Drive system saves space and weight in electric cars

October 17, 2014 by Mr. Dr. Norbert Aschenbrenner
Siemens has developed a solution for integrating an electric car's motor and inverter in a single housing. Until now, the motor and the inverter, which converts the battery's direct current into alternating current for the motor, were two separate components. The new integrated drive unit saves space, reduces weight, and cuts costs. The solution's key feature is the use of a common cooling system for both components. This ensures that the inverter's power electronics don't get too hot despite their proximity to the electric motor, and so prevents any reduction in output or service life.

Siemens has developed a solution for integrating an electric car's motor and inverter in a single housing. Until now, the motor and the inverter, which converts the battery's direct current into alternating current for the motor, were two separate components. The new integrated drive unit saves space, reduces weight, and cuts costs. The solution's key feature is the use of a common cooling system for both components. This ensures that the inverter's power electronics don't get too hot despite their proximity to the electric motor, and so prevents any reduction in output or service life.

Because range is a decisive criterion for purchasing an electric car, automakers are always striving to reduce vehicle weight. This was also the aim of the Siemens engineers. Their idea was to integrate the inverter into the , as this would reduce weight because only a single housing would be needed. In addition, it would create six to seven liters of additional installation space, which could be used for a charging unit, for example. Integration would also eliminate the costs of wiring the motor to the inverter and fewer assembly steps would be needed to produce the vehicle.

Cooling is key

Siemens developed the integrated drive unit Sivetec MSA 3300 on the basis of a series . The engineers adapted the housing in such a way that the inverter could be integrated into the motor. One problem they faced was the heat generated by the electric motor. At high temperatures, the output of the IGBT modules - the high-performance semiconductors that convert the battery's current into alternating current - has to be limited. For this reason, inverters in . always have their own water . Another component of the overall solution is the very robust power modules featuring SkiN technology. SkiN is a bonding technology that connects the surface of the semiconductor chip without requiring bonding wire. When the thermal load fluctuates, the electrical contact between the chip and the bonding wire is a weak point of semiconductor components.

A key feature of the integrated drive unit was therefore the creation of a special cooling water system around the motor and inverter. The coolest water first flows around very thermally sensitive components such as the IGBT modules and the intermediate circuit capacitor, after which it is led into the motor's cooling jacket. The water flow system is designed in such a way that a kind of water screen is created between the inverter electronics and the motor. As a result, it thermally isolates the two units from one another.

The concept's feasibility has already been demonstrated in a lab under the typical load curves and operating conditions of an electric motor in an automobile. The industry has expressed considerable interest in Sivetec MSA 3300, and the system was recently nominated for the eCarTec Award 2014, which is the Bavarian State Award for Electric and Hybrid Mobility.

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6 comments

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EddyKilowatt
5 / 5 (9) Oct 17, 2014
Nothing against progress and refinement in EV components, but... Nissan LEAF, for one, has had the inverter -- and the battery charger and 12V converter -- integrated with the drive motor and sharing a coolant circuit since the 2013 model year. I wouldn't be surprised to find the same arrangement under the hood of other EVs, as there are all kinds of technical reasons driving designers in that direction.

But, great to see Siemens pressing forward with EV development, that can only be good for consumers and the market. What vehicles might we see this drive system in?
hgldr
5 / 5 (4) Oct 17, 2014
Eddy is correct - This isn't new technology. I've seen the electronics bolted to the motor years ago.
olsond3
not rated yet Oct 17, 2014
This is a confusing article. It talks about using a "series electric motor". That's a DC motor, which doesn't need an inverter. My 2000 Ford Ranger has a water cooled AC motor and water cooled controller, both made by Siemens. They could have bolted the two together 14 years ago. If they included the differential and get the price down below $10k they might have something. MetricMind sells a BRUSA AC motor with integrated differential for $28k. It is just absurd what these companies are charging for this stuff. How about someone in China start selling a combine Motor-differential-controller for $5k. It has to be possible.
Eikka
5 / 5 (2) Oct 17, 2014
How about someone in China start selling a combine Motor-differential-controller for $5k. It has to be possible.


Would you trust it to hold for 100k miles?

It's not that they can't make one, but it's a bit different to integrate multiple parts when you have to make sure they all perform up to the same standard. The motor controller of a chinese combo might burn out on you, and then the whole thing is just a $5,000 boat anchor.

Feyn Man
5 / 5 (3) Oct 18, 2014
"The new integrated drive unit saves space, reduces weight, and cuts costs."

How MUCH space, weight and cost?
JoeBlue
1 / 5 (2) Oct 19, 2014
Let me know when someone standardizes the controller configuration and adopts DC instead.

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