# [EVDL] could new space amplifier design also be useful in electric cars?



## EVDL List (Jul 27, 2007)

Let me see if I have this right. You're suggesting building a controller 
with vacuum tubes. You know, those wonderful, warm, glowing, energy-wasting 
bottles inside the back of radio and television sets until the mid-1960s? 
That's what this device is.

Now, I'm not an engineer, but I seem to recall reading that tubes have 
soldiered on in high power, high frequency applications such as broadcasting 
and radar, because they can be cheaper and easier to build than 
semiconductor devices for those extremes of duty. And at very high power 
levels, the energy wasted by the heated cathode becomes a trivial portion of 
the energy used. (Someone please correct me if any of that's in error.)

But for DC? For low frequency (AF and below) AC? You certainly >could< do 
it, but would you want to? Would it offer any real benefit? 

My first inclination is to say "probably not," but I'm not really qualified 
to say. Instead I'll invite Lee Hart to weigh in. I think he's pretty 
close to my age (Back in the '60s, I used to build electronic hobby projects 
with tubes). He also has a refreshingly open "mad scientist" mind about 
such matters. ;-)

It's also worth pointing out that there is nothing "new" about this device, 
despite the fawning, dumbed-down, USA Today style of the physorg.com piece. 
(Wow! That's about 33 times as fast as your internet service!) The TWT was, 
as you can read in the WP article, invented almost 70 years ago; they've 
just made a bigger one and supposedly improved the efficiency. (One comment 
asks, "Is this an ad for L-3 Communications Electron Technologies' TWTs ?")

A little healthy skepticism can be useful when reading such sources.

David Roden - Akron, Ohio, USA
EVDL Administrator

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## EVDL List (Jul 27, 2007)

Short answer is NO, but they have their uses because they are extremely
sensitive and do not create internal noise to mask very weak radio and radar
signals and echos,

Our EV's operate with about 20,000 watts of continuous power. The
transmitter to produce that for a TV station carrier wave using a Klystron
tube or transistors is four feet in diameter and 12 feet long plus
approximately 2,000 cubic feet of support electronics, not including the
power company generator plant etc to provide operating electrical power.

The vacuum tube they speak of is only one millionth of an inch in diameter,
and thousands are used to pass one millionth of an amp.

These were originally announced in 1980 when I was an Engineering Aid in a
Large Scale Integrated Circuit Design Group helping eight Engineers and two
other Aids design and debug 9600 Baud modems for the "Telnet." the Internet
was about ten years away

The "Traveling Wave Amplifier Tube was a military Secret in 1967 when I
first worked with them. These certainly brought back some OLD memories!
Thanks, Dennis



> Geopilot <[email protected]> wrote:
> 
> > I just wondered if the new space amplifier design could also be useful
> > in electric cars?
> ...


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## EVDL List (Jul 27, 2007)

> Geopilot wrote:
> > I just wondered if the new space amplifier design could also be useful
> > in electric cars? It's lighter and more efficient than solid state.
> > Obviously it amplifies radio waves but could it be converted somehow to
> ...


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## EVDL List (Jul 27, 2007)

> David Roden wrote:
> > Let me see if I have this right. You're suggesting building a
> > controller with vacuum tubes... My first inclination is to say
> > "probably not"... Instead I'll invite Lee Hart to weigh in... He has
> ...


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## EVDL List (Jul 27, 2007)

> On 20 Aug 2009 at 22:42, Lee Hart wrote:
> 
> > The precharge circuit for a controller can be implemented with
> > exactly one part -- a vacuum tube. Power the filament from the grounded 12v
> ...


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## EVDL List (Jul 27, 2007)

Gentlemen, Perhaps my memory is stale in this topic as I went to solid
state after 1980, but for the fifteen years plus I worked with tubes I
seem to recall an internal voltage drop of 20 to 40 volts even at only
five or ten milliamperes. and a DC impedance at five kilo-ohms so how
long were you going to wait for that precharge? It could take a couple
minutes at 5,000 times the controller input capacitance, times five to
obtain 99% charge voltage and that would be 35 volts or so less than
"Pack" voltage... That 100 watt light bulb looks better to me, as a o=
ne
amp tungsten constant current device (sorta constant.). PS. My
electronics professor back in 1963 to 1965 was Doctor David Bellair, one
of the inventors and patent holder on the pentode vacuum tube. He really
enjoyed teaching vacuum tube theory, and I did well in his class.
(Please Excuse me if I go too far, but I haven't taken my hypertension
prescription yet today.) Dennis Miles, KF4EYO, Senior Certified
Electronics Technician. Director of E. V. Training Institute Inc in
Central Florida -)> 

