In conformity with consumers’ demands and environmental protection requirements, vehicle manufacturers look for increasingly small and light components, to increase vehicles’ autonomy for each recharge. Consequently, transmission bearings, especially in electric motors, are subjected to higher and higher speed and performance requisites.
The previous generation of very high-speed ball bearings for EV motors was characterized by speeds of 1.4 million dmN and significant improvements in the cage and in the technology to increase their mechanical strength. With the third generation, NSK has aligned the solution to the demand for bearings able to reach even higher speeds. Besides the rotation at 1.8 million dmN (with the 28.5% increment), the new bearing is provided with a cage with optimized topology (OT). This process has allowed optimizing the material distribution inside the design space, with the target of obtaining the highest product performances. In the new bearing, the topology optimization has allowed maximising strength and minimizing weight, eliminating the parts that do not contribute in the strength and stiffness of the cage, so obtaining the optimal cage shape for high-speed rotation. The cage, made with a new resin with high stiffness degree, was designed in very short times exploiting a forefront simulation technology to assess its performances and production modalities.
Moreover, NSK lubricates these bearings with a purposely developed grease that reduces the resistance at high speeds and the consequent heat generation, extending the duration of grease and bearing and decreasing the seizure risk.
Super-fast ball bearing for electric motors
Transmissions: electric cars with gearbox?
The gearbox absence is a characteristic of the vast majority of electric cars, which rely on a system of direct transmission and reducer, turning to the torque of the electric motor.
This is not the opinion of Bosch, believing that with the gearbox EV A vehicles can improve the car performances, especially if a CVT transmission system is at stake.
It is a technology that continuously varies the ratio while driving to achieve the best motor performance in relation to power and torque.
The new transmission is under Bosch experimentation on board of a Volkswagen e-Golf: a slightly modified version of the standard CVT, called CVT4EV.
It seems there is an improvement of the car acceleration and speed and, besides, the transmission enables motors to be less powerful than those used currently; consequently, also battery packs can be reduced, so decreasing weights in favour of the general efficiency.
“CVT4EV – explained Gert-Jan van Spijk, head of CVT programme by Bosch Transmission Technology – widens the array of electric cars».
Electrical compressors with integrated power electronics
A high-speed electric motor and integrated power-electronics allow achieving competitive manufacturing costs. This is highlighted by a recent important job order in the electro-mobility field, where Bosch is protagonist with the supply of fuel-cell components to cellcentric, a 50% joint venture between Daimler Truck and Volvo Group. It is a long-term contract for the supply of electric compressors with integrated power electronics to share in making transports sustainable and neutral for climate by 2050. The component will be part of the fuel cell system of cellcentric for heavy commercial vehicles and for stationary applications. The use of a fuel cell propulsion system that exploits hydrogen allows making the vehicle neutral for climate. The electric compressor supplies the necessary quantity of filtered air and it is therefore one of the fundamental components of the system.
«Bosch – explained Uwe Gackstatter, President of the division Bosch Powertrain Solutions – offers the compressor in two power classes: 20 and 30 kW. The 30-kW size is calibrated for voltages from 450 to 850 volt, whereas the 20-kW one is suitable for 250-450-volt or 450-850-volt voltages. The compressor turbine reaches speeds of over 100,000 rpm. The combination of high-speed electric motor with integrated power electronics allows achieving competitive manufacturing costs. Moreover, silicon carbide semiconductors of silicon carbide used in power electronics by Bosch make this component highly efficient, precisely the characteristics cellcentric was looking for».
Production of electric motors: new automation frontiers
Two companies that have shaken their hands to improve the manufacturing world of electric motors are Bosch Rexroth, multinational specialized in industrial automation and motion of mobile operating machines, and McService, Modena design company the operates in the engineering sector and is specialized in the gearmotor, especially in the electric motor ambit. In recent years, it has collaborated with companies that produce electric motors and it is structuring technological solutions able to improve and to objectify manufacturing processes and, in this direction, about ten years ago, the meeting with Bosch Rexroth took place.
Let us come to innovation: the automated motor-closing machine ideated by the two companies has displaced processes from manual to automatic. Many assembling phases of the electric motor were carried out manually on a work bench, now instead all components are loaded by the machine and this proceeds to executing assemblies.
Such operations occur in what is called “hidden time”, that is to say a process that was previously carried out by the operator whereas now it is carried out by the machine in the same identical tine in which the operator performs another operation.
