Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

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Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

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Hi folks. In summary a solid state transformer is less efficient, less reliable and more expensive than ye-ol passive 60 hertz transformer that are reliable as a rock.  Not sure why GM would tout them for feeding fast chargers. They're in prototype stage now but can't compete on basic parameters.  Passive 60 hertz transformers are 97% efficient. No-way 2 conversions in an AC to DC then DC to AC inverters are going to come close.  They use a 10-20khz smaller isolation transformer internal to the step up or step down side conversion. Replacing one large component (60 Hertz transformer) with thousands of electronic components is less reliable. I've always had it beat into my pointy engineering head to minimize component count. Which is also why id never own a Tesla with 6800 or so cells in their battery.
Have a renewable energy weekend
Mark in Roanoke VA

Sent from my iPhone

Begin forwarded message:

> From: "Hanson, Mark (GE Renewable Energy)" <[hidden email]>
> Date: September 7, 2018 at 1:07:28 PM EDT
> To: "[hidden email]" <[hidden email]>
> Subject: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication
>
> https://ieeexplore.ieee.org/document/5618255/
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Re: Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

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On 7 Sep 2018 at 13:16, Mark Hanson via EV wrote:

> Replacing one large component (60 Hertz transformer) with thousands of
> electronic components is less reliable.

I'm sure that's true.  But there's a lot of expensive copper in those boat
anchor 50/60Hz transformers.  And thanks to dumping-level Chinese component
prices, the electronic route is usually way cheaper.

Parenthetically, paradoxically, and similarly: from what I've read, the
digital electronic controls on the fancier household gadgets, such as
microwave ovens and electric space heaters, are actually cheaper to
manufacture than the less-featured old fashioned mechanical timers and
thermostats.

I suspect -- but don't know, not being an engineer -- that if they were
designed more robustly and built with higher quality components, the
reliability of the high-component-count solid state designs could be brought
much closer to that of the boat anchor transformers.  But then they'd
probably cost as much or more.

And maybe the constants in the equation will change when the upcoming US
tarriffs on Chinese components and subassemblies (but apparently not on
finished Chinese products, go figure!) kick in.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

Electric Vehicle Discussion List mailing list
In reply to this post by Electric Vehicle Discussion List mailing list
What about the diodes and filter capacitors to make reasonable DC affecting
efficency?  Linear parts are big and have a lot of loss.  Switching supplies
make up for it, are smaller, cooler, have a better power factor and can
self-protect during a fault.
David

-----Original Message-----
From: EV <[hidden email]> On Behalf Of Mark Hanson via EV
Sent: Friday, September 07, 2018 1:16 PM
To: [hidden email]
Cc: Mark Hanson <[hidden email]>
Subject: [EVDL] Fwd: A comparative efficiency study of silicon-based solid
state transformers - IEEE Conference Publication

Hi folks. In summary a solid state transformer is less efficient, less
reliable and more expensive than ye-ol passive 60 hertz transformer that are
reliable as a rock.  Not sure why GM would tout them for feeding fast
chargers. They're in prototype stage now but can't compete on basic
parameters.  Passive 60 hertz transformers are 97% efficient. No-way 2
conversions in an AC to DC then DC to AC inverters are going to come close.
They use a 10-20khz smaller isolation transformer internal to the step up or
step down side conversion. Replacing one large component (60 Hertz
transformer) with thousands of electronic components is less reliable. I've
always had it beat into my pointy engineering head to minimize component
count. Which is also why id never own a Tesla with 6800 or so cells in their
battery.
Have a renewable energy weekend
Mark in Roanoke VA

Sent from my iPhone

Begin forwarded message:

> From: "Hanson, Mark (GE Renewable Energy)" <[hidden email]>
> Date: September 7, 2018 at 1:07:28 PM EDT
> To: "[hidden email]" <[hidden email]>
> Subject: A comparative efficiency study of silicon-based solid state
transformers - IEEE Conference Publication
>
> https://ieeexplore.ieee.org/document/5618255/
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Re: Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

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In reply to this post by Electric Vehicle Discussion List mailing list
> In summary a solid state transformer is less efficient

I'm certain this is not true, even on a Pin vs Pout basis, and certainly not on a size or weight basis.

Eddy-current losses and I2R losses are greater the lower the frequency. By choosing the frequency and the ferroresonant components carefully, one can easily get 10x the efficiency.

To verify, find an old, heavy "wall wart" 60Hz transformer. Plug it in for an hour or so. Feel it. It's warm! Even with no load.

Now do the same with a switcher, even one with a higher power rating. It will remain cool to the touch. Even fully loaded.

But size and weight and (lack of) materials are where switching power supplies really shine. These are important concerns in a vehicle.

Jan

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Re: Fwd: A comparative efficiency study of silicon-based solid state transformers - IEEE Conference Publication

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In reply to this post by Electric Vehicle Discussion List mailing list
From: Jan Steinman via EV <[hidden email]>
>> In summary a solid state transformer is less efficient

> I'm certain this is not true, even on a Pin vs Pout basis, and certainly
> not on a size or weight basis.
>
> Eddy-current losses and I2R losses are greater the lower the frequency.
> By choosing the frequency and the ferroresonant components carefully,
> one can easily get 10x the efficiency.
>
> To verify, find an old, heavy "wall wart" 60Hz transformer. Plug it in
> for an hour or so. Feel it. It's warm! Even with no load.

Eddy current losses go UP with frequency. I2R losses don't correlate well to frequency. Higher frequencies reduce the wire length; but "skin effect" reduces the effectiveness of the wire (the higher the frequency, the shallower the current will penetrate into the surface of a conductor).

Transformer performance is mainly determined by the design tradeoffs. What did the designer care about? Size, weight, cost, efficiency? You can optimize for any of these at any frequency.

The efficiency of a dirt-cheap near-junk quality transformer is truly bad. Many of these have so little iron and such thin wire that the resistance of the winding is what limits the current; not the inductance.

Compare this to a quality 60Hz transformer. These routinely have efficiencies in excess of 95%, and can be as high as 99% if optimized for efficiency.

The main drawback of 60Hz transformers is not efficiency; it's size and weight.


--
Excellence does not require perfection. -- Henry James
--
Lee A. Hart http://www.sunrise-ev.com
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