How stable is
the rotor in the
U-shaped design?


October 2021: ROTOR DESIGN

CTO Alvier Mechatronics


In combination with two shape options (U and V shape) for the rotor design, we decided on the better efficiency for our prototype. Since the rotor losses are significantly lower in the U-shape arrangement, we reduce the temperatures in the rotor and thus also in the overall system.

„Due to our high integration with the gearbox and especially due to the large thermal mass in the system, we need to cool the bearings and shaft on the gearbox side. Therefore, avoiding high temperatures is still the best measure“.

– Dagmar Münch, CONNACTIVE co-creator (Alvier Mechatronics).

Magnet weight: 1,2 kg


peak torque:

  • Speed = 9000 rpm 
  • Torque = 190 Nm 
  • Current = 600 Arms 
  • Efficiency = 95,21 % 
  • PRotoriron = 653 W 
  • PMag = 2270 W

peak power:

  • Speed = 26000 rpm
  • Torque = 57 Nm 
  • Current = 497 Arms 
  • Efficiency = 88,24 %
  • PRotoriron = 3062 W 
  • PMag = 7984 W

nominal torque:

  • Speed = 14000 rpm
  • Torque = 80 Nm 
  • Current = 340 Arms 
  • Efficiency = 95,39 %
  • PRotoriron = 726 W 
  • PMag = 1350 W

nominal power:

  • Speed = 26000 rpm 
  • Torque = 43 Nm 
  • Current = 440 Arms 
  • Efficiency = 87,51 %
  • PRotoriron = 2618 W 
  • PMag = 6106 W

Magnet weight: 1,33 kg


peak torque:

  • Speed = 9000 rpm
  • Torque = 190 Nm
  • Current = 600 Arms 
  • Efficiency = 95,65 % 
  • PRotoriron = 774 W 
  • PMag = 1354 W

peak power:

  • Speed = 26000 rpm
  • Torque = 57 Nm
  • Current = 470 Arms
  • Efficiency = 91,46 %
  • PRotoriron = 2835 W 
  • PMag = 3374 W

nominal torque:

  • Speed = 14000 rpm
  • Torque = 80 Nm 
  • Current = 340 Arms 
  • Efficiency = 95,56 %
  • PRotoriron = 833 W 
  • PMag = 826 W

nominal power:

  • Speed = 26000 rpm 
  • Torque = 43 Nm 
  • Current = 393 Arms 
  • Efficiency = 91,57 %
  • PRotoriron = 2192 W 
  • PMag = 2165 W

What about the mechanical stability of the rotor in the U-design?

We have first simply examined this question statically in a simulation - and we see a risk above the expected worst case (26,000 rpm and 135 °C). Therefore, we will further deepen these investigations and essentially concentrate on the investigation of the main operating points.

Because one thing is clear: our ambition is to consciously take risks and gain experience in early prototypes in order to push the limits of what is technically feasible.


Can you help us? What are your findings?




October 2021: STATOR DESIGN


We are close to finalizing the design.

We are securing our development with a whole series of investigations.


Here are a few details about one of our investigations of the stators:

  • We use SMC (Soft Magnetic Composites) because we are developing a high-frequency motor here. These stators are compacted and then heat treated.
  • With an axial length of 90 mm and an outer diameter of 280 mm, these cannot be manufactured from one part, but must be assembled from several individual parts.
  • At the moment we are assuming 60° segments with an axial length of 15 mm, so we end up with 6 rows of 6 ring segments each. These are to be glued together.


What influence does this bonded joint have on the electromagnetic design?


For this purpose, we conducted an experiment:

  • We have built and wrapped a stator ring.
  • Three gaps (#0, #1 and #23) had 23 turns each and their magnetic coupling [M/√(L1L2) * 100] was measured using RLC meter
  • There is a glue joint between gap #0 and #23 and no glue joint between gap #0 and #1. 
  • This is a non-invasive method by which effect of glue gap can be measured. 


  • There is a reduction as expected but it does not look of sizeable effect at a frequency of 100 kHz. 
  • Also, the flux in actual motor is radial (parallel to this gap) and would further reduce effect on the performance.


September 2021: DESIGN




We also have to cool our highly efficient high-speed motor.

The simulations show that we have to expect losses of around 5 kW in the stator including windings at the high-speed operating point.

We also want to solve this challenge in a very compact way, deviating from classical approaches: We will use 3D printed heat sinks from our partner IQ Evolution. These heat sinks are extremely compact and have an extremely high cooling capacity.



  • Stator: Somaloy 130i 5P
  • Tooth tips: Somaloy 130i 5P
  • Coils: Copper
  • Potting: Elan-tron MC4260 W4260
  • With lambda: 0,65 W/(m*K)
  • Housing: Aluminum
  • Cooling plate/rods: Stainless steel

Thermal loads at operating point: High Speed

  • Stator loss: 2.99 kW
  • Winding loss: 2.06 kW
  • Constant cooling only on the inside of both cold plates and bars: 65°C
  • Contacts: bonded


On the basis of our CONNACTIVE engineering expertise we started our new project „from 48 V to 400 V“. As Cooperation speeds up Innovation we plan to realize this until end of the year.


