Thursday, June 13, 2024

Aluminium windings?

Copper, material typically used for the windings of conventional electric motors, is more expensive and heavier than aluminium. For this reason as well, they have started the first experimentations of aluminium windings for electric motors, expected to replace a fundamental role, that is to say generating the electromagnetic field for the rotor.
Concerning this, protagonist is the British company Ricardo, which has started developing electric motors with aluminium windings intended for small-size electric cars.
Ricardo has been developing a rare-earth magnet-free sustainable electric motor concept with aluminium stator windings, which retains the key attributes of magnet-rich motors. The goal has been to create technology which is robust, costs less than current products and reduces lifecycle impact by eliminating the use of scarce resources for example up to 12kg of rare earth metals and also high acidification materials such as copper without impacting motor function or quality.
Therefore, aluminium is no longer used just for the bars of induction motors thanks to UK-Alumotor, led by Ricardo with Aspire Engineering, Brandauer, Warwick Manufacturing Group at The University of Warwick, Phoenix Scientific Industries, and Global Technologies Racing, is a consortium of experts formed to develop a supply chain around an innovative proprietary design for an electric motor.
The consortium’s aim is to grow UK manufacturing capability and to develop the next generation of skilled engineers and technicians.
UK-Alumotor consortium has received an award from Driving Electric Revolution Challenge fund – through UK Research and Innovation – to establish a UK supply chain for electric machines: leveraging manufacturing expertise to deliver next generation sustainable electric motors.

Electric Motors Efficiency needs better copper

A new manufacturing process yields highest conductivity copper composites at bulk scale. This is a discovery of researchers at Pacific Northwest National Laboratory (PNNL): they have increased the conductivity of copper wire by about five percent. Higher conductivity means that less copper is needed for the same efficiency, which can reduce the weight and volume of various components that are expected to power our future electric vehicles.

The laboratory teamed with General Motors to test out the souped-up copper wire for use in vehicle motor components. As part of a cost-shared research project, the team validated the increased conductivity and found that it also has higher ductility-the ability to stretch farther before it breaks. In other physical properties, it behaved just like regular copper so it can be welded and subjected to other mechanical stresses with no degradation of performance. This means that no specialized manufacturing methods are necessary to assemble motors-only the new advanced PNNL copper composite.

The technology can apply to any industry that uses copper to move electrical energy, including power transmission, electronics, wireless chargers, electric motors, generators, under-sea cables, and batteries.

General Motors Research and Development engineers verified the higher conductivity copper wire can be welded, brazed, and formed in exactly the same way as conventional copper wire. This indicates seamless integration with existing motor manufacturing processes.

«To further lightweight motors, advances in materials is the new paradigm – said Darrell Herling of PNNL’s Energy Processes and Materials Division. Higher conductivity copper could be a disruptive approach to lightweighting and/or increasing efficiency for any electric motor or wireless vehicle charging sytem».

Investment for a low environmental impact battery plant in Poland

Global top player in sustainable technologies Johnson Matthey (JM), announced that its new battery materials facility in Konin, Poland, has received a combined €135 million investment from two leading development banks, in yet another boost for the commercialisation of eLNO and the electric car industry. eLNO is the portfolio of ultra-high energy density next generation cathode battery materials. These are expected to improve the performance of lithium ion batteries and help promote electric vehicle usage on a larger scale.
The production capacity in Konin will be 10,000 tonnes of eLNO per year, enough for around 100,000 fully electric vehicles. In addition, the site, which will start production in 2022, has the potential to expand tenfold through further investment. Construction of the plant began this year.
Johnson Matthey aims to create a low environmental impact battery supply chain, using renewable energy and sourcing raw materials – lithium, cobalt, nickel – from “ethical” mines.
«Construction of the new plant in Konin – said Christian Günther, Chief Executive, Battery Materials at Johnson Matthey – is a significant milestone in the commercialisation of our eLNO battery cathode materials. Supported by this funding, we plan to have eLNO in production on auto platforms by 2024, enabling the shift to electric vehicles and a cleaner, healthier world for us all».