The machine can assess the work progress inside the job order (it knows whether it is at the beginning, half or end of the manufacturing batch) and inside each single production batch it knows whether each single motor has been closed correctly or if there are some anomalies. This machine can shorten the assembling times of electric motors, objectivating and making assembling data usable, due to linear axes and to the PLC intelligence that makes everything programmable and flexible.
The role of Insulating Materials in the electric motor
The last meeting of Electric Motors Talks that have accompanied us in the last 3 months with interesting technical insights dealt, as primary subject, with winding Insulating Materials. The enthusiasm of Sebastian Kuester, CEO Quickfairs, was perceivable and involving: he connected from Pordenone, precisely where in September it will be held Coiltech exhibition that– finally – will open the doors to attending visitors.
The webinar was chaired by Professor Andrea Cavallini, from the Department of Engineering, Electric Energy and Information “Guglielmo Marconi of University of Bologna.
The morning session
Among speakers, the ice was broken by Stefan Hilbenz & Heinz von der Heide from Synflex company that proposes a complete range di insulation materials for any electrical insulation system. In fact, the core competence of SynFlex lies in the development, manufacturing and distribution of conducting and insulating products for electrical insulation systems of electrical motors, transformers and generators. With their speech “Thermal evaluation of electrical insulating materials”, the two experts have explained in-depth the temperature class rating multi-layer Laminates and the three possible evaluation criteria it is possible to adopt. «DIN EN 60626-3 can be called into question if materials are described in this standard. And after, an individual material or component of a laminate has been classified in a temperature class based on a long-term test. Third, a component of the laminate has been approved by means of UL FTA long-term test with a minimum thickness in an UL system».
The following speech was up to James Bonnett, Program Leader E-mobility di Victrex who described how new magnet wire with peek polymer coating can improve electric powertrain performance. Spotlights then cast on peek polymers and their unique combination of properties able to provide the solutions for the future electric architecture. «With the primary levers for EOMs being range/cost, charging speed and driving experience, the right insulation solution can offer several benefits». Among these, there are greater power ad energy density EV technologies, Improved efficiency through better thermal management and higher voltage powertrains/e-motors. Whereas, in the recharge infrastructure ambit, advantages are faster vehicle charging speeds, faster “Silicon Carbide”, switching technology.
Moreover, James Bonett explained that because more efficient power electronics technology is reducing rise times of inverter pulses, the insulation requirement on the wires is increasing. Besides, most critical point for the insulation to handle these stresses is in distributed wound machine, where Phase-Phase values of between conductors are most important. Among the successes shown, there is also the improvement of the motor efficiency modelled over WLTC-Class 3b drive cycle using Jaguar iPace.
Afterwards, Elantas company with Nils Bergemann who highlighted the Thermal management of impregnated stators, showing the computer modelling approach with practical results.
«The quality of the impregnation is most important. Air is the enemy: the best heat transfer is obtained if the slots are filled completely after impregnation. The best impregnation results can only be achieved if the resin can be applied easily. Enhanced thermal conductivity of impregnation resins is realized by the addition of inorganic fillers. Such fillers influence the impregnating properties of the resin».
Furthermore, the German expert explained how to isolate the effect on thermal management
Paying attention to the comparison of standard resin and resin with increased thermal conductivity on standard object. The company in brief: Elantas is top player manufacturer of insulating and protective material and it develops and produces wire enamels, impregnating resins and varnishes, casting and potting resins, electronic coatings, adhesives, flexible electrical insulation materials, special coatings, products for printed electronics as well as a wide range of tooling and composite materials. Nils Bergemann also detailed the relevance of investigated parameters, comparing filling factors with the thermal conductivity. «Filling factor is most sensitive parameter for heat dissipation. Lower thermal conductivity can be compensated by higher filling factor».
The following company was Axalta, renowned for coating systems, in the specific case it widely and exhaustively highlighted the solution Voltatex® 4224 – Impregnating Resin with high thermal conductivity. Lars-Goeran Rohrbeck talked about tasks of impregnating resins in electrical machines, highlighting reliable protection of the winding against stress of influences like heat, mechanical and electrical.
Besides, highest possible filling of all cavities within the copper wire coil offers better heat dissipation because of difference in thermal conductivity with air and commonly used impregnating resins.
Among the criticalities stressed by experts, there is the heat flow preferably within copper and impregnating resin in end windings and notches is bottle neck for heat transition to ambient air/cooling system and laminated core.
The afternoon session
The afternoon session started with Christoph Herold – from the company Von Roll Institute for High Voltage Insulation who spoke of Testing of electrical Insulation for High Performance Motors.
