OT: Power Supplies

[Gene Heskett]

On Saturday 20 November 2004 18:20, Bill Gradwohl wrote:
>RoboticGolem wrote:
>>Well that settles that.  I ran all day yesterday with no
>> problems... The memtest ran from 9pm - 1pm with no errors, but at
>> about 7:30pm last night when the washer and dryer were going that
>> it started up again.  Also there is a garage band that plays now
>> and again, and I am located (I believe) on the same grid as a
>> football stadium.
>>
>>Now the real trick, which one do I get.
>
>If you have serious power issues, and it sounds like you do, the
> best UPS is a Ferroresonant version. That's a technology, not a
> brand. A ferroresonant UPS uses the laws of physics to get rid of
> transients by using a very heavy transformer to smooth out any
> noise. I would also suggest you get a true on line UPS with
> sinewave output.
>
>These aren't cheap, but they're bullet proof.

Still OT, That depends on how you measure the size of the bullet.

Many years ago I was the engineer at an educational tv transitter 
site, uhf of course, so we measured our monthly power consumption in 
gigawatt hours.

One of the measures taken at station build time was a 250KW 3 phase 
Sola regulation/isolation transformer between us and the power grid, 
I'd estimate the core and windings went to around the 6000lb mark on 
the scales.  Huge affair on a concrete pad outside the building.

We fought with hum bars in the picture related to the 3 phase solid 
state hi voltage rectifiers non-zero reverse recovery time, which 
locked the phase of the voltage going up to the phase of the voltage 
going down for about 30 microseconds 6 times per cycle, and caused 
short light bulb life all over the building because of the nearly 2KV 
spikes that came out of the wall plugs caused by this same effect.

Several years later lightning finally blew that Sola to kingdom come.  
I mean 6000 lbs of well done Texas Toast. We were a day or so getting 
enough 500mcm cable rounded up to bypass it and get back on the air.  
4 pieces per phase & around 30 feet each long was a bit more copper 
than was readily available locally.

When we came back up, we were rather surprised that we were no longer 
troubled by 95% of this picture interference as it could now back out 
into the power grid and be absorbed much better.

That lightning bolt, the "bullet" if you will, must have been a real 
hoodoozy, but in the long run it did us a favor.  That place had a 
1069 foot tower, and I've seen lightning play around on the brackets 
holding the top beacon and lightning rods, getting that area so hot 
it outshone the 1320 watts worth of beacon to the point you couldn't 
see the beacons flashing for a few seconds as I drove toward it, and 
walk in the door 3 minutes later with absolutely no damages to repair 
99% of the time.

Towers like that are, generally speaking, pretty well grounded, the 48 
cubic yard base pyramid had a sheet of 12 gauge copper about 8" wide 
from the pivot ball socket down to its base many feet down, on all 4 
sides, installed before it was backfilled after the pour.  I'd expect 
the ground impedance was greater in microhenries than it was in 
milliohms.

-- 
Cheers, Gene
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Copyright 2004 by Maurice Eugene Heskett, all rights reserved.