Self-lubricating polymer bearings


In many applications, bearings and supports must work also in presence of filth, dust and chips. For this reason, they need continuous lubrication and maintenance interventions. Polymer bearings by igus are lubrication- and maintenance-free, even if the support is made of metal. Precisely for these systems with metal supports, igus has developed new iglidur J high-performance plastic bearings.
The new self-lubricating bearings with sheet metal housing allow notably decreasing maintenance costs. Moreover, this new material prevents the deposition of dirtiness and dust and this represents a considerable advantage in terms of wear and allows avoiding unforeseen machine downtimes. Igubal bearings are made through injection moulding and they are economically advantageous.
They can be mounted in few seconds to replace ball bearings in already existing standard metal housings or they can be bought with a low-cost sheet metal support. The joint is composed by the sheet metal housing and by igubal ball bearing and is directly available in stock. The plastic bearing has high resistance to wear and features a very low friction coefficient in dry operation.
Currently, igubal bearings are available in three sizes for low-cost sheet metal housings (Ø20, 25 and 30 mm) and for injection moulded housings (UC204-210).

Axalta A new epoxy resin Voltacast 3310

Axalta, a global supplier of liquid and powder coatings, launches Voltacast 3310/Voltacast H134, a new epoxy-based casting resin system that expands the Voltacast product portfolio of casting resins from Axalta’s Energy Solutions business.

Voltacast 3310 is specifically designed to offer high thermal stability in combination with high thermal conductivity for winding head encapsulation or total stator encapsulation of electric motors, like servo drives or large machine tools.

“We are always looking to expand our product portfolios and to meet the ever-evolving needs of our customers,” explains Christoph Lomoschitz, Global Product Manager for Axalta’s Energy Solutions business. “Voltacast 3310 ensures outstanding resistance to a variety of automatic transmission fluid oils used in electric vehicles, and its high thermal conductivity in combination with oil cooling of electric motors allows maximum heat dissipation.”

Voltacast 3310/Voltacast H134’s anhydride-free system can be cured at room temperature or preferably at temperatures up to 70ºC. The cured material is flame retardant, fulfilling the requirements of Underwriters Laboratories (UL) standard 94, class V0, and will shortly receive official UL recognition.
The new Voltacast 3300 range is comprised of two-component systems – an epoxy resin and a hardener. The products of the Voltacast 3300 range offer superior thermal conductivity, from 1.2 W/mK up to 1.6 W/mK, without compromising an easy and safe application, as the processing viscosities are only 2200 mPa*s to 2400mPa*s at room temperature. The new Voltacast materials are very versatile, with glass transition temperatures of 24ºC, 60ºC and 95ºC, depending on the final application requirements.

Impregnating resins for mechanical stability and insulation

Axalta’s bespoke automotive products provide electrical insulation solutions and are designed to improve the performance levels of modern electric motors. They include Voltron wire enamel, Voltatex 4200 for impregnation, and adhesive electrical steel coatings such as Voltatex 1175W and Voltatex 1075K. Axalta has been a global supplier in the manufacture of high-quality, high-performance liquid insulating systems and materials for over 70 years and it supplies its Energy Solutions range of Impregnating Resins, which provide mechanical stability and insulation for electrical motors in full electric as well as hybrid vehicles, to nearly all well-known light vehicle OEMs. Michael Glomp, Vice President of Axalta’s global Energy Solutions business, says, “The development of efficient, high-performance and reliable engines for hybrid and electric vehicles continually presents new requirements and challenges for electrical insulation materials.”

Mecflon to avoid noise and reduce friction an losses

Compared to Ptfe, Meflon is formulated to provide increased efficiency, improved wear resistance, and decreased starting torque in demanding applications of food, spa, and drinkable water segments .

