Siemens: New EV Motor+Inverter Combination Cuts Costs

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Siemens has developed a new approach to electric car design wherein the EV’s motor is housed together with the inverter — thusly reducing material use, weight, and, of course, cost.

Given that inverters are used to transform the DC electricity supplied by an EV’s battery to the AC electricity used by the motor, the “secret” to the new approach is simply to set it up so that both the motor and the inverter share the same coolant. Simple, right?


“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,” as the company explained in a recent release.

Given that costs can be lowered somewhat substantially this way, this certainly seems to be a worthwhile development.

“Aside from the obviously important benefit of cutting costs, the reduced weight is quite important since that helps to boost an electric car’s range, the only real weakness electric cars have compared to gasoline automobiles. Cutting weight and improving range was actually the main aim of the Siemens engineers who worked on this,” Sustainnovate writes.

“The more efficiently packed system also creates about 6-7 liters of additional cargo space, which could be used to put in a larger battery.”


Siemens provides some of the technicals of the new system:

The engineers adapted the housing (of the integrated Sivetec MSA 3300 drive unit) 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.

Clever. But you sort of wonder why nobody has taken this approach before. Isn’t it an obvious low-hanging fruit? Is there some issue here that we’re missing?

Image Credit: Siemens

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James Ayre

James Ayre's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy.

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