Benjamin Bickel

Explicit dynamics process simulation of linear coil winding for electric drives production

Slowly but steadily, more and more electric vehicles push onto the consumer market. For a cost efficient production of electrical engines, in first-class quality and in sufficient quantity, it is indispensable to understand the process of coil winding. Thereby the prediction of the wire behavior is one of the key challenges. Therefore, a detailed model is built to investigate wire behavior during the linear winding process. The finite element based simulation tool LS-DYNA serves as explicit dynamics tool. To represent the high dynamic process of winding within this simulation, some first adaptions have to be made. This means, that dynamic influences such as rotational speed or acceleration of the coil body are definable. Within process simulation, the given boundary conditions are applied to the model. The material properties of the wire under scrutiny are validated by a tensile test and by the values out of datasheets in previous research. In order to achieve the best convergence, different contact algorithms are selected for each individual contact behavior. Furthermore, specific adjustments to the mesh are necessary to gain significant results. State of the art in coil winding is an experimental procedure, which delivers adequate process parameters and, thus, expertise in winding technology. Nevertheless, there are a lot of different, interacting parameters, which have to be optimized in terms of boundary conditions. The simulation model of winding process, in which varying parameters can be optimized pertaining to the optimal winding result, calls for extensive research in this field. The generated model enables the user not only to influence the process parameters but also to modify the geometry of a winding body. To make the simulation scientifically sound, it is validated by previous experiments and simulations

Simulation of orthocyclic windings using the linear winding technique

A continuously rising number of electric vehicle licensing is mentioned since the last few years in Germany. For a cost-efficient production of electrical engines in first-class quality and in sufficient quantity, it is indispensable to understand the process of coil winding. Thereby, the prediction of wire behavior is one of the key challenges. Therefore, a detailed model is built to investigate wire behavior during the linear winding process. The finite element based simulation tool LS-DYNA serves as explicit dynamics tool. The tool works with an explicit time integration method for time discretization. To represent the high dynamic process of winding within this simulation, dynamic influences such as rotational speed or acceleration of the coil body are definable. Within process simulation, the given boundary conditions are applied to the model. The non-linear material properties of the wire are validated under scrutiny by a tensile test and by values out of datasheets in previous research work. Simulation results of orthocyclic windings using the linear winding technique are presented within this paper. The dynamic simulation model is validated by experiments using the caster angle of the wire guide as reference parameter. The caster angel rises during the winding process of the first layer until the wire jumps to the next layer. Hence, it is possible to identify the maximum caster angle and match the simulation value against the experiment value. The travel profile of the wire guide is identified as extremely important to generate an orthocyclic winding. Another substantial part is the wire fixation respectively the geometry to support the first winding offset from winding one to winding two. Results of orthocyclic windings are simulated with and without grooves on the coil body surface and demonstrate the positive influence of grooves for an accurate orthocyclic winding picture.

Implementation of the needle winding technique for diamond coils

For the flexible production of increased efficient electric traction drives, a new winding method in terms of the indirect needle winding has been developed. It is the aim to show the full potential of the new winding technique by the manufacturing of an improved motor winding, which consists of diamond coils with twisted litz wire. Adapted devices, in particular a winding template and a needle winding tool, are investigated in several concepts and the evaluated favorites are implemented. A complete winding cell is equipped with all necessary components to demonstrate the feasibility of the modified process technology.

Active controllable and flexible winding needle an option to reduce the complexity of needle winding machines and the stress on enameled wire

State of the art needle winding technologies have one thing in common - a stiff, straight or bent winding needle. During the manufacturing process of electrical machines, the used enameled wires are exposed to deformations which decrease the insulation resistance against partial discharge and disruptive discharge. A reduced insulation resistance shortens the product lifecycle. The active controllable and flexible winding needle is able to adapt its form to the mechanical behavior of wire during any deformation and thus to wind wires more gently. In the production of electrical machines the copper filling factor in the slot is often considered key. To provide the needed space for the tools to move through the stator while distributing the windings, the winding tools have to be rather small or the inner diameter of the stator has a minimum whereat the feasibility for needle winding is still present. With the actively controllable and flexible winding needle no more extra axis and other constructions are necessary to fulfill the requirements of a small tool at maximum flexibility.

Automatisierte Herstellung von gewickelten Formspulen

Kurzfassung Die adaptive Formspulenwicklung bietet das Potenzial, dem wachsenden Bedarf an elektrischen Tranktionsantrieben mit höchster Leis-tungsdichte und Effizienz gerecht zu werden. Für die Herstellung der Spulen wurde eine Wickelanlage zur flexiblen und automatisierten Wicklung von Doppelspulen aufgebaut, Maßnahmen und Parameter zur Reduzierung von Drahtzugkraftschwankungen und Fehlwicklungen untersucht sowie ein Konzept einer Wickelschablone zur vollautomatischen Serienherstellung von Formspulen erarbeitet.

Theoretical benefits of powder-coating based insulation layers regarding copper fill factor in electric drives

Power density is a crucial requirement factor regarding high power traction drives for automotive application. As battery capacity is one of the most limiting factors regarding range of current electric vehicles, output efficiency in relation to package size is one of several levers to extend existing limitations. Within electric drives, efficiency is linked to the copper mass being implemented into the active components. The presented paper evaluates the possibility of expanding copper fill factor by the use of higher grade - and thus thinner - electric insulation materials. By using powder coatings with breakdown voltages superior to existing NMN and NKN laminates usually used as groundwall insulation system in electric drives, insulation layers can be reduced in size leaving more room for magnet wires. With regard to existing stator layouts and topologies, multiple slot cross sections are evaluated. Results show an increase of the electric copper fill factor by up to 13%, which leads to higher output or the possibility to reduce package size and mass without sacrificing output power.