25During the last ten years, the market has requested sometimes to increase the operational flexibility of cooling systems using auxiliary pumps for a better control of engine cooling and efficiency, in order to meet more stringent regulations in terms of CO2 emissions. In many cases the auxiliary pumps are driven by brushless motor, regretfully still with some limited performances in terms of pump efficiency and vibrations/noise failures,  as it has been for dishwasher application of this type of motor.
Meccanotecnica Umbra developed a material for sliding parts such as bushings to reduce the sliding friction: the solution had been the MTU Ptfe material with appropriate fillers, Mecflon.
MecflonMeflon, when compared to other grades of Ptfe, is formulated to provide increased efficiency, improved wear resistance, and decreased starting torque in demanding applications of food, spa, and drinkable water segments.  As it was for the mechanical seal of dishwasher pumps,  MTU analyzed the possibility of supplying in particular bushings and rings, made with same innovative materials to prevent sticking and noise, to Tier1s and OEs that are partially replacing the traditional pumps (equipped with mechanical seals).
The irregularities of performances in real conditions are related to the occurrence of irregular flow situations and for mechanical seal, this phenomenon is bigger, because the lubricating film between the faces is typically very small. Therefore, the effect of Mecflon also for bushings has been again the key factor for avoiding sticking and noise, as it had been for traditional low power electric pumps, provided with mechanical seals.
In  the past two years   MTU  has got relevant progress in the definition of the project for brushless motors and has overtaken the preliminary testing activity on prototypes, with sizeable advantage also in terms of wear, and not only sticking and noise, in comparison with standard materials used for mass production.
Pumps equipped with Ptfe bushings don’t present axial wear of the front flange of the bushing and show lower wear of radial surface.
However, the combined radial wear of bushings and shaft for Mecflon Y4 solutions makes significantly lower overall damage in terms of eccentricity.
Morerecently MTU has started a specific development program for application of PTFE bushing to cooling system water pump , taking into account the typical working conditions of the automotive segment (-40/140 ° C, up to 6000 rpm, high additivated coolant, continuous operation during in-house recharge of batteries of hybrid or electric vehicles).

Impact on efficiency of core materials

Materials and efficiency

No matter whether intended for a small or big household appliance, or used to drive hybrid and/or electrical cars or, moreover, applied in industrial ambits, the electric motor goes on confirming an unprecedented global growth trend.

Challenge that involves materials

Component manufacturers, producers and end users focus on this faster and faster diffusion, orienting their commitment not only to the reduction of costs but also to the optimization of performances and to the pursuit of the highest efficiency. A challenge that directly involves also the materials that constitute the core of electric cars, from the magnetic lamination to the stator pack.

Stefano Fortunati
Stefano Fortunati, Senior Technical Manager Stainless Steel & Electrical Steel Metallurgy and Manager of the Research Unit of CSM Terni.

We talked about that with Mr. Stefano Fortunati, Senior Technical Manager, Stainless Steel & Electrical Steel Metallurgy and manager of the Research Unit of CSM Terni, with specific focus on the “white good” and automotive sectors. «For several years now – explains Mr. Fortunati – efficiency has represented a key development factor, also to comply with the regulations provided on national and international scale. For this reason, the household appliance and automotive fields, as well as others, have paid ever-rising attention to the high efficiency of electric motors for a long time».
Approach, the latter, that has motivated and determined a production shift towards higher and higher quality classes.
«Including – underlines Mr. Fortunati – the producers of magnetic laminations used for the implementation of electric motor cores».

The decreasing demand for raw materials

A context that highlights, compared to the past, a decrease of the demand for less valuable raw materials (classes with very low percentage values of Silicon or similar) and of “high” thicknesses (even 0.65 mm).
The current trend is preferring, also in the “white goods” world, lamination thicknesses included between 0.5 and 0.35 mm, and steels characterized by a higher Silicon content.  «Important aspect – underlines Mr. Fortunati – is also the higher care and the control of the crystalline microstructure, besides the choice and the selection of increasingly clean/pure steels (i.e. free from second non-metal phases)».
Actually, in fact, a low level of internal cleaning and purity, combined with a distribution of defects and second phases, increases the likelihood of constraints to the movement of magnetic domains during the magnetization. This implies a rise of losses and, therefore, an efficiency decrease.

The added-value of the magnetic permeability

«The demand coming from the market – adds Mr. Fortunati – consists then in the availability of raw materials with improved characteristics, precisely to enhance efficiency. It is undoubted that, from the point of view of the material research, this aspect represents a “driving force”. However, it is not sufficient for the attainment of the targets». It is relevant also the aspect of design and engineering change the electric motor is living. From a more general point of view, in the past the only (or anyway the main) key design parameter was represented by magnetic losses, by power losses.
«The progress and the design evolution – explains Mr. Fortunati – have led in time to recognize a higher value to the parameter of the material magnetic permeability. Material that, for applications on rotary machines, must assure an easy magnetization in isotropic manner in all directions of the plan of laminations constituting the ferromagnetic core». Concerning this, from the point of view of the material crystallography, it is necessary to grant that the (crystallographic) directions of easy magnetization are homogeneously distributed in the plan.
Relying on improved crystalline texture means enhancing the magnetic permeability to achieve higher applicative efficiency.
Given that and knowing that magnetic losses, heating and power losses occur in the core magnetization, it is important also to evaluate the necessary current intensity. Succeeding in magnetizing the conductive material optimally allows using a lower quantity of it.

