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RE- MICROWAVE POWER TRANSFORMERS
From: Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
Sent: Wednesday, October 22, 1997 12:17 PM
To: tesla-at-pupman-dot-com
Subject: RE- MICROWAVE POWER TRANSFORMERS
TL>From: "Alan G. Pope" <agpope-at-phonetech-dot-com>
TL>Subject: MICROWAVE POWER TRANSFORMERS
[ ... ]
TL>I stripped down an old J. C. Penny, large size home unit, and found a big
TL>brute that is rated at a 13 amp draw off the 115 V power line, and has a
TL>secondary of maybe 20-22 gage wire. The secondary output is well in excess
TL>of 1 KV (it pegged my meter at 1KV). I'll have to make a high-voltage probe
TL>so I can measure it.
TL>Anyway, the things have got some muscle, and should be useful for a number
TL>of different projects.
If any want a =real= microwave transformer (the kind =real=
men use), investigate the used-restaurant-equipment market.
Or better - the used-industrial-equipment market.
Some of those will really cook your goose (and the rest of you
also as well, if you're not careful!).
- - - - - - - - -
Note: Determining the output of a high-voltage transformer
does not require a high-voltage probe or meter of any
kind whatsoever -- and -- for safety sake none such
ought to be used. Ever. (Which is fairly infrequently).
1) - Get thee to a Radio Shack store (or its ilk, kin, or kith)
2) - Buy a 6-volt (or thereabouts) transformer.
Else - buy a =center-tapped= 12-volt
transformer and use 1/2 the secondary
to get your 6-volts.
3) - Connect the primary of the 6-volt transformer to the
120-volt line.
4) - Connect the 6-volt secondary to the =primary= of the
high-voltage transformer.
5) - The output of the high-voltage transformer will now be
at 5% of what it would have been if driven by its normal
120-volt input instead of the 6-volt test voltage.
Follow?
6/120 x 100 = 5% (Trust me)
For a 1000-volt transformer, the output will now
be a safe, sane, 50-volts. Which any bright 10-year
old (or foggy-thinking adult) could be trusted to
measure.
For real high-voltage transformers (say 25,000 volts) simply
compound the felony --
Proceed:
6) - Get a =second= 6-volt transformer.
7) - Power the second from the 6-volt output of the first.
That is, connect the first transformer to the 120-v
line as per usual. Use its 6-v. output to drive
the primary of the second 6-v transformer.
8) - The second transformer will now be delivering 0.3-v
output.
9) - Connect this source of 0.3-v. to the 120-v primary of
the 25,000-v high voltage transformer.
The 0.3-v amounts to 0.25% of 120-v. Ergo, the
output of the 25,000-v. transformer will be
62.5-v.
Which any (ever so slightly more advanced) 10-year
old can measure.
0.3/120 x 100 = 0.25%
or
5% x 5% = 0.25%
- - - - - - -
Like and similar results may be obtained by using a series
string of incandescent light bulbs and tapping across
one (or more) of the bulbs, i.e. using the string as a
resistive voltage divider. --For those who live in those parts
of the world (2 or 3, I believe) where there are no Radio
Shacks.
A variable autotransformer (e.g. "Variac") can likewise
be employed but this is somewhat hazardous unless run
thru a step-down transformer.
- - - - - - - -
While I'm pontdefecating --
A meter used to measure the output of a transformer should
=always= be connected =before= the power is applied (unless
your aim is to cook your meter (and your goose)). That goes
twice-over (and double) in the case of high-voltage measurements
(this is for those of you who still want to run out and spend
$200 for a high-voltage probe so you can test oven
transformers).
[ ... ]
Mentally operating at full
voltage, in -- Detroit, USA
Robert Michaels
FINAL EXAM:
Joe Blo (from South Kokomo) sells his kilovolt meter at a
rummage sale for $15 and buys two 6-volt transformers at
Radio Shack.
Each of the two transformers has an un-tapped 120-v.
primary and an un-tapped 6-v. secondary.
A) -- How many different voltages may be
obtained from these two transformers using
only the 120-v. house current as power
source and no other devices or equipment?
B) -- Extra credit:
What are those voltages?
Answers:
Will be distributed after all exam papers have been turned
in. Those failing will be excluded from the High-Voltage
Laboratory until shocked into their senses.
(Hint there are =more= than 8 different voltages obtainable)