Traditional Winding Research Articles

Design of Interleaved Winding for Multilayer Planar Inductor and Its Application in Reducing Current Ringing of LLC Resonant Converter

To enhance the power density of LLC resonant converters, multilayer planar inductors are required. However, multilayer planar inductors have high parasitic capacitance, which may cause inductor current ringing in LLC resonant converters, leading to EMI problems. In this paper, it is found that by using interleaved winding inductors, compared with traditional winding inductors, the parasitic capacitance of multilayer planar inductors is reduced, which can reduce current ringing, without sacrificing power density and increasing manufacturing complexity. The method used to analyze current ringing is to establish an impedance model, and the parasitic capacitance of the interleaved winding inductors is verified by FEM simulations. The analysis is validated in an LLC resonant converter prototype.

Comparison of Permanent Magnet Synchronous Machines for Hybrid Light Aircraft with traditional and additive winding technologies

Electrical motors are key components in the electrical transition required for greenhouse gas reduction programs. Future aircraft will certainly employ electrical motors for primary and secondary surface control, for landing gear and for other actuations such as high-lift systems, and they will also need electrical motors for propulsion. The motors pose the hardest challenge due to the high-power density required. Hybrid-Electric propulsion represents one of the most important topics in the aerospace industry and offers an opportunity to pursue the electrification change especially in light aircraft segments. The focus of this paper is the comparison among permanent magnet synchronous motors for Hybrid Light Aircraft propulsion with traditional and additive winding technologies.

Analytical Calculation and Experimental Validation of Litz Wires Axial Thermal Conductivity

Litz wires are widely used in electrical machines with reduced AC losses, compared to traditional random winding. The reduced AC losses can improve both electrical machines electromagnetic performance, such as efficiency and thermal performance. Thermal aspect is identified as a key enabler for next generation high power density electrical machines, where thermal modelling plays a critical role. Equivalent slot thermal conductivity is one of the most challenging parameters to be determined in the process of thermal model development, due to various components, such as copper, insulation, and impregnation resin. There are extensive literatures where the litz wire thermal conductivity in the radial direction are reported. However, the thermal conductivity in the axial direction is not well studied, which is critical to determine the heat transfer, such as for electrical machines with end winding spray-cooling system. In this paper, the axial thermal conductivity is investigated with analytical calculations and experimental validation. Firstly, 9 litz wire samples are selected with various types, such as rectangular and circular shapes, with varnish process and without. Two different analytical methods are then introduced and presented to calculate the litz wire thermal conductivity in axial direction, based on equivalent length theory and equivalent medium theory, respectively. Finally, experimental tests are conducted, and results are compared to those obtained from the proposed analytical methods. Guidelines are also provided to predict the litz wire axial thermal conductivity in this field.

Effect of the grain boundary character distribution on the sulfur corrosion behaviour and mechanisms of copper windings under different high temperatures

AbstractAs a typical failure phenomenon in transformers, sulfur corrosion has garnered significant attention in the field of high‐voltage engineering. Grain boundary character distribution (GBCD) copper windings have been introduced to enhance sulfur corrosion resistance by slowing down intergranular corrosion. In this study, the sulfur corrosion behaviour and mechanisms of the GBCD copper windings under various temperatures were experimentally and theoretically studied. Results show that GBCD can enhance the corrosion resistance of copper in liquid environments. With the increase in temperatures, the insulating properties of oil and papers in traditional copper windings experience notable degradation, while GBCD copper windings show more stable insulating behaviours. In addition, modelling of grain boundary energy indicates that the grain boundary structure of GBCD copper windings has a lower average interface energy of 0.170 eV/Å2. Calculations of reaction thermodynamics show that GBCD copper windings possess a higher failure temperature (135.2°C) and inhibition degree (activation energy) of the sulfur corrosion (32,557.62 J/mol), revealing the stability and enhanced sulfur corrosion resistance at elevated temperatures.

