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Old 19th May 2005, 07:47 PM   #1
taj is offline taj  Canada
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Default transformer weirdness

Hi, can one of you electronics whizes help me understand this...

I bought a 16VAC 40VA inline (like a laptop's) transformer and I can't figure out what's going on with the secondaries. Most of it seems normal to me. Here's my measurements on the 4 output wires:
White -> Red = 18v and .8 ohms DCR.
White -> blk = 9v and .4 ohms DCR
red -> blk = 9v and .4 ohms DCR

So far it looks like a normal 18 volt CT.

Green -> Red = 33v and infinte DCR
Green -> white = 18v and infinite DCR
Green -> red = 25v and infinite DCR

So how does this green (earth/ground wire) fit in? I don't understand where those voltages come from.

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Old 19th May 2005, 08:04 PM   #2
taj is offline taj  Canada
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Default also

I accidently deleted the sentence that said...

'the green wire shows 0-ohm DCR to the primary side earth/ground prong."

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Old 19th May 2005, 09:58 PM   #3
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Let me guess ... you measured those voltages with a digital meter with a 10M ohm input impedance, right?

What you are seeing is capacitive coupling between pri and sec putting common mode volts between sec and ground. All perfectly normal.
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Old 20th May 2005, 02:28 AM   #4
taj is offline taj  Canada
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Default Thanks!

Well there yah go.

Thanks again.
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