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)

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