The speech started by focusing on the challenges in automotive sector, come increase charging speed, reduce losses, reduce weight, higher power and increased efficiency.
«Choice of insulation is dependent on required design e process».
In the speech, much room was also given to Partial Discharges (PD) and relative detection methods come electromagnetically or galvanically coupled PD measurements, optical detection, acoustic detection and ozone detection. «PD inception-voltages increase more or less linearly in relation to thickness».
Axalta Coating Systems company was protagonist again, with a different speaker:
Alexander Litinsky talked about Polyesterimide Resins for Medium and High Voltage Applications, highlighting medium and high voltage, the situation with Epoxy-Anydrides and polyester impregnating resins. Room was also given to the thermal evaluation and classification of insulation system used in rotating machines and the insulation system evaluation.
The webinar, but also the entire cycle of meetings, was ended by Demak with its manager Alberto Menozzi who spoke of EV/HEV Motors Potting with high performance resin systems.
The speech was aimed at illustrating the company’s forefront R&D ambit and testing laboratories of the potting laboratory and at explaining the targets of the resin encapsulation such as the reduction of the total weight, lower vibration and noise, thermal shock resistance, chemical and humidity resistance and size reduction with increased power and integration density.
«Stator impregnation is performed with coating resins applied by overheating due to poor heat dissipation, possible vibrations causing noise and winding shortcut and easier chemicals dusts pollution and humidity attack and damage of windings».
Electric motor: zoom on manufacturing
It was held the penultimate date of the cycle of meetings organized by Coiltech Electric Motor Talks, precious opportunities of technical collaboration among sector experts, able to inspire and to promote the technological forefront.
In the two technical webinars on June 23rd and 24th, the debated theme was the Manufacturing of Electric Motors for the Automotive Industry: the first day focused on staks manufacturing and the second on winding and permanent magnets.
For the first time, Sebastian Kuester, CEO of Quickfairs and Prof. Marco Villani, professor at University of L’Aquila, as well as technical director of Electric Motor Engineering, presented the event in a classroom with the attendance of enthusiastic students of the electric engineering master’s degree precisely at University of L’Aquila.
«We have chosen the topic concerning the manufacturing of electric motors for the automotive industry –Prof. Marco Villani explained- because the electric vehicle market is growing and lively interest is aroused in propulsion systems with high power density and efficiency. Several companies are investigating new solutions of electric motors with high performance. However, the design of electric motor requires the use of appropriate design procedures and innovative materials to satisfy high requirements. The motor performances are assured if the motor is manufactured and assembled correctly. Currently, processes are automated to assure the high quality of the finished product and this webinar precisely analyses the details».
Cores manufacturing
Lukasz Mierczak from Brockhaus opened the proceeding speaking of detrimental impact of manufacturing processes on stator stacks properties and performance of electric motors. The company is one of the top player manufacturers of measurement equipment for magnetic materials and he drew the attention on the link between magnetic properties and motor performance and the characterisation of soft magnetic materials. «Measurement conditions specified in the international standard IEC 60404-2 are shape of polarization J waveform should be sinusoidal, measurement temperature should be 23°C and no external stress exerted on the specimens. Epstein measurements under standard conditions are insufficient for proper power loss characterisation of magnetic materials used in automotive applications».
The expert added some details about measurements under mechanical stress and effects of manufacturing on magnetic properties of stator laminations, detailed the characteristics of his product, Brockhaus stator tester BST-M, and highlighted the most salient information: «Manufacturing processes, such as stamping, welding and housing have a detrimental impact on magnetic properties of stator cores. Deterioration of magnetic properties due to manufacturing can significantly affect the efficiency of electric motors. Continuous monitoring of stators quality is necessary for assurance of expected motor performance and driving range of electric vehicles».
The company Schuler Pressen Gmbh, in the person of Markus Rover, cast the spotlights on highspeed production of traction motor stacks with bonding varnish. The company, founded in 1839 in Germany, is provider of first-rate technology and innovative system solutions for the digital transformation of forming technology. Today’s choice for serial production of traction motor cores is progressive stamping and interlocking. To achieve the highest efficiency, there are some requirements when stamping traction motor cores.
In the forming theme, the manager illustrated the various methods in relation to the different advantages and drawbacks, like the first Interlocking method, Top Dog. But limits come into view, featuring the pluses of being commonly available, and efficient, but the damage of isolation between laminations increase iron losses, challenges for joint by thinner gauge material, joining forces and pack density is limited, post -processing is necessary. «The second method Ind-die gluing has the advantages of isolation, that is undamaged, less iron than with interlocking and integrated in stamping process.
