Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
Current vs. Voltage Transformer - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: Current vs. Voltage Transformer
Thu Dec 23, 2004 11:06 am
I've been looking around the internet
and have so far been unsuccessful in finding info on the differences
between current and power transformers (3-phase).
My guess is that
a current transformer steps-up current by having less secondary windings...
and a power transformer steps-up voltage by increasing the number of
secondary windings when compared to the primary windings.
explanation seems a little too simple!
Another thing i was wondering
about, is that a superior of mine was telling me that when dealing with
current transformers, it's important not to short circuit the terminals
(or open circuit them, i can't remember which one)... when i asked why
this was the case, he said he wasn't sure, but that it caused arcing
between the terminals.
Would there be a similar issue to consider
in power transformers?
Does this make any sense!? I would really
appreciate a response.
Thanks for your help
Unread postPosted: Mon Jan 24,
2005 2:31 am
A voltage transformer is used to either step up
or step down a voltage.
That is usually what people refer to when
A current transformer, or "CT" as it is
sometimes called, is usually used when measuring large currents. A good
example of this is a clamp on ammeter. When measuring a 150 amp current
there is no way that 150 amps is flowing in the meter. The meter steps
the current down proportionally to the current you are measuring in
the wire the meter is clamped around. CT's are designed to operate with
the secondary shorted.
The book I have(Delmar's Standard Textbook
of Electricity) says that...
"The secondary winding of a CT should
never be opened when there is power applied to the primary. This will
cause the transformer to produce a step-up voltage that could be high
enough to kill anyone who comes in contact with it."
are used 1 loop of wire goes through the core of the CT. Remember, the
CT secondary is designed to be used short circuited. The secondary of
the CT has several windings.....when disconnected, the CT turns into
a step up transformer. If the voltage you are measuring is 480 and the
CT secondary has 50, 100, or even 200 turns.....you now have a 1:50,
1:100, or 1:200 step up transformer. That is going to hurt if you get
Basicly, if you disconnect the secondary of a CT,
be prepared to get the heck knocked out of you. :wink: