses distribution and heat dissipation paths difference is exceed 10%. In conclusion, our proposed method accords well with the measured results, and can provide significant fundamental for design and optimization of GMT.

Power Loss and Temperature Distribution in Coil of PFC Inductor with Air Gap for Multimode Operation

Power converters inherently display non-linear load characteristics, resulting in a high level of mains harmonics, and hence the necessity of implementing Power Factor Correction (PFC). Active PFC circuitry typically comprises an inductor and a power switch to control and alter the input current so that it matches, in shape and phase, the input voltage. This modelling of the waveforms can be performed by means of distinct conduction modes of the PFC inductor. The digital controller implemented in the constructed and investigated boost-type PFC converter can be programmed to operate in discontinuous conduction mode (DCM), continuous conduction mode (CCM), or a combination of the two. The individual modes of operation, via distinct PFC inductor current waveforms, impact the overall efficiency of power conversion and, by extension, temperature distribution in the magnetic component. This paper investigates how the examined conduction modes bear on distinct power-loss mechanisms present in the PFC inductor, including high-frequency eddy-current-generating phenomena, and the fringing effect in particular. As demonstrated herein, the DCM operation, for the set output power level, exhibits exacerbated power dissipation in the winding of the inductor due to the somewhat increased RSM value of the current and the intensified fringing magnetic flux at an air gap. The latter assertion will undergo further, more quantitatively focused research. Finally, the construction of the coil was optimised to reduce power loss by diminishing eddy-current mechanisms.

Experimental study on AC loss of 1G and 2G HTS coils with an identical structure, geometry and number of turns

Devices made of High Temperature Superconductor (HTS) will suffer AC loss during AC operations, which has unnegligible influence on energy consumption, overall efficiency, cooling cost, and operational stability of the devices. In this study, comparative measurements on 1G and 2G HTS coil samples with an identical structure, geometry, and number of turns were systematically conducted with a calorimetric method at different current values (I rmss) and frequencies (fs). The AC loss characteristics of the HTS samples were analyzed and compared based on the experimental results. The results show that eddy current and coupling play a more dominant role than magnetic hysteresis in the total AC loss of coils made of HTS tapes. The AC loss of both samples increases with I rms and f, but the AC loss is more sensitive to I rms than to f. Under the same conditions, the 1G coil sample has a slightly larger AC loss than the 2G one.

Energetic and exergetic assessment of a ground source heat pump system using low temperature resources in a tropical climate

The energy crisis is a global issue which all nations are involved with it. To this purpose, scientists are developing new energy sources that have less downsides than traditional energy sources. In the current investigation, a ground source cooling system is built in a 234 m2 office building at the gas company bureau in Qom province, Iran, which has a tropical environment. In this climate, which the ground temperature is almost 21 °C, some closed vertical type ground coil with about 170 m depth is constructed for the system, and then some measurements are recorded. The system has been evaluated using the extracteddata and energy and exergy evaluations have been conducted. The outputs show a great sensitivity of the coefficient of performance to the outlet ground coil temperature and the exergy analysis demonstrates that the exergy loss of the ground coil is slightly increased over the workday and the heat pump with exergy dissipation and exergy loss coefficient of 6.4 kW and 0.22 has higher rate of irreversibility compared to other components. Moreover, the average values of Coefficient of Performance (COP) and outlet temperature of ground coil during a workday were obtained as 4.43, 27.43C respectively.

A Fast Calculation Method Based on Full-Boundary Magnetic Field Simulation for Calculating AC Loss in Bi-2223 HTS coils of Double-Stator HTS Machine

A Fast Calculation Method Based on Full-Boundary Magnetic Field Simulation for Calculating AC Loss in Bi-2223 HTS coils of Double-Stator HTS Machine