Optimization and experimental validation of reinforcing fibers winding pattern for carbon/carbon composite crucible preform

In order to address the problem of transition slip between the cylindrical segment and the ellipsoidal head segment of the carbon/carbon composite crucible preform with asymmetrical structure during the winding process, a winding pattern combining geodesic and non-geodesic is presented innovatively. Firstly, the formulae for the winding angle and the winding central rotation angle of the crucible cylindrical segment and the ellipsoidal head segment are established, and the fourth-order Runge-Kutta numerical method is employed for parametrical design. The two-tangent point winding path is determined by analyzing the effect of the cylindrical segment’s winding pitch, different ellipsoidal head segment heights, and slip coefficient on the winding angle. Secondly, the needle disk winding method is proposed to address the slight winding angle at the open end of the cylinder, making it easier to hang the yarn. Finally, the experiment on dry yarn winding of 3k carbon fiber (linear density: 198 g/km) is carried out. The results indicate that the relative error rate between the actual winding angle and the theoretical design angle differs by no more than 1.66%, demonstrating that carbon fibers can be stably and uniformly wound onto the surface of the carbon/carbon composite crucible preform. Compared to the traditional manual winding method, the winding pattern enhances winding efficiency, ensures carbon fibers’ uniformity and structural stability, and provides a new technological approach to producing high-performance composite materials.

Analytical Thermal Model of Slot for Electric Propulsion Motor in Electric Aircraft

Accurate prediction of temperature is critical for evaluating electric propulsion motor performance. This paper presents an analytical thermal model of slot for the prediction of temperature. According to the heat transfer in the slot, the shortcomings of the traditional winding model are pointed out. This paper adopts a more advanced layered model. The number of layers is calculated analytically. Based on Laplace's equation and Poisson's equation, the thermal resistance and temperature rise of each layer are analytically calculated. The layered windings and insulation are equivalent to a heat-generating entity whose thermal resistance and temperature rise are equal to those of the layered slot. The equivalent thermal conductivity of heat-generating entity can be obtained. The slot is equivalent to a heat-generating entity through the analytical method, which reduces the computational complexity of the simulation. The experiments are employed to validate the accuracy of the proposed model.

Design and manufacture of a Type V composite pressure vessel using automated fibre placement

Automated fibre placement (AFP) can improve composite pressure vessel design by enabling selective reinforcement and allowing a wider range of fibre orientations than the traditional filament winding process. This paper presents the development of an AFP Type V composite pressure vessel with a design working pressure of 4.22 MPa made using a novel collapsible mandrel. The design process is presented along with a thickness control strategy for the AFP parts using ply drops. The tank was manufactured, and the thickness was validated using 3D scanning. The masses of the AFP parts were also measured to within 2.23% of the predicted values. The finished tank was hydrostatically pressure tested to understand the leakage behaviour. Defects and difficulties encountered in this prototype are discussed and opportunities for future work and improvements have been identified.

3D winding path modeling of overwrapped pressure vessels with novel mesh-based directional projection and normal adaptive convex helix algorithms

Filament winding is a technique that precisely places continuous fibers along a preset path on a rotating mandrel. However, traditional 2D winding paths based on the original mandrel surface ignore the effect of thickness stacking on doffing points. To physically simulate the build-up of tows on the mandrel, a novel numerical method, including the mesh-based directional projection (MDP) and normal adaptive convex helix (NACH) algorithms, is proposed. The MDP algorithm is employed to sort out tow overlaps in the thickness direction, and is 200 times more efficient than the existing algorithms, such as the backward search algorithm. Subsequently, the “cliffs” generated in the overlap removal process are smoothed by the NACH algorithm. Furthermore, the advantages of these two algorithms in terms of efficiency, reliability, and universality are discussed in detail. In summary, a method for developing a physical-based 3D path and ever-updating workpiece contour of pressure vessels is proposed, which serves as an essential reference for high-precision winding and workpiece shape optimization.

High-Frequency Transformer Design With Medium-Voltage Insulation for Resonant Converter in Solid-State Transformer

A Solid-state transformer (SST) can directly convert medium voltage to low voltage (e.g. 400 V) with minimized power-conversion stages. The transformer in the DC-DC module not only provides medium voltage insulation but also significantly affects the power density of the module. In this paper, an innovative compact transformer structure is proposed to handle medium voltage insulation using an insulation coordination with epoxy, bobbin, shielding layer and stress-control layer. A brand-new bobbin design and related fabrication process ensures a partial-discharge-free insulation. Besides traditional core loss and winding loss, high-frequency related core loss and shielding loss is modeled in detail for an accurate loss evaluation. A simple and comprehensive multi-parameter, multi-objective optimization process is proposed to achieve the size and loss trade-off. The transformer prototype passes the related insulation tests, following the standard IEEE Std. C57.12.01. Finally, the design is demonstrated on a 15 kW, 200 kHz CLLC converter with 98.9% peak efficiency and 3.8 kW/L power density.