Our big milestones are: 

  1. End of August Req-Freeze
  2. Beginning of September: Freeze EM-Design
  3. End of September: Design Freeze
  4. Beginning of November: Start Prototyping
  5. Mid of December: 1st Prototype
  6. Test bench design validation: Q1 2022


Our co-creative approach:

We do not claim that all requirements on module or component level have to be defined first. A large part of our 200 requirements are at system level. We do not develop sequentially and in silos but with all fractions in parallel. Refinement requirements and thus test cases are added almost daily in a coordinated process and allow us a very good detailed system description and at the same time a targeted test specification. 




Perfectly in time to our milestone planning we succeeded to finish the requirement definition and accomplished our EM design.

The outcome: The future 400 V motor is designed to be electromagnetic with the relevant performance criteria: 

Hard facts: Overview motor data

Axial length: 90 mm
Outer diameter: 280 mm

We take advantage of the geometric freedom of the SMC stator and use a back core overhang, which gives us some efficiency advantages in the design. In order to be able to produce the axial length of 90 mm from SMC, we segment the stator. These parts are then glued together. The tests show that this does not result in significant losses. For this high-frequency application - fundamental frequency approx. 5 kHz - Somaloy 130i 5P is the preferred material. It is a 100 mesh powder, so the eddy current losses - which are known to predominate in this frequency range - are very low.

Of course, we will still optimise a little in detail and in the WLTP operating range, but a very good starting point has been reached. We will keep you up to date!



High speed, high frequency, high power density: join our way to 400 V.

We just started the development of our high speed solution and invite you to join the agile process
with our co-creative experts working at eye level to reach the key requirements:


// MAX-Power: 160kW

// MAX-Torque: 190 Nm

// Nominal  Power: 120 kW

// Nominal Torque: 80 Nm

// Max RPM Motor: 26.000 rpm

// Gear reduction: 25:1


Connactive started 2019 with its mission statement: Cooperation speeds up Innovation. That’s why in our projects companies from all different sectors and disciplines work together under this motto to achieve exceptional results.

And we were reaping success, as our innovative Dual Drive System with highly integrated electronics and the new powersplit planetary gearset and matching RX II unit impressively demonstrate.

Within an extremely short period of time, we thus achieved with our key drivers – design, digital twin simulations and system integration – something which other specialists take years to do: we developed a new generation of electric drive systems, from blueprint to seriesproduction standard prototype.

Director Automotive Business Unit

Uwe Rahn

“Today, technical and logistical challenges are too difficult to be won on ones own. This is why we believe in long term partnerships with our customers and our suppliers. We cultivate these relationships in professional networks like CONNACTIVE or our own Automotive Executive Community.”

Managing Director, Koepfer Engineering Gmbh

Hubert Kaltenbrunner

“Equipped with state-of-the-art calculation tools and many years of experience in the development of high-precision gear components, KOEPFER Engineering GmbH finds solutions for the special challenges of efficiency and NVH restraint in the field of e-mobility.”

CEO Pre-Switch, inc.

Bruce T. Renouard

“The leaders at CONNACTIVE understand the system level efficiency benefits of using Pre-Switch’s AI to switch e-mobility inverters at 100kHz. Our strengths of increasing drivetrain efficiency, shrinking system size/weight and supporting an unconventionally high RPM motor is paramount to the success of this new project. CONNACTIVE’S goal to channel collaboration efforts from pioneering companies will undoubtedly accelerate e-mobility and breakthrough industry barriers based on status quo. We look forward to working with their other industry leaders to firmly deliver on what is possible.”

Director of Global Business Development - Customization Technologies, Höganäs

Deniz Yigit

“It’s essential for electrical engines to become more powerful and efficient to allow electric vehicles to fulfil their vast potential, and this can be done by using AM-enabled technology and dedicated material solutions that take technology to the next level. Höganäs AB (CT) and Alvier Mechatronics have joined the CONNACTIVE project, which is dedicated to achieving high speed, high frequency and power density eDrive solutions. This cross-company collaboration will leverage the different areas of expertise of each member, and the results will drive the evolution of the modern electric engines.”

Vice President Business Development Automotive

Mustafa Dinc

"With the Eco partners VISHAY takes part in the developments from the initial stages during the concept phase and offers cost- and performance-optimized solutions."

CEO and founder of Foxy Power

Christopher Rocneanu

“The key challenges in power electronics are improving efficiency, reducing losses, and dissipating heat. Foxy Power has a set of technology which can be potentially combined to tackle those challenges and letting each technology work to its best potential to improve the overall system is key to us, Alvier Mechatronics and its partners.”

CEO and founder of IQ evolution GmbH

Dr. Thomas Ebert

„Especially in EV and Aviation applications light weight as well as small dimensions and volume are key to increase battery range and reduce overall system cost. By using stainless steel powder, we can reduce wall thicknesses to 150µm which is significant for the thermal performance of our microcoolers. This project will give all partners the opportunity to bring in their expertise while the collaboration targets to get the best total system.”

Check whether your requirements are also met in this eDrive.

If not, contact us.