Post subject: Current vs. Voltage Transformer
postPosted: 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.
This explanation seems a little too
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
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
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 talking transformers.
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
"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."
When CT's 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 across it.
Basicly, if you disconnect
the secondary of a CT, be prepared to get the heck knocked out of