Rectangular Copper Wire Research Articles

Model-based closed-loop process control for the manufacturing of hairpin coils

As a consequence of the increasing market share of hybrid and all-electric mobility solutions, there is a need for robust manufacturing technologies that enable the efficient production of powerful electric traction motors in automotive industry. In the context of high-quality distributed stator windings, the so-called hairpin technology already meets the automotive demand regarding productivity – but process reliability is still limited by variations in the mechanical and geometric properties of the enameled rectangular copper wire leading to different springback effects within the forming processes. Against this background, a model-based closed-loop process control for the sequential tool-bound bending of hairpin coils is introduced and validated in this paper.

Method for analyzing welding speed and beam deflection and its effect on laser welded hairpin windings for electric drives

Individual mobility is in the process of transformation to electric drives. In the manufacturing process of hairpin windings rectangular copper wires must be contacted. Therefore, high laser power and high welding speed are used in combination with small geometric shapes. For these reasons, the geometric accuracy at different welding speeds is investigated on two optical setups. Furthermore, the process-related deflection of the laser beam must be considered. The method developed in this paper allows to visualize the welding path in the welded position. It is shown, that above a certain deflection, the F-Theta optics lead to an aberration of the focal point in the application plane. This results in a lower energy input. Computed tomography is used to demonstrate this effect and its impact on the cross-sectional area of welded hairpins. For both optical setups, a reduction of the path geometry dimensions can be observed with an increasing welding speed.

Electron beam welding of rectangular copper wires applied in electrical drives

The so-called hairpin winding technology, which is specially tailored to electrical traction components, deploys rectangular plug-in copper wires in the stator. The fusion welding of the adjacent wire ends is associated with challenges due to the high thermal conductivity as well as the porosity formation of the copper. During this study, the electron beam (EB) welding of electrolytic tough pitch (ETP) and oxygen-free electronic grade (OFE) copper connectors was investigated. Subsequently, the specimens underwent X-ray computed tomography (CT) and metallographic examinations to characterize the joints. It was discovered that the residual oxygen content of the base material is responsible for the pore formation. With only a very low level of oxygen content in the copper, a porosity- and spatter-free welding can be reproducibly realized using the robust EB welding technology, especially for copper materials. By optimizing the parameters accordingly, joints exhibiting a low level of porosity were achieved even in the case of the alloy containing a high amount of residual oxygen. Beyond this, detailed analyses in terms of pore distribution were carried out and a good correlation between technological parameters and welding results was determined.

Reduction of AC Copper Loss in Rectangular Copper Wire using Magnetic Path Control Technology

Reduction of AC Copper Loss in Rectangular Copper Wire using Magnetic Path Control Technology

High Torque Density Fractional-Slot Concentrated-Winding Axial-Flux Permanent-Magnet Machine with Modular SMC Stator

In this article, the implementation of a single-stator double-rotor fractional-slot concentrated-winding (FSCW) axial-flux permanent-magnet machine is presented to verify a simple and reliable structure design and oil-immersed cooling of the stator with modular soft magnetic composites (SMC) core. Due to the yokeless and segmented stator, the process of embedding the windings into the stator teeth will probably become simpler. By preforming rectangular copper wire, the shorter end-winding length and higher fill factor can be achieved. In order to eliminate eddy current losses and manufacturing costs, the fiberglass epoxy is used for the supporting components of the fixation for modular SMC stator and PMs, which is a nonmagnetic and nonconductive material. Hence, the robustness of stator and rotor are taken into account due to the stator modularity weakening effect on strength. Meanwhile, a fully sealed stator with oil-immersed cooling is proposed to enable the current density of 20 A/mm2 in the armature windings for stable operation. The electromagnetic properties, including in magnetic field distribution, torque capacity, and flux-weakening ability, are performed based on the three-dimensional finite-element analysis, as well as the mechanical performance. The coupled thermal and computational fluid dynamics model is built to predict the flow and temperature distribution inside stator with oil-immersed forced cooling. The construction and experimental verification of a full-scale 30-kW prototype are elaborated to verify the predicted performances in terms of torque density, structural strength, and cooling.

