Re: gEDA-user: [OFF] high current amplifier

[Gene Heskett <gene.heskett@xxxxxxxxxxx>]

On Wednesday 20 May 2009, Joerg wrote:
>DJ Delorie wrote:
>> Levente Kovacs <leventelist@xxxxxxxxx> writes:
>>> 230V times 100A is something I dont want to even calculate.
>>
>> It's 23000 :-)
>>
>> My air conditioner draws 123 amps at 240 volts for the first few
>> seconds.  That's almost 30kW.
>
>Seconds and not fractions or a second? Yikes! Unless it's a 10-15 ton
>unit that doesn't sound normal. Did you find some of the power hogs with
>your new board by now?

Off topic reply, but could be germain too.

Not even a 40 horse compressor in a 22 ton (rated, yeah sure) Lennox will draw 
that much for that long.  Its startup was a peak in the 250 amps/phase area, 
and the reason I say area is that a std 400 amp scale on an amp-probe on any 
phase line swung up to 250 and back down to its running of about 39 amps/phase 
in a purely ballistic fashion as the startup surge was only 6 or 7 cycles of 
the 208/3 phase line.

Now it really gets off-topic.

That was one of those _must_ _work_ units else a tv station was off the air 10 
(or less) minutes after it failed.  It was also probably responsible for some 
of the early ozone holes over the antarctic as it was severely under fanned on 
the condensor side, and I had to add 20 pounds of freon in the fall to keep it 
working right until it wasn't needed, and bleed that 20 pounds back off as 
spring turned into summer.  This went on for 8 years on my watch, back in the 
70's, and long before they started regulating all that stuff.

2 ea. 1100rpm 1/2 horse motors turning 24" fans just didn't cut it.  I got 
tired of that one spring and fixed _some_ of it by taking a failed motor to 
town, having the brackets stretched to carry 2 horse 1800 rpm motors, 
replacing the motor with a 2 horse 1800 and repeating it the next week with 
the second one.  2 horse wasn't quite enough as they ran a couple of amps over 
nameplate when the condensor was relatively clean.  When those blades failed 
(fatigue cracks, caught before they made shrapnel), I replaced them with 
blades with an inch less pitch.  That allowed it to continue to work until the 
ambient went over 80 degrees without bleeding freon to keep the high side 
under 400 psi and the compressor currents under 43 amps/phase else the 
overcurrents in the compressor would trip.  Based on those results, I would 
have said that a single 20hp motor, running at full load pulling a quad 
torrington wheel with each half about 16" wide & 14" diameter, would have been 
about right.  That could have been throttled with a 4' square louver driven by 
a M-H proportional control Modutrol to regulate the high side pressures/temps 
and made it work all year.  Some of the crappy designs foisted off on the 
industry by supposedly reputable, old line makers are amazingly loaded with 
excrement.  I even called Lennox and they swore on a stack of bibles that 
those 2, 1/2 horse motors were enough.  I asked what was the expected 
operating temperature range and he said 75-90F outside.  I said "and what 
happens when you have enough heat load to need it, but the outside temp is 
33F?"  "Its not designed to run at those temps."  Why did you sell it to the 
State of Nebraska then, you did have the specs, I've seen them?  Mumble.

Obviously I wasn't talking to a real engineer so I asked him where he got his 
sheepskin.  More mumbling.

Being a tv engineer for the state NETV commission, when the nearest help is 
200 miles away in Star City, (Lincoln NE) means you truly are a Jack Of All 
Trades. :)  Those 8 years were _very_ educational, but I left because I was 
still not the lead dog, so the scenery never changed. :)

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The NRA is offering FREE Associate memberships to anyone who wants them.
<https://www.nrahq.org/nrabonus/accept-membership.asp>

Stray Alpha Particles from memory packaging caused Hard Memory Error on 
Server.



_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user