AC Loss Analysis and Measurement of a Hybrid Transposed Hairpin Winding for EV Traction Machines

To address the problem of high-frequency AC loss of hairpin winding, a hybrid transposed hairpin winding (HTHW) scheme, which combines flat wire and litz wire, is proposed. The HTHW can effectively reduce the high-frequency AC loss, while maintaining a relatively high slot fill factor. In this paper, the AC loss generation mechanism under high-frequency excitation is firstly analyzed. Then, based on the field-circuit-coupled finite element method, the current density distribution and AC loss of hairpin winding with different transposed topologies are calculated and compared. Finally, an experimental platform enabling direct measurement of hairpin winding loss is built to verify the simulation. The simulation and experimental results show that the AC loss of the proposed HTHW is much lower than that of the traditional hairpin winding, for medium to high running frequency. In our case, the AC and DC resistance ratio of the presented HTHW is 2.12 at the frequency of 1200 Hz, contrasting that of the ratio of traditional hairpin winding, which is 10.2.

Analysis of a Capacitive Sensing Circuit and Sensitive Structure Based on a Low-Temperature-Drift Planar Transformer.

In space gravitational-wave-detection missions, inertial sensors are used as the core loads, and their acceleration noise needs to reach 3×10−15 ms−2/Hz at a frequency of 0.1 mHz, which corresponds to the capacitive sensing system; the capacitive sensing noise on the sensitive axis needs to reach 1 aF/Hz. Unlike traditional circuit noise evaluation, the noise in the mHz frequency band is dominated by the thermal noise and the 1/f noise of the device, which is a challenging technical goal. In this paper, a low-frequency, high-precision resonant capacitor bridge method based on a planar transformer is used. Compared with the traditional winding transformer, the developed planar transformer has the advantages of low temperature drift and low 1/f noise. For closed-loop measurements of capacitive sensing circuits and sensitive structures, the minimum capacitive resolution in the time domain is about 3 aF, which is far lower than the scientific measurement resolution requirement of 5.8 fF for gravitational wave detection. The capacitive sensing noise is converted to 1.095 aF/Hz in the frequency band of 10 mHz−1 Hz. Although there is a gap between the closed-loop measurement results and the final index, the measurement environment is an experimental condition without temperature control on the ground; additionally, in China, the measurement integrity and actual measurement results of the capacitive sensing function have reached a domestic leading level. This is the realization of China’s future space gravitational wave exploration.

Mechanical performance of composite flat specimens and pressure vessels produced by carbon/epoxy towpreg dry winding

The main purpose of this study is to evaluate the effects of certain processing parameters on the mechanical performance of carbon/epoxy towpreg wound composite structures. For this purpose, composite sample productions and their evaluations were conducted in two steps. In the first step, dry winding of carbon/epoxy towpregs was used to produce flat composite plates. Their evaluation was performed by rheological analysis, interlaminar shear tests, and unidirectional tensile tests. In the second step, towpreg dry winding was used to produce composite pressure vessel samples. Their performance was evaluated by observing the effects of various winding process parameters on the safety of the vessels via hydrostatic burst pressure tests. Compared to the traditional wet filament winding, the main difficulty observed was maintaining the “straight towpreg path” necessary for efficient winding operations. This problem was prevented by applying higher tension forces during dry winding. Evaluation of the hydrostatic burst tests in terms of burst pressure, hoop strain and safe failure mode revealed that the optimum pressure vessel performance could be obtained in the vessel samples with “helical-hoop-helical winding layer sequence.” On the other hand, use of “complex helical pattern” resulted in no advantages at all, due to basically higher number of undulation zones acting as stress concentration zones.

A Comprehensive Design Guideline of Hairpin Windings for High Power Density Electric Vehicle Traction Motors

The rapidly increasing demand on power density levels of electric vehicle (EV) drive systems is pushing the boundaries of traction motor performance. Hairpin windings are becoming a popular option for EV motors due to their reduced dc losses and improved heat dissipation capability when compared to traditional random windings. In this article, a comprehensive design approach of hairpin winding layouts is first presented. The flexibility and limitation of end-winding patterns are thoroughly investigated in terms of basic pin connections, special jumpers, transposition, parallel branches, terminal positions, phase shift, winding pitches, as well as slot–pole combinations. To address the challenge of much reduced practical layout options with increased slot number per pole per phase, two novel hairpin winding designs are proposed. A 160-kW, 18 000-r/min permanent magnet (PM) traction motor featuring the new winding layout with 54-slot, 6-pole is developed using a multidomain design platform, which puts special focus on the conductor size optimization. The advantages of the designed motor are clearly revealed by comparison with the more traditional 48-slot, 8-pole counterpart. Finally, a corresponding stator prototype with the proposed hairpin winding is built to validate its manufacturability.