Characterization of Rectangular Copper Wire Forming Properties and Derivation of Control Concepts for the Kinematic Bending of Hairpin Coils

As a result of the continuously growing demand for electric vehicles, innovative production technologies must be developed to fulfill the high automotive requirements for productivity and quality in the manufacturing of electric drives. By providing advantages regarding the degree of automation, the productivity as well as the attainable filling factors in comparison to established round wire winding technologies, the hairpin technology shows a high potential for meeting the requested specifications but also technological weaknesses, especially concerning the process reliability. The referring production process of stators is normally based on the spatial forming of open, hairpin-shaped coils of enameled flat copper wire as well as subsequent joining and contacting processes. Consequently, the hairpin coils represent the elementary components of the process chain and can be either shaped by robust tool-bound or flexible kinematic bending processes that enable the shaping of different contours at moderate tool costs. In this paper, the essential mechanical forming and product properties of flat copper wires with different dimensions and insulation coatings are characterized by means of uniaxial tensile tests as well as metallographic analyses of the material structure, at first. Subsequently, the identified forming properties are correlated to the applied manufacturing processes drawing, rolling as well as continuous extruding and considered as limits of possible material variations. To evaluate the effect of fluctuating wire qualities on the robustness of kinematic hairpin bending processes, the fabrication tolerances are analyzed by finite element simulations, using the example of elementary kinematic bending operations and modeled changes of the material properties. Based on the knowledge of material-based process tolerances, different control concepts for the kinematic bending of hairpin coils are derived and compared based on technical as well as economic aspects.

Visualization and quantitative evaluation of eddy current loss in bar-wound type permanent magnet synchronous motor for mild-hybrid vehicles

This paper describes the conductor eddy current loss that occurs in a permanent magnet type synchronous motor with a distributed winding stator using a rectangular copper wire designed for mild hybrid system applications for small vehicles. Compared with the conventional round wire inserter method, the space factor can be improved and the coil-end length can be shortened by applying a so-called hairpin windings using a pre-formed into hairpin shape of bar conductor, and as a result, DC current resistance of the armature winding can be reduced. However, since the conductor cross-sectional area tends to increases, the conductor eddy current loss generated by the space harmonics linkage becomes too large to ignore. In order to study the reduction of the conductor eddy current loss, it is important to visualize the spatial leakage flux distribution which causes loss and finely analyze how the magnetic path is formed. Therefore, analysis of the conductor eddy current loss distribution generated in the bar-wound conductor is performed using the CAE model that faithfully reproduces the coil-end shape of the actual machine. Furthermore, it was qualitatively clarified what ratio of conductor eddy current loss at various driving points. Finally, the results of preliminary study on reduction of conductor eddy current loss are reported.

Thermal conductivity survey of different manufactured insulation systems of rectangular copper wires

Especially in high power applications, thermal design of magnetic field coils is a critical partof efficient electromagnetic system design. Since thermal expansion of the coil effects magnetic fieldgeometry, temperature drop across the windings should be kept as low as possible. Here the insulationsystem between wires guides ohmic heat to the surface of the coil and influences the total thermalperformance. Because of very less information about the general thermal performance and quality ofmanufactured multilayer insulation systems, the present survey investigates several variants made ofenameled wires and Polyimide film wrapped wires. Hereby, different joining technologies like bondingor backfilling determine the thermal conductivity, which obviously differs from values of individual rawmaterials. Best performance could be gained with a Kapton®–CR film wrapped wire, backfilled withhigh thermal conductivity resin. Finally, the survey concludes that manufactured insulation systemsdrop approximately ten to twenty percent of the thermal conductivity, which could be theoreticallyachieved by an optimal layer composition of individual raw materials.

Effect of continuous hybrid process on mechanical and electrical properties of rectangular pure copper wire

In this study, a continuous hybrid (CH) process applied with newly designed dies was proposed to manufacture a high strength and high electrical conductivity rectangular copper wire in a continuous way. The 2nd pass CH process with different processing routes, A and C, was numerically and experimentally carried out to check the practicality of the process and to investigate the deformation behavior of the commercially pure copper wire. Electron backscatter diffraction, tension and Vickers micro-hardness tests were employed to study the changes in the microstructure and mechanical properties of the wire. Electrical conductivity was also measured by a four-point probe method. According to the current investigation, the CH process with the new concept dies could impose relatively high plastic deformation without die change during the process and promote the accumulation of dislocation, resulting in grain refinement of the wire compared to the conventional wire drawing (WD) process. The mechanical strength and hardness values of the processed rectangular pure copper wire by the CH process were increased, and the electrical conductivity was relatively maintained compared to the one processed by the WD process. In particular, route C could produce wire with relatively uniform strength distribution. Route A might be adequate for the manufacturing of one-sided hardened rectangular wire such as the contact wire for rail electrification. It is demonstrated that the CH process can be applied to the rectangular wire manufacturing process and might be beneficial to produce high strength and high electrical conductivity copper wire for various applications.

