Design of hairpin windings considering the transient potential distribution

Abstract

With the increasing use of novel semiconductor technologies such as SiC and GaN in inverter-fed electrical machines, the switching losses of the power electronics can be reduced. However, this leads to steeper voltage gradients, resulting in a strongly nonlinear transient potential distribution along the winding of the electrical machine. As a result, the insulation system – especially the turn-to-turn insulation – is subjected to additional voltage stress. To carry out targeted dimensioning of the insulation system, it is necessary to calculate the transient potential distribution in advance. In the design of a hairpin winding, it is possible to influence the transient potential differences by employing a method called “shifting” within the winding scheme and thus to reduce the maximum potential differences that occur. On this basis, a targeted design of winding plans with hairpins can be achieved. Here, both the transient potential differences between the conductors within a slot of the stator core and the potential differences between the conductors of different phases in the end winding region of the machine are considered. Furthermore, the voltage differences between the conductors and the stator core are determined and compared for different variants. In this way, it is possible to reduce the amount of material used in the insulation system. Finally, an advantageous winding layout plan based on reduced potential differences is compared with a reference plan.