----- Original Message -----
From: "David Roden"
To: "Electric Vehicle Discussion List"
Subject: Re: [EVDL] could new space amplifier design also be useful
in electric cars?
Date: Fri, 21 Aug 2009 01:36:22 -0400




> On 20 Aug 2009 at 22:42, Lee Hart wrote:
> 
> > The precharge circuit for a controller can be implemented with
> > exactly one part -- a vacuum tube. Power the filament from the
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> > > The precharge circuit for a controller can be implemented with
> > > exactly one part -- a vacuum tube. Power the filament from the
> > > grounded 12v circuit, and the cathode to heater become an isolated
> ...


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## EVDL List (Jul 27, 2007)

> Dennis Miles wrote:
> > I
> > seem to recall an internal voltage drop of 20 to 40 volts even at only
> > five or ten milliamperes, and a DC impedance at five kilo-ohms so how
> ...


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## EVDL List (Jul 27, 2007)

If you really want to save couple of $$ or so on precharge
resistor, I'd suggest to use heating element as such resistor.

MES water heaters actually sort of have this function - there
is special input to momentarily turn it on and discharge
controller's (or inverter's) capacitors for maintenance.

So the element can as well be used to pre-charge, and perhaps
even ceramic core based heaters still can be used for this purpose.

Can someone tell me what's the issue of just using parts meant
for the job? There are plenty of ICLs (Inrush Current Limiters) 
specifically mentioning precharging of DC link capacitors
as main application, for instance Digikey part 495-3451-ND
or similar. If this is the cost issue, they certainly cost
less than a tube, and for few thousand $$ conversion extra $3
won't make or break it anyway.

I realize using a vac tube may be is cool and exotic, but
why? Just for fun, bragging rights, be unique or to prove
it can be done while a proper resistor is sufficient?

Victor




> David Roden wrote:
> > On 20 Aug 2009 at 22:42, Lee Hart wrote:
> >
> >> The precharge circuit for a controller can be implemented with
> ...


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## EVDL List (Jul 27, 2007)

> Victor Tikhonov wrote:
> 
> > Can someone tell me what's the issue of just using parts
> > meant for the job? There are plenty of ICLs (Inrush Current
> ...


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## EVDL List (Jul 27, 2007)

Roger, I hear you. If some one just presents you a $8 choice
or $23 choice, of course the answer is straight forward,
but I suppose more is involved. As I often keep saying,
else we all would drive Toyota Corollas around.

This part was just example I found in 15 sec search;
granted, you'd need right ratings part and it can be
more than $4.50 for the tube you mentioned.

So then appears like this is only about the money (less than
$20 worth difference)...

I wonder how long a tube filament will last in a vibration prone
environment. I know in old days car radios were tube based,
but I also know tubes no longer are in use today (though they do
work!) for good reasons.

Dont get me wrong, I'm not saying don't use tubes. Probably
if you use graphite lead out of a 0.02 pencil as load resistor
it might also work and be cheaper, but it doesn't mean you should.

I suppose people don't use vac tubes for precharging not
because they don't know it is possible (most don't anymore
but it can be searched online and found), but probably because
spending even $20 more and do it in a straight forward and
reliable fashion is preferred vs. what is just doable.
I guess, I don't speak from a hobby point of view here.

Victor




> Roger Stockton wrote:
> > Victor Tikhonov wrote:
> >
> >> Can someone tell me what's the issue of just using parts
> ...


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## EVDL List (Jul 27, 2007)

> Victor Tikhonov wrote:
> > Can someone tell me what's the issue of just using parts meant for
> > the job? There are plenty of ICLs (Inrush Current Limiters)
> > specifically mentioning precharging of DC link capacitors as main
> ...


----------



## EVDL List (Jul 27, 2007)

----- Original Message -----
From: "Lee Hart"
To: "Electric Vehicle Discussion List"
Subject: Re: [EVDL] could new space amplifier design also be useful
in electric cars?
Date: Fri, 21 Aug 2009 18:44:23 -0500




> Victor Tikhonov wrote:
> > Can someone tell me what's the issue of just using parts meant for
> > the job? There are plenty of ICLs (Inrush Current Limiters)
> > specifically mentioning precharging of DC link capacitors as main
> ...


