1) Claim: It’s better to put more copper in the slot than the “hole” (the cooling channel).
Nope. Direct cooling as implemented in our motor designs is powerful to such an extend that the need for an outer cooling jacket has been eliminated. This component consumes a large portion of the available installation volume. By eliminating or replacing the cooling jacket, there is plenty of space left for additional “active” material: copper, wider teeth or more back-iron. Ideally all of it while expanding the air gap diameter to further increase the torque capabilities of the electric machine.
2) You fancy full integration of motor and inverter. What about the conventional arrangement with motor and inverter separated?
Sure. Sometimes the individual packaging of an applicatios preferes this layout.
Our motors are best suited for powerful applications starting from 100kW to several MWs. Where there is power, lots of amps have to be moved between motor and inverter – associated with Ohmic losses, heat and EMF. In terms of efficiency, size, weight and cost, highly integrated systems are the superior choice.
3) Do you only provide 800V-systems as showcased in your data sheets?
No. We just think this is the best option and will be the most commonly choice for powerful drives in the one to several hundreds kW region. We design drive systems for all available voltage ratings.
4) Which power modules do you use for the integrated power electronics?
SiC is a popular but still costly choice for high performance drives. We choose depending on the needs of your application. A great advantage of our electric machines is that they run on moderate fundamental frequencies. This allows for the use of established and less cost-intensive IGBT or MOSFET power modules.
5) Claim: High pressure and the need for a special pump are disadvantages of direct cooling.
Correct. We eliminated high pressure by design.
Our motors are operated with a standard cooling pump.
6) Which cooling fluid do you use?
This is our little secret.
7) Could you also design axial flux or generally concentrated winding machines with your cooling technology?
Sure, we can. If your application requires a short axial motor length or is a direct drive, this might even be the best option. However, concentrated winding machines run on significantly higher fundamental frequencies for the same power output – emphasizing the challenge of increasing AC losses in the winding. Furthermore, concentrated windings have the inherent nature of genrating a vast number of harmonics within the MMF spectrum.
Here is an exemplary comparison between a 18 slot / 16 pole concentrated winding
vs. a 48 slot / 8 pole distributed winding stator.
3-phase MMF, harmonic order
8) Your concept is a nice idea. We doubt your excellent efficiency claims for current densities up to 60 Arms/mm². Ohmic current losses go in the power of two while torque and power increase proportional in best case.
Good point! There is truth in this statement. However, highest efficiency at full load is usually not needed for most applications. Have you ever done drive cycle simulations?
WLTP for instance? It’s all about part load!
For all petrol heads: Turbocharging of internal combustion engines and the positive effect of downsizing on fuel consumption is a good analog of what can be realized with direct cooling and downsizing of electric motors.
Here is a little case study:
Torque is naturally defined as a function of current density and saturation.
Efficiency and power output strongly depend on the motors ability to cool loss power in the first place and how much AC losses increase over speed for all active components.
Let’s compare a single power dense motor (10kW/kg, max. 60A/mm²) to two “standard” motors (5,5kW/kg, 25A/mm²) of roughly double size (and double no-load losses; and double cost).