The method 3 is In-die bonding and it’s in the raw material and has a plus about full-faced bonding that allows delicate geometries, but there is a compromise between integration in stamping process and motor requirements, bound to raw material». Finally, stamping and bonding, then the method number 4, has the advantages that separate stamping and bonding processes allow max output and ideal process control for each process.
The following speech was entrusted to Thomas Stauble from SWD, who talked about segmentation of stators, in particular segmentation pluses. The first consists in smaller diameter tolerances with segments, then less material usage, followed by independent material selection for stator and rotor and, finally, the no-straightening.
In the ambit of bonding technology, the advantages of bonding varnish are higher precision, higher stiffness, very good insulation and less vibration and noise. The manager had also the opportunity of presenting Backpaketiersystem, the solution for the mass-production of segmented stators for automotive powertrains.
The last speech of the first session was delivered by the Italian enterprise Dema, a company that ensures reliable results through the “tailor-made manufacturing system” that has magnified the advantages of both industrial and handcraft methods since 1952. Dema offers tailor-made production and inspection machines that follow the special needs, guarantee quality and high-performance standards and time goals. In order to obtain these results, DEMA develops, designs and builds internally Stacking, Joining, Inspecting and Assembling machines for rotors and stators. The two speakers from the company, Barbara Ottonello and Mauro Guido, debated Innovations for E-Powertrain Stators manufacturing.
The company is focused on development of technologies needed for the use of Backlack laminations: Backlack, T-poles (automatic production), bonding process, specific tools, T-poles winding, stacks final assembling, post processing activities and quality control.
They also spoke of perfect simulation of the production system.
Winding and PM manufacturing
The following session, held on June 24th, began with the speech by Francesco Lucchetti from Tecnomatic, who presented “Hairpin 2/3 D forming systems: new practice and progress”.
Thanks to its 46 years of experience, the company aims at being partner in design and manufacturing of turn-key system for assembly and testing of automotive components and for winding systems for stators.
Going into the detail, «the wire is first straightened and cut to size, usually followed by stripping the insulation of the wire ends. If in the following steps the trimming just before welding is not expected, the cutting to length operation is too important to get the right hairpin leg length. Some considerations worth highlighting: punch and die allow getting deterministic geometries, fast 3D bending method could have less repeatability and contemporary forming is very cheaper». In the last years, the need for high power density and efficiency has become a central concept in the green transportation sector and a special challenge for the hairpin forming machine is to improve the quality and to reduce the product cost. In order to get these results, challenges consist in thinking and designing new practices and achieve innovation.
As interesting was the speech by Paolo Caviggioli from BTSR, who focused his speech on “Intelligent devices for the online control of wire and yarn tension”. The company develops two families of device: CWF and Mini Mega giga TRON. Trump card is total quality control, from wire feeding bobbin to final coil.
Based on the new concept of “dual drive system”, the device designed and implemented by BTSR International can grant the perfect combination between the feeding control and the accumulation control. A high technological multi-patented system that leads to a fully new wire tension control modality, differing from the already known and more conventional ones, it allows reaching efficiency and quality process.
Robert Goehring, MARPOSS GmbH, instead analysed thoroughly how to detect latent defects in e-motor testing. The comparison between standard tests and partial discharge tests occurred at the beginning of the report, highlighting e-Motor testing purposes prevent failure by evaluating, and e-motor critical reliability test, but also on limits of AC/DC dielectric strength test (Hi-Pot) & Surge Standard Tests. The manager is clear: «Standard tests are not enough to identify all defects. Many defects produce only partial discharge and can be identified only with partial discharge measurements that should be performed in addition to standard tests».
The protagonists of the final speech were PM rotors in situ magnetization for Powertrain motors. Concerning this, Federico Russo from Electro-physical Laboratory was present.
PM Brushless motors are the first choice for electric and hybrid vehicles. One part of the motor is the inductor, which provides the magnetic field by means of series of permanent magnets. Until a couple of years ago, motor producers used to magnetize magnets, and the effect of hot glue on pre-magnetized magnets quality all made it necessary to magnetize the entire rotors after assembly. It is in-situ magnetization. It comprises the magnetization, quality control, and handling automation. Here, the most recent development on EV PM rotor magnetization is described, with focus on design, development, MP equipment, and related automation system production.
(by Lara Morandotti)
Innovative semiconductors for electric mobility
The increase of OEM partnerships in the ambit of the electric vehicle production is the tangible proof of the market’s neat direction. News, on the other hand, unceasingly confirm several manufacturers’ conversion will towards a global electric offer.
