I. Introduction
Groundwall insulations form a critical layer separating live wires from the lamination stack of an electric drive system. Besides this main aspect regarding their functionality, other properties and material behavior are of interest as well. As these insulation layers are also essential to an effective heat dissipation, thermal conductivity of these materials are also within focus of developers and engineers. Aramid-based slot-liners in combination with layers of Polyethylene (NMN) or Polyimides (NKN) as shown in Fig. 1 persistently form an industrial standard regarding groundwall insulation in electric machines regardless their size and power output, mostly due to excellent automation ability and low price level. Powder coatings already form an alternative to slot liners, yet economic application is restricted to high-volume production similar to thermoplastic overmoulding of laminations [1]. This type of production volume is mostly seen within small electric drives (as shown in Fig. 1) for auxiliary propulsion needs in vehicles or similar application, exceeding 100 k units per year. Using induction heating as thermal source for polymerization, overall process time is comparable to slot liner insertion [2], [3].
Protruding grundwall insulation slot-liners (white) in a random-wound stator (a); powder coated rotor (b)