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Old 6th June 2009, 04:14 PM   #1
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Default Wiring Power Transformer in Parallel

Hey all,

Go easy on me, this is my 2nd build I'm trying to wire Triad N-67A power transformer in parallel for 115 input voltage.

schematic

I understand "JUMPER BLK to BLK/RED" (connect black to black/red) and "BLK/YEL to BLK/GRN" (connect black/yellow to black/green), but what does the first part of the description imply, "BLK to BLK/YEL"?

Also, never worked with a shielded secondary...guessing the secondary "shield" gets connected to the power supply star-ground scheme?

Thanks again.

-Charlie
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Old 6th June 2009, 04:43 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
the two dots are the phasing of the windings.
They tell you where to connect Live.

For 220/240Vac operation connect the middle dot to the middle unmarked.
For 110/120Vac operation connect both dots to Live and both unmarked to Neutral.

Test that the phasing has been correctly marked and interpreted by powering up with a light bulb tester.
The bulb must stay "off" to indicate that the primaries are correctly wired.

I'm not sure, but I would connect the shield to Safety Earth which is the mains earth lead that is connected directly to chassis.
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Old 7th June 2009, 02:38 AM   #3
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"BLK to BLK/YEL"?

Connect one of your 115 volt inputs (hot or neutral) to the BLK and BLK/RED pair and the other 115 volt connection goes to the BLK/YEL and BLK/GRN pair.

I usually connect the shield directly to the GND terminal on the IEC (power input) connector. This should also be connected to circuit ground somewhere inside the device, either at the star point, or the ground terminal on one of the input connectors. Use whichever gives the lowest hum.
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Old 7th June 2009, 02:45 PM   #4
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by tubelab.com
I usually connect the shield directly to the GND terminal on the IEC (power input) connector. This should also be connected to circuit ground somewhere inside the device, either at the star point, or the ground terminal on one of the input connectors. Use whichever gives the lowest hum.
I don't think the shield is there to reduce hum.
Is it there to attenuate the capacitively coupled HF that tries to enter from the mains?
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Old 7th June 2009, 07:52 PM   #5
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Quote:
Originally posted by AndrewT
Is it there to attenuate the capacitively coupled HF that tries to enter from the mains?
Yes, that's what that xfmr was designed to do: reduce to a minimum capacitive coupling between the primary and secondary. It's not so much about keeping RF out, but rather power line spikes, which have predominantly high frequency components.
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Old 7th June 2009, 08:24 PM   #6
pointy is offline pointy  United Kingdom
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i think for 110v you would have the black+black red together for say live side

and the black yellow+black green together for neg

also the mid winding would go to ground via the chassis
you connect the white wire to chassis about one and a half inches or so from the transformer and towards the wall socket
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