Date: Mon, 02 Aug 2010 10:07:29 -0400
From: hanslg@aol.com
Subject: Re: [TowerTalk] Fwd: shack wiring
Hi Jim,
Yes, you are right, a three phase system aggravates the problem but it is also
present on on split phase feed.
Worst case probably never happen, but my house in Brooklyn receives its power
from a gigantic, three phase transformer, buried in the street. This
transformer is feeding several houses on the block.
An easy method to see if you have a three phase feed is to measure the voltage
across the hot legs. 240 volts probably a split 120/240 transformer,
208 volts and you most possible have a 208/120 volts three phase feed.
## I would know if I had 208/120 vac single phase ! That's exactly what I
had in my old condo yrs ago. 1st floor gets A-B 2nd floor gets B-C 3rd
floor gets A-C.. 4th floor gets A-B
Now, if you have identical power supplies, the harmonic are also identical. You
may have have different power supplies with different phase relationship
between the harmonics.
## the problems these days are when you have literally hundreds of pc's..all
running on 120 vac... in a gov't office, etc. They all put put globs of
harmonics.. which ends back out in street... and ends up as 'dirty power'
Bottom line is, if you large power supplies, us 240 volts feeder and supplies.
I believe most large supplies can be configured for 240 volts.
## Agreed. I was just using the example of hundreds of pc's as a worse case
senario.... which according to most power co's...is happening all the time.
My 253 lb dahl xfmr has taps for 198-208-230-240-250. My 120 lb pole pig [run
backwards] is 240 only. My small 46 lb dahl has dual 110 v winding's. All
of the above + 4 x more... hang off a 100A sub panel.. and also the 200A main
panel.
## high C HV B+ ham supplies are full of harmonics too... like really bad
PF.
Jim VE7RF
Hans - N2JFS
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