Current transformers, I suppose...

[Tim Williams]

Pic from the guy I got them from.
http://webpages.charter.net/gradyrm/NEW 09-16-06/# 017.JPG

Electrically, they appear to be inductive, 45 ohms DCR, about 120 henry,
rather nonlinear suggesting laminated iron. I didn't note capacitance, but
it's sizable from a high frequency perspective (probably negligible at line
frequencies). Didn't drive to saturation. Assuming toroidial construction,
a winding looped through shows a turns ratio of about 4000:1, kind of odd
but certainly high.

Any random comments? (Genome, keep your hemmoroids to yourself.)

My question, ballpark how much current and frequency might these be good
for? Anyone familiar with similar devices?

Oh, and no I don't happen to have the part number with me. That's a good 50
feet away, to hell with looking!

Tim

 

[Paul E. Schoen]

Pic from the guy I got them from.
http://webpages.charter.net/gradyrm/NEW 09-16-06/# 017.JPG

Electrically, they appear to be inductive, 45 ohms DCR, about 120 henry,
rather nonlinear suggesting laminated iron. I didn't note capacitance,
but it's sizable from a high frequency perspective (probably negligible
at line frequencies). Didn't drive to saturation. Assuming toroidial
construction, a winding looped through shows a turns ratio of about
4000:1, kind of odd but certainly high.

Any random comments? (Genome, keep your hemmoroids to yourself.)

My question, ballpark how much current and frequency might these be good
for? Anyone familiar with similar devices?

Oh, and no I don't happen to have the part number with me. That's a good
50 feet away, to hell with looking!

Tim

These look like the sort of CTs that are in high current circuit breakers
with electronic trip devices. A three pole breaker would have three CTs,
and the mounting looks like one could be added in the middle, where there
is a hole for a third conductor. The round holes with square notches look
like they could accommodate rectangular as well as tubular bus. This could
be for a two pole breaker, which is normally the same frame as a 3 pole
with the center contact assembly removed.

Most CTs have 5 amp secondaries, but the high resistance and high ratio
makes me think these have 100 mA secondaries. In that case, they would have
a primary current rating of 400 amps, and probably would be able to handle
10 to 15 times that before saturation (so that instantaneous currents could
be properly measured). Since the CTs also supply power to the trip device,
it makes sense that they would provide 20-100 mA over the normal range of
operation. The trip devices usually have a backup battery or capacitor so
they still operate with no current flow, but normal currents would keep it
charged.

You can test these CTs by winding 10 turns of heavy wire (8 AWG or so)
through the hole, and then energizing the secondary with a variac. Read the
output current with a clamp-on, and see where the ratio becomes non-linear.
That is the "knee", which is about the maximum these will handle.

Good luck,

Paul
www.pstech-inc.com

 

[Robert Baer]

Pic from the guy I got them from.
http://webpages.charter.net/gradyrm/NEW 09-16-06/# 017.JPG

Electrically, they appear to be inductive, 45 ohms DCR, about 120 henry,
rather nonlinear suggesting laminated iron. I didn't note capacitance, but
it's sizable from a high frequency perspective (probably negligible at line
frequencies). Didn't drive to saturation. Assuming toroidial construction,
a winding looped through shows a turns ratio of about 4000:1, kind of odd
but certainly high.

Any random comments? (Genome, keep your hemmoroids to yourself.)

My question, ballpark how much current and frequency might these be good
for? Anyone familiar with similar devices?

Oh, and no I don't happen to have the part number with me. That's a good 50
feet away, to hell with looking!

Tim

Laminated iron seems to imply the laminations are standard silicon
steel, and so the nominal frequency would be 50-60Hz, and the highest
suggested frequency would be 400Hz.