On 3/7/2013 10:17 PM, Jim Mueller wrote:
On Thu, 07 Mar 2013 09:50:11 -0500, rickman wrote:

On 3/6/2013 8:13 PM, Tim Williams wrote:
wrote in message

snip


I'm not familiar with the concept of voltage transformer vs. current
transformer. How do you mean that?

Current transformer measures current (its winding is in series),
potential transformer measures voltage (in parallel).

Series and parallel with what? I'm not following this.

snip

An electric circuit consists of a source of power, a load, and something
(like wires) connecting them. Transformers can be used if the source is
providing alternating current. A voltage transformer is connected in
parallel with the load so that the source, the transformer, and the load
all see the same voltage. It can also be used to match a load to a
source. A common example of a voltage transformer is the power
transformer in a piece of equipment that changes the AC line voltage to
whatever other voltages are required by the equipment.

A current transformer, on the other hand, is connected in series with the
load so that the source, load, and transformer all have the same current
flowing through them. The most common use of a current transformer is to
measure the current flowing into a load. A clamp-on ammeter is a common
example.

Historical examples of voltage and current transformers are the "picture
tube brighteners" that were commonly used in TV sets to prolong the
useful life of the CRT. There were two types, parallel and series. The
parallel types were used in transformer operated TVs and consisted of a
step-up transformer to raise the heater voltage of the CRT above normal
to increase emission. The series type was used in sets with the tube
heaters in series and consisted of a step-down transformer that raised
the heater current above normal. Of course, raising either the voltage
or the current also raised the other. These were, respectively, voltage
and current transformers.

A loop antenna is a distributed source with the voltage being generated
along the length of the wire and also having a magnetic field so that it
can be used as part of a transformer. This blurs the distinction between
a current and voltage transformer.

Is this a current transformer or a voltage transformer?
.--------. .--------.
| | | |
| C||C
VAC C||C Load
| C||C
| | | |
`--------' `--------'

--

Rick