Peer Stenzel

Innovative needle winding method using curved wire guide in order to significantly increase the copper fill factor

The increase of the copper fill factor is an essential production goal in stator winding technology in order to increase the degree of efficiency and the power density of electrical machines. Orthocyclic winding patterns allow the highest packing density. Currently for round-wire-windings there are only systems available on the market that facilitate random windings, which leads to a decrease of the fill factor. Therefore this paper introduces a concept allowing high fill factors for distributed windings by using the needle winding technology.

Influence of different impregnation methods and resins on thermal behavior and lifetime of electrical stators

The relationship between impregnation process and winding temperature has not been analyzed in detail yet. Therefore, one purpose of this paper is to investigate the correlation between impregnation process, resin absorption, applied resin, and thermal behavior. Apart from thermal behavior, it has to be ensured that the lifetime of the manufactured electrical machines still meets industrial specifications. The lifetime is primarily affected by the quality of the insulation system. So the second purpose of this paper is to investigate the influence of the named aspects on the lifetime of an electrical machine.

Experimental investigations of the needle winding technology regarding the influence of the wire guide geometry on the tensile wire force

The needle winding technology is distinguished by a high degree of flexibility and automation. However, high wire tension due to the tensile winding force proves to be detrimental. Wire stress can cause an increase of the ohmic winding resistance, thus leading to a decrease of the degree of efficiency and a reduction of the continuous power of an electric machine. A closed-loop-control of the tensile winding force is basically possible, however, the influence of the wire guide on the tensile force cannot be included due to the possible measuring positions. In order to use the automation potential of the needle winding technology it has to be ensured that quality and power of the winding products are not degraded. Therefore the influence of the tensile winding force on ohmic resistance as well as the influence of the geometry of the wire guide on the tensile force has to be known. However, such investigations have either not been conducted so far or are currently not publicly accessible. The winding parameters are usually based on experience, which is not sufficient for high power density applications. Therefore, in this paper experimental investigations are presented concerning the above mentioned topics and potentials for improvement are identified.

Torque ripple reduction in permanent magnet synchronous machines with concentrated windings and pre-wound coils

Ideally, improvements of the manufacturing process do not cause deteriorations of the product characteristics. Pre-wound coils for electrical machines with concentrated windings are such an improvement. The easiest way to enable the assembling of pre-wound coils is simply the absence of pole shoes. This paper discusses the absence of pole shoes based on a sample machine. The focus lies on changes of cogging, avg. nominal and peak torque and the occurring torque ripple. Furthermore, different technologies as a variation of the tooth thickness, skewing, magnetic slot wedges and plug-in connections are investigated to compensate deteriorations of torque behavior. In addition, the effects of these technologies on the manufacturing process of a stator are discussed.

Optimization algorithms for maximizing the slot filling factor of technically feasible slot geometries and winding layouts

High power density and efficiency are key factors for automotive traction machines. One possible way to reach these goals is to increase the slot filling factor. As yet, most research has either been focused on optimizing the slot geometry with a given magnet wire diameter or on finding the optimal diameter for a given geometry. Oftentimes the submitted results lead either to a magnetically suboptimal stator geometry or the suggested winding pattern and geometries are not producible. The introduction of the needle winding technology, as an alternative to the insertion technology for the manufacturing of stators of automotive traction machines, enabled a defined wire placement in the slot. To use the full benefit of this advantage an optimal and producible winding layout is necessary. Therefore, in this article new optimization algorithms are proposed and compared to algorithms found in literature with regard to reachable slot filling factors and producibility. In a case study, the best performing algorithm was used to obtain an optimal combination of wire diameter and slot geometry to maximize the filling factor. With the proposed algorithm feasible winding patterns and slot geometries with an optimized filling factor can be obtained.

Highly flexible connection unit for electrical machines with concentrated windings

This paper discusses a highly flexible connection unit for electrical machines with concentrated windings. First, some general restrictions and requirements on connection units are identified. Then a suitable joining technology for the connection unit is investigated. Afterwards, the design of the highly flexible connection unit is introduced and applied to a sample machine.

Needle winding for distributed round-wire-windings without the use of insulation disks

Automotive traction drives require primarily high degrees of efficiency and high power densities. Therefore one main goal in the production of electric traction drives is the minimization of the end windings. End windings are necessary, however, they do not add to the power transformation and in addition they increase the space and the copper losses. In the serial production of distributed round-wire-windings the insertion technology is mainly used. An alternative to this production method is the needle winding technology. In the recent past several concepts for distributed windings have been developed and published using so called “end disks” or “insulation disks” [1], [2], [3], [4]. Insulation disks offer advantages concerning process automation, however, they lead to a considerable increase of the height of the end windings. In order to make the needle winding technology applicable for automotive traction applications this paper presents a new concept for distributed windings without the use of insulation disks.

Impact of the needle winding technology on the operational behavior of an asynchronous machine

Distributed round-wire windings are usually manufactured using the insertion technology. If the needle winding technology is applied instead the end windings have to be conducted in a three-layer axial arrangement. This leads to differing coil lengths and thus to a phase asymmetry which is much more distinct than the one resulting from the insertion technology. In addition, it is possible that the first phase exhibits a higher end winding leakage inductance than the other phases if the distance between the first phase and the front end side of the stator core is too short. In this case the magnetic flux lines of the end windings partially close across the stator core producing an increase of the end winding leakage inductance. Therefore, in this paper the impact of the needle winding technology on the operational behavior of an asynchronous machine is investigated. For this purpose a needle wound electrical machine with three-layer end windings is compared to an electrical machine with very symmetric windings built up using manual insertion. By the use of the no load and blocked rotor test as well as a static stator measurement the machine parameters are determined and the impact of the phase asymmetry is investigated. In addition, load measurements are conducted in order to quantify the impact of the production related differences.