Strategies for improving the force performance of a superconducting linear synchronous motor

Combined with superconducting technology, an electrodynamic suspension train can reach a higher traveling speed by taking advantage of the strong magnetic field generated by high-temperature superconducting (HTS) magnets. However, a HTS linear synchronous motor (LSM) in a propulsion system typically uses an air-core structure to reduce the normal force. As a result, excessive propulsive force ripple occurs due to magnetic circuit divergence and a large air gap, which leads to an uncomfortable ride and unexpected mechanical resonance. To reduce this ripple, this study first improves the traditional short-pitch winding structure of the stator. By staggering the double-layer coils of the stator, the ripples of the magnetic flux density generated by the upper and lower coils change from superposition to suppression. Then, the propulsive force of a pair of pole magnets of the HTS-LSM under this structure is analyzed, and its primary ripple frequency is 6 times the fundamental frequency. By installing two pairs of magnets in a bogie and staggering them by a 30° electrical angle, the peak and valley of the propulsive force of the two magnets are staggered so that the total propulsive force waveform of the bogie can be smoothed as much as possible. Concurrently, the AC loss generated by the alternating magnetic field on the HTS magnets can be reduced. Also, this study investigates the influence of the short pitch factor on the propulsive force, and the ripple can be suppressed by reducing the factor.

Grid ionization chamber based on stainless steel woven wire mesh

The grid electrode of the grid ionization chamber (GIC) is devoted to eliminating the dependence of the anode pulse amplitude on the initial position and orientation of the ionization. The traditional methods of grid production require cumbersome processes and advanced instruments. In this paper, a bonded stainless steel woven wire mesh (SSWWM) grid electrode manufacturing method is proposed. Compared with the traditional grid electrode, the SSWWM grid features the advantages of simple fabrication, low cost, and high mechanical strength. The energy resolutions of the 40-mesh, 60-mesh and 80-mesh SSWWM grids and orthogonal mesh grid realized by the traditional wire winding method were tested using an 241Am source (around 5.486 MeV). The results show that the optimum energy resolution of the SSWWM and orthogonal mesh grids is approximately 47 keV full width at half-maximum (FWHM). The optimal energy resolutions of the 40-mesh and 60-mesh SSWWM grids are comparable, but the initial operating voltages corresponding to the energy resolution plateau are different, mainly because of the effect of the different geometric parameters of the SSWWM grid on the electron transmittance. A simulation program was used to study the electron transmittance of the SSWWM grid. The simulation results are in agreement with the experimental results, indicating that the simulation program can be used as a reference for the selection of the geometric parameters of the SSWWM grid.

Critical current degradation behavior in Bi-2212 round wires under cyclic transverse stress

Bi-2212 multi-core round wires without anisotropy can be made into Rutherford cable and cable-in-conduit conductor (CICC) using traditional cable winding technology, which has been widely used in high-field magnets such as fusion reactors. Recently, Bi-2212 is considered to be one of the most promising potential superconducting magnet materials in the Chinese Fusion Engineering Test Reactor (CFETR) magnet. However, Bi-2212’s ceramic structure and Ag/Mg alloy sheath make it susceptible to stress. Due to the complicated working environment of magnet, Bi-2212 round wire is bound to be affected by cyclic electromagnetic stress and thermal stress. Several researchers have reported the performance of Bi-2212 round wire under axial tension strain and tension fatigue. And the impact of indentation on the critical current of Bi2212 round wire has been studied. However, the study of transverse stress characteristics has not been reported. In this work, critical current degradation under cyclic transverse stress for Bi-2212 round wires prepared by different heat treatment processes was studied. The initial critical current Ic0 at 77 K for sample sintered at overpressure with annealing was the highest and Ic0 for sample sintered at atmospheric pressure without annealing was the lowest. The greater transverse fatigue stress will accelerate the process of fatigue.

