AMCs: Driving energy efficiency in motors

4th November 2021
Beatrice O'Flaherty

With increasing pressure placed on engineers and manufacturers, there is an overriding urgency to improve the sustainability of their products while also meeting stringent cost and performance requirements. Out of this has sprung a drive to improve the capability of products through material innovation, where recent electric motor developments have brought weight saving and energy efficient solutions, as Richard Thompson, Commercial Director, Alvant explains.

The IPCC report, published in August, has placed the industrial sector under greater scrutiny, escalating the need to make products lighter and develop efficient electric sources of power, reducing fuel consumption and emissions. Now, thanks to emerging innovative material and manufacturing solutions, there is a means to achieve some of these high-level targets whilst increasing product capabilities, such as improved efficiency and power density (kW/kg).

Rotor sleeve solution

One area of interest is a solution harnessing Alvant’s low loss rotor technology which improves the performance of permanent magnet radial flux motors. Electric motors typically require either a magnet retention system including a mechanical rotor sleeve, which generate unwanted eddy currents and/or acts a thermal insulator depending on material. Alternatively, slotted steel laminates are used limiting the proximity of the magnets to the stator.  This can lead to increasing losses and increased temperatures, reducing the overall efficiency and limiting the power of the electric machine. In addition, manufacturing and assembly costs can be high with the use of carbon fibre composites, adhesives and heat-shrink metallic sleeves.Typical rotor sleeve materials include stainless steel, titanium, Inconel and carbon fibre composite, all of which can add to the detrimental impact on the effectiveness of the machine. Alvant, a specialist in AMCs (aluminium matrix composites) – a class of metal matrix composite (MMC), has eyed a significant opportunity through its development of core technology that retains surface-mounted magnets which minimises the magnetic bridge element of an interior magnet motor.

Alvant’s own patented process, known as Advanced Liquid Pressure Forming (ALPF), sees the company’s technology and know-how bring together aluminium with a high-functioning fibre, to create AlXal an aluminium composite that provides an opportunity to significantly reduce component mass, improve performance and increase efficiency of the world’s most demanding products.

AMC capabilities

AMCs are a family of materials whose properties can be tailored through matrix and reinforcement selection. Alvant’s current material development effort is focused on AlXal (pronounced Al-Zal), the continuous fibre AMC material, the metal equivalent of Carbon Fibre Reinforced Plastic (CFRP). As an ultra-low-density material, it has compelling mechanical properties, and is well-matched to rotor sleeve applications owing to its preferential electrical and thermal conductivity for electric motors. It offers high strength and stiffness up to 350°C, a lower magnet operating temperature compared to carbon composite sleeves and enhanced fatigue performance. AMCs are also lightweight – more than 50 per cent lighter than steel and up to 40 per cent lighter than titanium – making the material an exceptional proposition for design engineers and manufacturers who are tasked with finding alternative weight-saving and energy-efficient solutions.

A circular approach

The entire product life cycle and the ability to reuse are now very much key factors in design development, as designers must increasingly incorporate ‘whole life cost’ into design. There is now a better understanding of materials such as carbon composites and polymer composites, as they are made of two or more materials with distinct phases such as a matrix and fillers, which are precisely combined within the composites, and therefore not deemed worthwhile to separate them in order to recycle. Not so AMCs, which offer an increased opportunity to recycle. They are considered more sustainable thanks to the ability to separate the fibres from the aluminium at the end-of-life stage, therefore providing low life-cycle costs.

With sustainability now at the heart of every business’ agenda, AMCs offer manufacturers and engineers the opportunity for a step change in performance to meet ever-tightening market legislation. During what is the growth stages of an age of New Materials, now is the time for the industry to stop relying on traditional technologies and embrace change.

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