Concerning this, one of the latest news regards the Swiss STMicroelectronics that has undertaken a collaboration in the e-mobility sector with Renault Group and the British Arrival developer. With Renault, the collaboration focus is the development, the production and the supply of STMicroelectronics products and associated packaging solutions for the power electronics of Renault Group’s electric vehicles. The brand target is reaching higher ranges, lower battery costs and improvements in recharge processes.
In its turn, STMicroelectronics is releasing components based on innovative materials like silicon carbide and gallium nitride: if silicon is replaced by silicon carbide in semiconductors, switching times decrease and the operation at higher temperatures is possible, too.
«ST is at the forefront of the development of advanced power semiconductors enabling the mobility industry to move to electrified platforms. With higher-efficiency products and solutions based on advanced materials such as Silicon Carbide and Gallium Nitride, we will support Renault Group’s strategy for its next generation of electric and hybrid platforms,” said Jean-Marc Chery, President and Chief Executive Officer, STMicroelectronics. “ST and Renault Group share a common vision for more sustainable mobility. This partnership will be another step forward in the progressive decarbonization process initiated by the mobility industry and its supply chain».
Aerospace: solutions for tests on electric motors
One of the most critical aspects for electric or hybrid aircrafts, deemed by many people the main future means of transport, are the high safety and redundancy standards they must conform to. Concerning the certification, Easa (European Aviation Safety Agency) is working at a new specific regulatory framework for this type of aircrafts, while FAA (Federal Aviation Administration of United States) has decided adapting the certification procedures of small airplanes to eVTOL.
Therefore, this might lead to satisfy different requisites, with the possibility of having to obtain a double certification, in other words an eVTOL project developed in one of the two continents can need substantial modifications and additional validations to be compliant in the other.
For specific applications, HBK relies on solutions such as eDrive, a platform of power and data acquisition analysis for the execution of innovative tests on electric motors. eDrive consists of two components: a power analysis device and a data collection system, which detects in synchronous modality electric signals, torque, speed, temperature, acceleration, CAN bus signals and other variables.
Moreover, the possibility offered by the system of storing raw data allows the user to analyse the data in post process, using complex functions equipping the software. eDrive Testing offers then unique functions compared to standard power analysis devices and can be used also with multi-phase and multi-channel applications.
New customized EV modular platform
To support automotive startups and OEM in speeding up their course towards electric vehicles, Williams Advanced Engineering (WAE) has started a partnership with the design and development company Italdesign, to provide a solution of customized modular EV platform. It is an offer in world preview that combines the new sliding frame for WAE electric vehicles with turn-key vehicle development services signed by Italdesign.
Standing out from the other EV platforms currently on the market, EVX integrates the battery casing with elements more commonly perceived as part of the body structure. The front and rear frame structures are mounted on the carbon composite housing and shock loads can be transferred via internal reinforcements to the integral side sills.
The joint venture will support the creation of premium electric vehicles as high-performance GT, Crossover and Sedans.
Italdesign Engineering team completes then the vehicle’s architecture, adding safety systems, structures and UX devices to constitute the modular platform that will be the basis to implement various high-performance vehicles.
Microelectronics: Smart Factory project authorized by Mise
Selected by EU for the high technological impact in the ambit of the call ECSEL JU 2018, (Electronics Components and Systems for European Leadership), the project represents the bearing pillar of the European industrial strategy in the electronics field.
It is called “MADEin4”, Italian project presented by STMicroelectronics, FCA Italy, Comau, Turin Polytechnics and CNR Institute for Microelectronics and Microsystems, which aims at improving the manufacturing productivity, in conformity with the targets established by Industry 4.0 plan, by means of innovative techniques and tools that allow managing and monitoring industrial processes in real time, assuring precision and accuracy in product implementation phases.
For the implementation of this research and development project in the sector of microelectronic productions, the Minister for the Economic Development Giancarlo Giorgetti has then signed the decree that authorizes the Agreement for innovation with Lombardy and Sicily Regions.
Consequently, STMicroelectronics, FCA Italy and Comau will succeed in enhancing not only competitiveness but also efficiency of production systems in the sites of Catania, Agrate (Monza and Brianza) and Grugliasco (Turin), besides granting workers’ employment.
The agreement provides for an overall investment of over 18.7 million Euros, for which Mise allocates 5.6 million Euros in subsidized loans while about 4 million Euros derive from European funding.