Analysis of winding MMF of PMSM with multi-phase and multi-layer layout using holospectrum method

A holographic spectrum method (HSM) of multi-phase and multi-layer winding magnetomotive force (MMF) for 12-slot/10-pole combination with fractional-slot concentrated-winding (FSCW) is proposed in this paper. Taking two kinds of traditional winding layout as example, amplitude and phase distribution of the vth harmonic are calculated. The holospectrum of the multi-phase and multi-layer winding are derived based on three-phase single-layer (TP-SL) and three-phase double-layer (TP-DL) holospectrum theory. Then the finite element method (FEM) is used to validate the resultant winding MMF calculated by the holospectrum method. Results show that two methods have a good consistency in changing tendency. Prototype manufacture and test of axial-flux PMSM with a double-three-phase four-layer (DTP-FL) winding have been completed. A load experiment with two groups of resistance is established to validate its output power of axial-flux permanent magnet synchronous machine (PMSM). The temperature distribution of axial-flux PMSM is evaluated with PT100 and infrared thermal imager. The experiments shows that the axial-flux PMSM runs at a relative temperature rise.

Hardware-software complex for experimental research of electric drives of asynchronous motors with squirrel-cage rotor with traditional winding and motors with combined winding

THE PURPOSE. Modern requirements for electric drives impose increasingly stringent conditions for energy efficiency, dimensions and weight. The weight and size parameters are especially noticeable in relation to the rapidly developing electric transport. The achieved technological limits practically do not give tangible results in improving the characteristics of known structures, so there is a struggle for units of percent and fractions of a percent in terms of increasing the efficiency of equipment.MATERIALS. Debugging and fine-tuning of electric drive elements requires numerous tests on research benches using measuring channels and analog-to-digital conversion (ADC), digital-to-analog conversion (DAC), digital-to-digital conversion (DDC).RESULTS. The creation of research stands implies the development of a hardware-software complex (HSC) based on high-speed computing devices. The structure of the HSC included the developed frequency converter with the possibility of adjusting the algorithms for controlling the electric motor and the mathematical model of the electric motor itself. The object of experimental research was prototypes of electric drives based on asynchronous electric motors with a squirrel-cage rotor and a combined stator winding.CONCLUSION. The article discusses ways to organize the measuring and control channels of the measuring and information system of the research stand, which makes it possible to study samples of asynchronous electric motors in idling and under load modes.

Analysis of a Sinusoidal Rotor Segments Axial Flux Interior Permanent Magnet Synchronous Motor with 120-degree Phase Belt Toroidal Windings

Axial flux permanent magnet (AFPM) motors are widely applied in many applications due to their performance advantages. A novel AFPM which owns a special winding form (120-degree phase belt toroidal windings) and a distinct rotor structure (sinusoidal rotor segments) is proposed in this paper to further improve the torque density of this kind of machine. First, the structure and working principle of the 120-degree phase belt toroidal windings sinusoidal rotor segments AFPM interior synchronous motor (120D-TWSRSAFPMISM) are clarified. Then, the design formula and crucial parameters of the motor are presented. Subsequently, the cogging torque is optimized by dividing the magnet grouping. Finally, the characteristics of the 120D-TWSRSAFPMISM are analyzed and compared with those of the traditional toroidal windings sinusoidal rotor segments AFPMISM (T-TWSRSAFPMISM) and another T-TW motor without the sinusoidal rotor segments (T-TWAFPMISM) by finite element method (FEM). The results show that the 120D-TW can significantly increase the back electromotive force (EMF) compared with the T-TW, and the sinusoidal rotor segments can increase the air-gap flux density compared with the traditional interior rotor. Therefore, the 120D-TW and sinusoidal rotor segments are combined in the AFPM motor. This combination can further increase the torque density compared with the contrast motors.

Tension system design based on heated-mandrel winding process

Heated-mandrel winding is the main process of modern composite material molding because of its characteristics of winding and curing in one step. Winding tension is a key factor in the molding process and has an important impact on the molding effect. Excessive winding tension will cause the inner looseness and outer tightening, and too small winding tension will cause the outer looseness and inner tightening. In short, the stratification will occur during the curing as long as the winding tension value is not set properly, which will seriously affect the molding quality of composite materials. The tension system of single winding process is difficult to apply to the heated-mandrel winding process because winding and curing are separate in the traditional single winding process, there is no need to consider the diversification of parameter state caused by curing reaction in winding process. In the heated-mandrel process, the balance of forces between adjacent layers is broken, the stress changes in adjacent layers affected by the temperature field are considered during winding. The tension values are obtained by adopting the tension system model established in this paper and the traditional finite element iterative search calculation method is replaced by numerical analysis method. An analytical algorithm for the method of winding with tension as the interference fit of the thin layers is adopted in the calculation procedures and the nonlinear tension solution problem is converted into a linear displacement-stress calculation problem. The lengthy and complicated traditional tension calculation method is simplified.