This is the 3rd comment on Lion tech and costs- and it is all about
inverters, ie VFDs.
A VFD or Variable Frequency Drive, today similar internally to a
brushless servo, is a critical component in a high-power motive application.
VFDs are common off the shelf tech., available from everywhere, and
really cheap from imports sources, often pretty good..
except that they ARE NOT !
A 100 kW - 200 kW VFD is well known tech, but they are only made in
small quantities, for industrial use, today.
A Siemens VFD of 200 kW might be 62 kg in mass.
Most of mass is for cooling.
Costs 10.000-20.000 $ retail.
Costs 5000 $ + to make, internally, to Siemens (Yaskawa, etc.).
Is about 92% efficient.
Contrast:
The Tesla inverter = VFD is about 30 kg in mass.
== 96% efficient.
Made from 13 (? iirc) parallel sets of cheap IGBTs, about 70 in total.
Costs about 300$ in components to make.
Components are TO-247 IGBTs, 2x14 pieces per leg for 84 IGBTS in total.
https://www.pntpower.com/on-tesla-electric-vehicles-semiconductor-packaging/
Pic
https://www.pntpower.com/wp-content/uploads/2015/09/Damaged-IGBTs-e1442318721253.jpg
Tesla has been making their own, and they had made about 13 versions, by
2016, always getting it cheaper, smaller, and more efficient.
The peak power has gone up from 1000 amps, to 1700 amps, at 400V.
The absolutely most important factor is efficiency (and cost).
4% more losses, ie 92% efficient vs 96%, at 400 kW, means 16 kW of heat
in lossses.
The 16 kW of extra heat will melt a metal box of 22 kg, in a few
minutes. As in red hot.
So the few extra % of efficiencies are critical.
And THAT is why the older, industrial, VFDs are big, heavy, and costly
to make.
Efficiency => less heat loss, => more reliability, => cheaper to make.
(More performance, arguably not important, since performance is already
more than good enough.)
This year 2017 tesla probably will make 100.000 cars, more or less, some
with 2 motors = 2 inverters.
No-one else on earth until 2020 or so, not all the Big Auto
manufacturers together, will need,
or have designed,
or make,
120.000+ identical inverters, ie mass scale,
cheaply and well ie with high efficiency.
There is no Q. that the chinese manufacturers and the auto parts makers
like Magna, Delphi etc. will at some point have something similar.
This will means inverter prices dropping from 10.000$ to 400$, while
efficiencies rise from 92% to 96%+.
This will probably take about 2 years, so calendar year 2018/2019.
Fwiw..
A fast google on digikey showed TO-247 OGBTs at 5-16€ each, qty 50-500.
So probably about 2€ each, qty 100k inverters, or 8.4M units total (84 x
100k).
Or about 160€ / inverter, add some pcbs, auxillary components, 20 kg alu
cooling etc.
--
-hanermo (cnc designs)
Posted by: Hannu Venermo <gcode.fi@gmail.com>
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