Effect of Winding Coil Diameter on AC Insulation Breakdown Voltage of Polyamideimide/Nanosilica Wire

The AC insulation breakdown voltage was investigated for seven types of winding coils made of polyamideimide (PAI), flexural PAI (nanosilica 5 wt%) and anti-corona PAI (nanosilica 15 wt%) wires with various winding coil diameters of φ5, φ15 and φ25 mm. The winding coil was made of enameled wire with an enamel thickness of 30~50 μm, and the rectangular copper wire had a thickness of 0.77~ to 0.83 mm and width of 1.17~ to 1.23 mm, respectively. The insulation breakdown voltages of the original PAI coils with diameters of φ5, φ15 and φ25 mm were 7.30, 6.58, and 5.95 kV, respectively, and those values decreased as the winding coil diameter increased, regardless of the wire types.

LED-TV용(用) 전원장치에 적합한 Hybrid 초크 코일의 특성 해석에 관한 연구

This paper presents the intra capacitance modeling according to the winding method, section bobbin and coil structure for hybrid choke coil capable of the EMI attenuation of broad bands from lower frequency bands to higher frequency bands and high frequency type common-mode choke coil capable of the EMI attenuation of high frequency band used in the EMI Block of LED-TV SMPS. In case of high frequency type CM choke coil, it can be explained the parasitic capacitance of A type and section bobbin type winding methods among them is much smaller than the other. The first resonant frequency of the proposed CM choke coil tends to increase as the parasitic capacitance becomes small and its impedance characteristics also show improved performance as the first resonant frequency increases. In case of hybrid choke coil using rectangular copper wire, it has investigated its parasitic capacitance compared to CM choke coil of conventional toroidal type becomes small. Also it has confirmed through the experiment results that CE margin and RE margin in frequency bands 0.5MHz to 5MHz and 30MHz to 200MHz are respectively 10dB and 15dB greater than that of conventional type in case of one stage EMI filter structure adopting hybrid choke coil compared to two stage EMI Filter structure using two of each CM choke coil used in the lower and higher frequency bands or two of CM choke coil used in only the lower frequency bands. In the future, the hybrid choke coil and CM choke coil of high frequency type show it can be practically used in not only LED/LCD-TV SMPS but also several applications such as LED Lighting, Laptop Adapter, Server Power Supply and so on.

Design of High Power Permanent Magnet Motor With Segment Rectangular Copper Wire and Closed Slot Opening on Electric Vehicles*

Design of High Power Permanent Magnet Motor With Segment Rectangular Copper Wire and Closed Slot Opening on Electric Vehicles*

Design of High Power Permanent Magnet Motor With Segment Rectangular Copper Wire and Closed Slot Opening on Electric Vehicles

Brushless permanent magnet DC motors are being manufactured and used increasingly in everything from home appliances to automobiles due to their inherent advantages. The merits of these motors could be enhanced further according to another design approach method which alters the typically used winding parts for low to medium power range motors. This paper deals with the high power brushless DC motor used for traction in a 48 V golf cart system. The stator is designed with segment rectangular copper winding to maximize output power within its limited dimensions. In the design process, the closed slot opening and slot-pole combination are investigated and compared in terms of efficiency and input current density. The developed motor obtained about 120% greater power density per volume compared to a commercial motor with round winding coils at similar efficiency and variable speed range.

Researches on transmission of TE01waves in circular waveguides in the vicinity of 25 and 35 Gc/s

The characteristics of two 50 m lengths of straight circular waveguide have been measured at 25 and 35 Gc/s. The first line was made from solid copper tube of 50 mm bore by drawing to an overall tolerance, including ovality, of ±0.03 mm. The second line was composed of helical waveguides obtained by winding rectangular copper wire on a precision mandrel and surrounding it by a sheet of plastic material reinforced with glass fibre: the bore and overall tolerances were again 50 mm and ±0.03 mm. With the two lines short-circuited at both ends, measurements were made with 0.02 microsec pulses; for favourable settings of short-circuiting piston, attenuations as low as 0.3 neper/km at 35 Gc/s and 0.6 neper/km at 25 Gc/s have been measured on both lines, these results exceeding the theoretical attenuation by only 25?40%. A third line, made of flexible helical waveguide of 50 mm bore, was bent with radius of curvature extending from 50 to 1000 m; attenuation measurements showed that the losses of the TM11 wave were 1 500 times higher than those of the TE01 wave at 35 Gc/s, and 500 times at 25 Gc/s.