Materials and efficency
Manufacturing cycles of steels for electric motors.

«Moreover, also less – adds Mr. Fortunati – is the current that passes inside windings. This means reducing losses. An approach that considers not only the magnetic lamination, i.e. the ferromagnetic material inside the core and its behaviour. But also how much conductive material and the necessary current intensity to achieve the expected result».
A sign that shows and highlights the great liveliness that is permeating the design of electric motors. Of whatever typology they are (induction, synchronous, asynchronous, reluctance motors and so on).
A further guideline in the general development of motors, for both the household appliance sector, the automotive and industry in general is oriented towards the research of thinner and thinner materials.
Worth considering, then, the material resistivity element, faced choosing materials prevailingly beneficiated with Silicon but also with Aluminium or Manganese. With a limit, because increasing the widely used Silicon with values exceeding 3.5%, the material becomes too fragile, making their industrial manufacturing and their use very critical. Then, a further strategy consisted in orienting the research towards the improvement of the material surface quality and of its cleaning.
«Differentiating elements – underlines Mr. Fortunati – that however lead to a sort of selection among the steel mills that today can grant the production in conformity with these requisites».

The best compromise between thickness and purity

Thickness and electric resistivity (due to the content of Silicon, Aluminium and Manganese) represent determinant factors in automotive ambit, because the law that rules magnetic losses includes the frequency multiplier factor. In other words, in alternate field, their contribution becomes very important in industrial and/or domestic ambit.
«Even more determinant – underlines Mr. Fortunati – in the automotive industry, where they usually deal with variable frequencies and high frequencies, with a reference factor for the lamination characterization that reaches 400 Hz».
We should consider that the best attainable materials by a conventional chain feature magnetic losses (measured at an operation induction of 1.5 Tesla – 50 Hz, with reference thickness of 0.35 mm) with values around 2 W/kg.
Referring instead to the characterization of similar materials, optimized for automotive applications (measured at 400 Hz), such value notably increases, up to 14-15 W/kg.
Therefore, the general trend is demanding and finding better and better solutions in terms of losses and crystalline textures, to improve their polarizability, i.e. the magnetic permeability. Dominant factor, the latter, to obtain a higher power density.
As already underlined, all seem oriented towards increasingly thin materials but marked out by worse mechanical properties, then with a potential more difficult applicability in some ambits.

The electric resistivity

The other aspect and conflicting factor is represented by the percentage of elements that increase the electric resistivity (first of all Silicon) contained in the material. «If on one hand – explains Mr. Fortunati – they prefer materials with high alloy content to improve losses, on the other hand this intrinsically hinders the opportunity of increasing the magnetic permeability».

Materials and efficency
Pilot line for magnetic lamination blank at CSM.

Today, then, it seems that research has chosen orienting the development of products with improved texture, possibly limiting the alloy content to grant a better magnetic permeability. And, meanwhile, acting on other awarding aspects to improve losses, such as steel cleaning, thickness and surface quality. «An improvement model, the latter, – notices Mr. Fortunati – more difficult to seize but leading in the future to products with better usability, for those working now at new motor projects and for the more and more challenging market requirements. Without forgetting that the trend towards the “ultra-thin” is not always positively judged by the manufacturers of cores and stator packs, owing to the sometimes critical necessary machining and more complex processes to be managed».

A glance at future trends

The current trend seems then to pursue the research of increasingly thin materials but we should consider right now the possible complications. It is then necessary to operate in parallel, for instance from the process point of view.
«Displacing for instance blanking – adds Mr. Fortunati – from mechanical systems towards solutions that adopt laser technologies, less affected by the thickness effect and that grant a minor degradation of the magnetic behaviour around the blanking/cutting areas. Meanwhile, we should imagine the manufacturing of super-thin laminations with a multilayer technology that can decrease the magnetic loss while facilitating their use».
Another element, anyway known for a long time, but really driving towards the smart use of these materials for applications such as household appliances but, especially in automotive ambit (where sizes and weights play a determinant role) is the stress control.

