In this article, a novel form of thermal interface material (TIM), represented by three industrially manufactured pressure-sensitive adhesive (PSA) tapes with electrical insulating properties, is characterized regarding its applicability in an electric motor with air-gap winding. Firstly, the adhesion performances, in terms of the winding process, were investigated experimentally. Here, every TIM shows sufficient shear strength for the wire–TIM joints, as well as peel adhesion to the laminated iron core. Secondly, the thermal–physical properties of the TIMs are inspected experimentally via laser flash analysis (LFA) and differential scanning calorimetry (DSC). For every TIM, the value of the thermal resistance can double if the relatively smooth surface (Ra = 0.2 μm) of the adjacent layers is interchanged with a rougher one (Ra = 2.0–3.7 μm). Additionally, the TIM’s performance at the system level is examined. Therefore, a flat test section, according to the specifications of the original motor, is studied experimentally and numerically utilizing infrared (IR) thermography and the finite element method (FEM). The focus is set on the heat flow and temperature distribution in the test section under varying thermal loads, mass flow, and variety of TIMs.
Due to their electro-mechanical behaviour, electrical motors are able to generate high power densities. For a 20 kg motor based on a modified air gap winding, a mechanical load of 80kW is theoretically possible. However, the achievable power density is generally limited by the thermal loads induced by Joule heating due to the Ohmic resistances in the motor's wiring. This paper discusses the potentials of cooling channel modifications, such as the overall geometry as well as surface variations, to enhance the convective heat transfer from the solid material in the coolant with focus on motors using an air gap winding. The convective heat transfer acts as a relevant thermal resistance, which becomes critical at elevated loads, because it is lies between the wiring, acting as a heat source, and the liquid coolant, acting as heat sink. The thermal resistance of the interface material between the wiring and the stator is in the same order of magnitude as the convective heat transfer. These non-metallic materials such as foils, coatings and glues for electrical insulation and mechanical bonding are highly limited in their temperature resistance. To evaluate the behaviour of modified cooling channels and investigate novel interface materials under motor-like conditions, experimental and numerical methods are employed to determine thermo-physical properties, heat and mass transfer and finally the temperature distributions. The experimental results are discussed in comparison with numerical and analytical models and validated thereby. Because of the limited possibilities for experimental investigations within a real electrical motor, a flat test bed, based on the boundary conditions of an existing 16" wheel hub motor was developed. The Ohmic heating was realised, applying a thin sheet foil of Inconel, so that specific heat loads up to 100 kW/mK could be realised. Here, the surface temperature could be measured contact-free at a high optical resolution, using infrared thermography. The most advantageous test bed feature is the optical accessibility of cooling channels which allows the visualisation of fluid flow regimes. As results, the influence of large-scale coolant duct geometry modifications on the motor temperatures and hydraulic characteristics as well as of small-scale modifications will be presented in comparison to non-modified geometries. Also, the outcomes and capabilities of novel thermal interface materials consisting of laminated foils will be discussed and an outlook on a modified motor design to increase the thermal limits will be given.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.