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## EVDL List (Jul 27, 2007)

Simple, nice. There are a lot of this style thing in TV's, Power
supplies etc.

But I wonder if an NTC would be better. Start at a high resistance and
then drop resistance as precharge progresses.
The reason I say this is suppose we chose that last part on the
datasheet. 100ohm initially

so if we have 300V, we start at 3A with a spark and when the caps are
1/2 charged the PTC is at 125 ohm and the charge current drops to 1.2.
obviously the PTC at less amps will cool down and current will increase
but the rate will slow as the voltage difference drops and the
resistance increases.

No if instead we had an NTC it could start at a high resistance very low
current and then ramp up to whaterver static resistance we put in the 
circuit. No spark on startup and then ramp to max precharge amps for a
faster precharge.

Just brainstorming, I think for precharge we need a static resistance, a
dynamic resistance and a diode.???


> If you really want to save couple of $$ or so on precharge
> resistor, I'd suggest to use heating element as such resistor.
>
> MES water heaters actually sort of have this function - there
> is special input to momentarily turn it on and discharge
> controller's (or inverter's) capacitors for maintenance.
>
> So the element can as well be used to pre-charge, and perhaps
> even ceramic core based heaters still can be used for this purpose.
>
> Can someone tell me what's the issue of just using parts meant
> for the job? There are plenty of ICLs (Inrush Current Limiters)
> specifically mentioning precharging of DC link capacitors
> as main application, for instance Digikey part 495-3451-ND
> or similar. If this is the cost issue, they certainly cost
> less than a tube, and for few thousand $$ conversion extra $3
> won't make or break it anyway.
>
> I realize using a vac tube may be is cool and exotic, but
> why? Just for fun, bragging rights, be unique or to prove
> it can be done while a proper resistor is sufficient?
>
> Victor
>

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## EVDL List (Jul 27, 2007)

Did I miss something? PTC is 3A and 12x4 is .050A
If we need 7 PTC we would need 402 tubes? 402 * ~8$ = $2994.90 and some
under hood heat
Oh, and don't forget to derate 75% for vibration, and wait until they
cool before you begin your drive.




> > Victor Tikhonov wrote:
> >
> >
> >> > Can someone tell me what's the issue of just using parts
> ...


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## EVDL List (Jul 27, 2007)

The right tube? 5AU4 ? http://www.drtube.com/datasheets/5au4-ge1960.pdf
2 diodes each 1A continuous 5A max and a 50V drop.

too bad a 5V filiment, maybe 2 6CA4's with filiments in series.

Nostalgia : http://www.drtube.com/tubedata.htm

It is surprising how low the power ratings are compared to semiconductors.

I wonder if a good solution would be to use a mosfet as a resistor,
driven by a pic micro that could start at zero accelerate to max
precharge and then shutdown. It would have an ign and start input and a
latched relay output. Humm, I wonder if this already is being done?


But it might make a nice little product, like the link10 companion board



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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> > I wonder if an NTC would be better. Start at a high resistance and
> > then drop resistance as precharge progresses.
> 
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> > Did I miss something? PTC is 3A and 12x4 is .050A
> 
> I was on vacation last week, and didn't have access to my tube manuals.
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> > The right tube? 5AU4? too bad a 5V filament
> 
> It's a directly heated filament -- the filament is also the cathode, so
> ...


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## EVDL List (Jul 27, 2007)

> > eff Shanab wrote:
> >> Did I miss something? PTC is 3A and 12x4 is .050A
> >
> > I was on vacation last week, and didn't have access to my tube
> ...


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## EVDL List (Jul 27, 2007)

> Jeff Shanab wrote:
> >> The 12X4 data sheet says...
> 
> > Wow, the only datasheet I found on the net was not that informative.
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart <[email protected]>wrote:
> 
> > "With the two plates in parallel, our precharge "resistor" is about
> > 200-260 ohms. Curtis suggests a 250 ohm precharge resistor for their
> ...


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## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> >> With the two plates in parallel, our precharge "resistor" is about
> >> 200-260 ohms. Curtis suggests a 250 ohm precharge resistor for their
> >> 1221 controller, which has 32 x 220uF capacitors = 7040uf = 0.00704
> ...


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## EVDL List (Jul 27, 2007)

> Victor Tikhonov wrote:
> 
> > So then appears like this is only about the money (less than
> > $20 worth difference)...
> ...


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