The role of stress control

When they design a motor, they tend in fact to obtain the best performances through the choice of the number of poles, number of teeth and so on, thus manufacturing a blank to implement the stator pack, even complex (with several cuts, slots and so on), compact and with very small sizes.

The attainment of the best efficiency of an electric motor involves several aspects. Among them, also the choice of the core materials.

«Material – adds Mr. Fortunati – that must be produced at the best possible state, without internal residual mechanical stresses that negatively influence the magnetic behaviour. It is clear that the blanking operation and, more in general, assembling processes, generate mechanical stresses and residual deformations and, actually, they deteriorate the material, with effects that become serious proportionally to the high magnetic quality of the starting material».

The use of “semi-finished” materials

The manufacturers of electric machine cores can face this aspect exploiting a stress-relieving annealing, to be carried out after the implementation of the stator pack, compacted and provided with windings.
«This process phase – explains Mr. Fortunati – is prerogative only of some companies that, instead of treating non-oriented grain material called “fully-finished”, use “semi-finished” materials. In other words, materials manufactured at lower costs and typically with relatively low percentages of Silicon, supplied not in a finished state but annealed, not decarburized and further cold-rolled, with a very low deformation level. The successive static annealing of the assembled core carried out by the user is calibrated to complete the material purification and to obtain the desired crystalline microstructure».
The analysis of this type of structure, as delivered by the steel producer, shows initial very bad magnetic specifications. Nevertheless, the stator pack producer improves the intrinsic properties through annealing (performed according to particular treatments and parameters provided for by law), which transforms the inner structure and solves the problem of residual stresses, induced by cuts and assembling operations. A process, the latter, that facilitates a calculated metallurgic process and recovers optimal magnetic characteristics. These are the peculiarities that identify “semi-finished” materials, spread especially by geographical areas.
Concerning this, Japan and United States have registered their broad diffusion for some time now, unlike what is happening in Europe. We are referring to materials that, even if considered of not excellent qualitative level, combine the advantage of a lower Silicon percentage (then better magnetic permeability), with the plus of lower cost and the solution of the criticality dictated by blanking.
«I believe that this represents an interesting field of research and development – ends Mr. Fortunati – still according to the logic of finding the best and optimal compromise able to satisfy the entire manufacturing chain, from the producer of raw materials to the motor manufacturer».

materials and efficiency
Centro Sviluppo Materiali, Terni.

Research and development activity where CSM (Centro Sviluppo Materiali) represents a qualified partner on a domestic and international scale, supporting constant innovation, process and product improvement and the attainment of higher and higher qualitative targets.

Experience and innovation at the service of materials

CSM (Centro Sviluppo Materiali) was established in 1963 as research centre of IRI in the steel industry. Today it represents the most important Italian private reality of RINA Group in the ambit of the innovation and improvement of product and process. A structure whose mission consists in developing and transferring, in industry and market at world level, the technological innovation in the strategic sector of materials and relative design, production and application technologies.
The innovation skills of CSM are based on the know-how gained in fifty years of industrial projects in metal and ceramic materials and in the integration of enabling technologies. Internet of Things, Additive Manufacturing, Big Data and Data Analytics, Augmented Reality, Collaborative Robotics and Digital Twins are some of the key words of the new context. The Centre can claim a long experience in these issues, achieved through innovation projects in the sector of materials, developed in collaboration with manufacturing companies of primary importance on a world scale.
Today CSM operates for the steel manufacturing industry and for diversified fields, such as oil and gas, aerospace, special materials and products, engineering and plant engineering, environment and energy. A strict collaboration with big, medium and small businesses, both engineering, manufacturing and service providers. All project phases, including simulations, preparations and analysis of samples and mock-ups, as well as all testing steps, take place in its own structures. Acknowledged as important pole of the European research and innovation network, CSM has always maintained a strong relation with steel partners at international level, too.
(Marcella Trapp)