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Advanced electrical machine manufacturing process implementation and tuning based on composite material process technologies

Final Report Summary - COTEM (Advanced electrical machine manufacturing process implementation and tuning based on composite material process technologies)

Executive Summary:
This topic aims to develop an optimized manufacturing process for the Open-Rotor demonstrator deicing system electrical machine based on organic matrix composite material processing technologies.
The overall work plan is structured into five work packages, for an initial total duration of twenty four months, where progress of both the work packages and its inter-relationship with the project can be assessed. To achieve the mentioned objectives, different steps and research activities are necessary. First of all a scientific analysis and state of the art of electrical machine manufacturing process has been investigated (in WP2). This includes detailed investigations concerning all relevant parameters and information about the production process. After, the design of the manufacturing process, based on state of art and specification of the electrical machine, in close relation to the resin selection, has be realized in WP3. The optimisation of the resin process parameters has been investigated in the next WP (WP4) in order to get the most adequate parameters to the process and all environment variables. The technology has been integrated in WP5 to manufacture a first part of the prototype of the electrical machine. ENIT has carried out the financial, administrative and technical coordination described in WP1.

Project Context and Objectives:
The SAGE2 Demonstrator developed by Labinal Power System incorporates two counter-rotating propellers, which should be deiced. In electrical motor the element that concentrates complexity is the rotor and the stator. This complexity leads to a long and expensive fabrication cycle. Indeed, whatever the system design, this electrical machine can be consider as a complex assembly of enameled winding insulated from a magnetic core by layers of fiber glass reinforced thermoset resin composite, finally encapsulated with a high dielectric thermoset resin. Therefore the product cycles increase by splitting the manufacture steps.
The project COTEM titled “Advanced electrical machine manufacturing process implementation and tuning based on composite material process technologies” and ordered by Labinal Power System, aims to develop an optimized manufacturing process for this Open-Rotor demonstrator deicing system electrical machine based on organic matrix composite material processing technologies. The different tasks designed the manufacturing process, selected the resin and optimized its process parameters, and then manufactured a first demonstrator of an electrical machine. This advanced manufacturing has been based on composite material process technologies developed at Nimitech Composites (one partner) with optimized process parameters determined at Ecole Nationale d’Ingénieurs de Tarbes (second partner).

Project Results:
Firstly ENIT and Nimitech have reported a state of art on electrical machines in order to underline the benefits and drawbacks of electrical machine manufacturing, then to reduce the product cycle by integration of the various phases of manufacturing. This integration involved the study of processes of each material constituting the electrical machine. The electric machine assembly is complex because it contains a polymer matrix as the dielectric insulation, anodized aluminum sheets as reinforcements and the interface between these two elements. Two other elements exist in this assembly, the interface between the main insulation and the magnetic core and the interphase between the main insulation and the matrix. So this global process requires taking into account aspects of adhesion and compatibility of materials and resources for a sustainable and profitable product.
Starting from the integration of innovative process technologies issued from composites in the electrical machine manufacturing, we had to specify and select impregnation resins to meet with the manufacturing process requirements but also with the application requirements. So we defined and studied the first material parameters in order to conclude on a first resin selection. For a first selection, the resin parameters necessary to take into account are resin viscosity, thermal stability, weak shrinkage, material health.
The second part of WP3 deals with two propositions of design process (Nimitech Proposal).
The first one is based on one-shot impregnation in three steps: (1) The subsets (cheeks, links, coils...) are assembled mechanically and separately, (2) then the subsets are gathered in an injection mould, (3) All the interfaces are impregnated in the same time according to a studied vacuum/pressure/temperature cycle.
The second one is based on a two-shot impregnation: (1) The subsets (cheeks, links, coils...) are impregnated and pre-cured separately in different impregnation or injection moulds, (2) The pre-cured subsets are gathered in a compaction mould, (3) The global assembly is cured under hydrostatic liquid resin pressure.

After having proposed a list of materials, based on state of art and specification of the electrical machine, physical, thermal and mechanical characterizations of polymers and interfaces were performed in order to quantify the optimization level of the resin process.
Each impregnation resin was characterized using several experimental techniques in order to methodically define its physical and chemical properties. Nevertheless, the study only focused on the techniques that are relevant regarding the final application.
This optimization work based on rheology and thermal analysis enabled to pre-select three resins in a first approach. Then we studied the material mechanical and thermal properties evolutions of the chosen cured resin during ageing in order to understand the material failure mode in their future application. We defined two ageing mediums representative of harsh environment and performed accelerated ageing tests. This experimental issue implied the exact same physical and chemical analysis techniques used for unaged resin characterizations. Only the epoxy resin after ageing tests was retained.
For a first approach, NIMITECH suggested to demonstrate the previous work package choices viability by manufacturing one test vehicles. To make this prototype, it is necessary to use tools special designed by NIMITECH. Resin Transfer molding process was studied. Reinforcement mat or woven roving was placed in the mold, which is then closed and clamped. Low-viscosity resin is pumped in under pressure, displacing the air and venting it at the edges, until the mold is filled. Vacuum inside has permitted to equally divide the resin between the sheets while it fills the mold. In order to the demonstrator magnetically work, each magnetic sheet had to be covered by a thin defined resin layer which has an insulating function. The main changes have been the integration of new insulated wire technologies (such as anodized aluminum wires or ceramic platted wires) and the assembly of magnetic material sheets to form the machinery magnetic core. The results proved that the employed technology is suitable for producing magnetic parts. Additional tests on demonstrators permitted to adjust parameters in order to vary quality and thickness of the layers. This work reached completion and led to additional studies on the concrete application (magnetic rotor). The injection process was adapted to more detailed parts and new complex tools were manufactured.

Potential Impact:
The innovation is at the center of this project. Nowadays no electrical device is manufactured by using the both composite materials and processes. This project would improve the competitiveness of the SME-Participant NIMITECH in their country and also at European level by the demonstration of its knowledge in manufacturing process technology of composite materials and its ability to bring and adapt this technology to the manufacture of electrical machine, a new market.
Beyond the success of the project COTEM, NIMITECH would launch a recruiting and training strategy to meet its needs of growth opportunities. It will continuously develop its recruitment and selection practices to increase his number of employees, contributing to the European effort to reduce the unemployment rate.
ENIT has been working since twenty years on the integration of power electronics systems in embedded systems. In power converters used on the railway traction drives or planes, integration results in compacted modules in which all the elements required to energy transformation are gathered nearest to the power chips. So COTEM project covering the different steps of innovative composite manufacturing makes ENIT improving its expertise on interfacial chemistry and mechanics to better forecast wetting, adhesion and transport properties in order to pursue research activities on multifunctional materials suitable to perform structure more integrated. Results on resin parameters optimization will be implemented through scientific papers.
This innovative technology would able to Labinal Power Systems to open new markets in harder environmental conditions by deferring the thermal limits of use and by decreasing the weight.

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