Siemens Integrates Electric Car Motor/Inverter Into Single Unit

NOV 15 2014 BY MARK KANE 18

Siemens has developed a new drive motor for electric cars called the Sivetec MSA 3300, which has an integrated inverterĀ in a single housing.

According to Siemens, this will reduce weight, size (six to seven liters of additional installation space) and cost of drivetrain (integration would also eliminate the costs of wiring the motor to the inverter and fewer assembly steps would be needed to produce the vehicle).

The most important part of the new solution is use of a common cooling system for both components, because an inverter’s power electronics wouldn’t withstand too much heat from the motor.

Sadly, we don’t know the specifications of this device, nor if any carmaker is willing to buy the Siemens Sivetec MSA 3300 unit.

“Cooling is key

Siemens developed the integrated drive unit Sivetec MSA 3300 on the basis of a series electric motor. 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 electric cars. always have their own water cooling system. 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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18 Comments on "Siemens Integrates Electric Car Motor/Inverter Into Single Unit"

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Is the inverter serviceable or replacable with this setup?

And of course if the answer to your question is “no,” the downside would be a problem in either unit requires both be replace at a higher cost.

Dr. Kenneth Noisewater

Could be interesting for a motorcycle or a subcompact economy EV, but I reckon larger, more powerful EVs will want inverters that can supply bigger and/or more motors. For higher power levels, having a dedicated cooling loop and/or more physical separation from the motors would be the way to go.

Didn’t Tesla do this years ago?

In both Teslas they’re closely located, but still separate.

I’m curious about the phrase “Series Motor”. In the states that would mean a DC motor, which then would not require an “Inverter”.

Anyone have any idea what Siemens means here?

A series AC motor is built similar to a DC series motor. An AC series motor can operate on AC or DC. They are also know as Universal Motors. However they are not as efficient as most other AC motors and they can be built smaller. Most series AC motors are found in household appliance.

Uh, yeah Jesse, but large series wound motors start having too much trouble with Armature Reaction at anything much above 25hz. They are properly called AC commutator motors. This is why traction motors running directly on alternating current have been 25 hz in North America and 16 2/3 hz in places like Switzerland.

They can’t really be talking about this, because regeneration control would be difficult.

Now I have made dynamic brakes on series wound dc motors by carefully adjusting the braking resistance to the load to be decelerated, so its not absolutely impossible to do it this way, I just wonder WHY, since its much easier to do with a 4 quadrant inverter and a polyphase motor.

THere’s also the lousy brush life on AC commutator motors on anything above 25 hz.

It’s not clear what Siemens means by “series”, but it is definitely not a universal motor with brushes! There is no way anyone would go back to high maintenance commutation brushes since electronics have long ago enabled practical AC traction motors.

That was precisely my point, if you read between the lines a bit. Brushed motors have an application on Converted VW BUGS and other relatively lower powered applications, but even these would have a very difficult time on alternating current, which, & I don’t think this point has been mentioned yet, DC these days is quite easy to come by. AC commutator motors just had the advantage of using power when the only easily available power WAS AC. So all the cheap conversion kits use pulsed dc drives to efficiently regulate the dc voltage. This is almost trivially easy to do these days, whereas decades age it was more of a chore, so much so that interurban commuter trains just used an on-board transformer and an AC Commutator motor in lieu of a space-robbing motor-generator set. Its easy to say that most electric cars are powered from DC batteries. And a variable voltage off these constant voltage batteries is not that big of a deal. Therefore, there is no reason to use an AC motor. So, I don’t understand why Jesse mentioned it, unless he didn’t know you can’t use them above 25 hz, which is a non-issue with battery-electric-vehicles… Read more »

That is of course, with the exception of an AC induction machine, which gives you the advantage of:

1). Simple control
2). No Brushes.
3). No rare earths
4). Braking is as easy as motoring.

To avoid any confusion, the above paragraph was discussing AC Commutator motors which is not the same as a Tesla. This was in response to Jesse, and is a bit ‘Inside Baseball’.

Full agreement, Bill…. My comment was also directed to Jesse Gurr by reply sequence.

Apologies if miss-communicated.

The real breaktrough would be the silicon carbide IGBT that would almost be 99% efficient and much less temperature sensitive.

Kind of like the old VHS/DVD combos? If one breaks you gotta replace the whole thing? lol

This is the same approach Tesla uses on the Model S, the unit is the size of an office trash can. If something dies, they swap in a new unit and send the old one off to get fixed.


I don’t trust that company. They bought out the company I was working for and laid everyone off including me. I should have expected it from a company whose name is an anagram for “nemesis”.

Good advice. Don’t trust any company unless you own it. The primary purpose for every company is to make money if they cease to make a profit they go the way of the Dodo bird. Always make sure that you make your employer money or you to will go the way of the Dodo bird.

It looks like there could be an output on each end of the unit?

Is there a differential in this unit, as well?

GM has also integrated the inverter/controller in the gen 2 Volt, and it is definitely the way to go for cost reduction since it eliminates the high current motor cables and simplifies cooling system design.

Servicing shouldn’t be an issue if it is designed right since top cover could be removed to access the inverter, which then could be unbolted from the main casting. For example, the gen 2 volt bus bars are bolted directly to feed throughs which connect to the motor windings. Remove 6 feed through bolts (for 2 motors) and the mounting bolts, then the inverter comes out.

These kind of cost reductions are essential to enable mass market electric cars.