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In Reply to: RE: Some fiddling and some discoveries... posted by bcowen on November 06, 2016 at 19:06:10
bcowen,I see you deleted your previous post. Here is my response.
You are correct for the maximum current rating of the secondary. The data sheet shows for parallel, 15Vac, the transformer is good for 1.66 amps.
25Va/15V = 1.667 amps.For the primary winding you have to divide 25Va by 115V.
25Va/115V = .217 amp.Recommended minimum fuse size rating.
.217 X 125% = .27ampMaximum fuse size rating.
.217 X 250% = .543 ampI would not use a fuse bigger than 1/2 amp on the primary side feeding the transformer. As for why the 1.25 slow blow fuse blew my bet the OP shorted out the secondary windings by hooking them up wrong, or, he wired them in parallel out of phase with one another. Hopefully he didn't fry the transformer.
A 1.25 amp fuse would be about 575% of the FLA of the primary.
.217 X 575% = 1.25 amp
Edits: 11/06/16 11/06/16 11/06/16Follow Ups:
You are right... I accidentally hooked them up parallel which blew the fuse.
Yes, I did delete that post. After Shovel's comment on the amp rating of the IEC filter, I went back and looked at the spec sheet. And looked at it wrong - I didn't pay attention to the fact that it was a general spec sheet for several different models. Shovel (and you) were right, I wasn't, and as nobody had responded at that point I deleted the post rather than add unnecessary confusion to the mix.
Thanks for the detail on the amp rating. I just learned something. I thought the fuse needed to cover the amp draw of the transformer secondaries, which is what I was basing calculations on for MY power supply. Looks like I need to go back and recalculate! Greatly appreciate the explanation.
bcowen,Thank you for posting the schematic diagram for the IEC/switch/fuse/filter unit.
http://www.audioasylum.com/audio/tweaks/messages/20/202695.htmlIt helped a lot, at least for me, to know what all the thing did.
I still wonder if the safety equipment grounding conductor travels/passes straight through the thing.
Also I would have never thought it had a double pole single throw power switch, DPST.
As for the fusing of both incoming lines. The schematic diagram shows a jumper through the fuse clip on the neutral Line. That indicated to me a fuse should not be needed on the 120V unit. A neutral should never be fused. It can be dangerous in certain circumstances. What I don't know for sure is what the OP has. He could just pull the fuse on the N, neutral, side and check for continuity across the fuse clips.
I believe the unit is designed to be used on 240V as well as 120V power systems. That would explain the DPST power switch and both hot AC power lines fused. The thing is the 240V mains would have to be both Hot ungrounded conductors. Maybe for a Europe 240V balanced power system...
Jim
Edits: 11/07/16
It is designed to go to 240V. Maybe the medical uses require 240? Dunno. Either way, it seems to be a great solution for plug, filter and power switch all in one.
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