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RE- EXAM/Microwave Transformers
From: Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
Sent: Monday, November 10, 1997 11:43 AM
To: tesla-at-pupman-dot-com
Subject: RE- EXAM/Microwave Transformers
Dear People:
Last week in replying to a post about testing microwave oven
transformers I made the point that no kilovolt meter was needed
or ought to be used.
The post appeared more than once - an error on my
part in manipulating my mail reader. Please forgive.
Rather than of a kilovolt meter, I made the point that a 6-volt
transformer (or a pair of them) should be used to energize
the primary of the transformer under test.
- - - - - -
At the end of the post I posed an "examination question":
Given two such transformers, and only two,
plus the 120-v ac line, how many different
voltages may be obtained?
I hinted that there were at least 8.
- - - - - -
Now, in response to overwhelming demand (well, two of you
actually), here is the answer:
Twenty-one different voltages (yes, 21!) may be obtained -
neglecting trivial repetition.
I. ONE TRANSFORMER BY ITSELF:
=============================
1) 120-v line by itself = 120-v
120-V. INTO TRANSFORMER PRIMARY
-------------------------------
2) 120-v in = 6-v out
COMBINING THE 6-V IN SERIES-AIDING & SERIES-OPPOSING
WITH THE 120-V:
3) 120-v + 6-v = 126-v. (aiding)
4) 120-v - 6-v = 114-v. (opposing)
120-V. INTO =SECONDARY=
------------------------
5) 120-v in = 2400-v out
AND AGAIN, COMBINING THIS SERIES-AIDING AND SERIES-OPPOSING:
6) 120-v + 2400-v = 2520-v
7) 120-v - 2400-v = 2280-v
Note - A Radio Shack transformer will not very long
withstand these high voltage -- But -- many so-called
filament transformers from the vacuum-tube era =will=!
Even those not specifically rated for use with high-
voltage tubes will thus serve well in intermittent
"Experimenter Duty".
At this point, we have 7 different voltages counting the
120-v line itself and using only one of the transformers.
6 of these voltages may now be applied to either the
primary or the secondary of the second transformer (the
first - the 120-v - is Trivial)
II. TWO TRANSFORMERS IN CASCADE (Output of First as Input to Second):
====================================================================
ABOVE 6 VOLTAGES INTO =PRIMARY= OF SECOND TRANSFORMER:
--------------------------------------------------------
8) 6-v in = 0.3-v out (convenient for testing 10-100-kv
transformers)
9) 126-v in = 6.3-v out
10) 114-v in = 5.7-v out
x) 2520-v in = 126-v out (Trivial result - not counted)
x) 2280-v in = 114-v out (Trivial)
x) 2400-v in = 120-v out (Trivial)
COMBINING THE ABOVE 3 (NON-TRIVIAL) VOLTAGES WITH THE 120-V
LINE IN SERIES-AIDING AND SERIES-OPPOSING:
11) & 12): 0.3-v + (and -) 120-v = 120.3 & 119.7-v
13) & 14): 6.3-v ditto = 126.3 & 113.7-v
15) & 16): 5.7-v ditto = 125.7 & 114.3-v
COMBINING THE 3 VOLTAGES 8), 9), 10) WITH THE PRIMARY VOLTAGE
WHICH PRODUCED THEM - SERIES-AIDING AND SERIES-OPPOSING:
x) & x): 0.3-v + (and -) 6-v = 6.3 & 5.7-v (Trivial)
17) & x): 6.3-v ditto 126-v = 132.3 & 119.7-v
(The latter is Trivial)
x) & 18): 5.7-v ditto 114-v = 119.7 & 108.3-v
(The former is Trivial)
NOW - THE FIRST 7 VOLTAGES CAN ALSO BE APPLIED INTO THE
=SECONDARY= OF THE SECOND TRANSFORMER:
-------------------------------------------------------
x) 6-v in = 120-v out (Trivial)
x) 126-v in = 2520-v out (Trivial)
x) 114-v in = 2280-v out (Trivial)
19) 2520-v in = 50,400-v out (Ka-Boom! - Unless you are using
an x-ray filament transformer
or perhaps some types of poten-
transformers)
20) 2280-v in = 45,600-v out (softer Ka-Boom)
21) 2400-v in = 48,000-v out (softest Ka-Boom)
Wheeew!!, in --
Detroit, USA
Robert Michaels
P.S.:
Exam Question - Joe Blo (from South Kokomo) had such a good
time with the above that he went out and bought a =third=
6-v transformer from Radio Shack:
- Using only the 120-v line and the 3 transformers
how many different voltages may be obtained?
- Extra Credit: What is a good place around here
to go and have one's head examined?