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Zapped 6th May 2003 07:14 PM

Zen V4 power supply
 
I am building a Zen v4 with two power transformers (Toroid 320 va, dual 18v secondaries in series) and 24,000 microfarads of C per side. My question is: when I place the primary sections in parallel, should I use two of the specified inrush limiters--one in series with each transformer? The specified device is only rated at 5 amp and I don't know what to expect in terms of total primary load for the two Transformers in parallel. Also, can I use a SPST switch and one AC line fuse (at what value? the article shows a 3 amp fuse but for the case of only one transformer and supply), or do I have to use two separate AC fuses at 3 amps and a DPDT switch (in other words, two completely separate power supply circuits sharing only the power socket and the grounding bridge diode arrangement?

BTW. How come there are no DC supply fuses in the circuit? Would this mess up the regulator?

Zapped 6th May 2003 07:15 PM

opps, I meant DPST switch.

JOE DIRT® 6th May 2003 07:45 PM

Hey zapped.....I would set it up this way....first a dpst switch then off the switch have a fuse to go to each transformer then your current limiter...this way your mains are separately protected

a fuse on the secondary output can be easily done and I prefer one there as it can protect any supply caps which are costly



Cheers!!The DIRT®

Zapped 12th May 2003 11:49 PM

Thanks Joe: I took your advice and bored another hole in the back panel for a second primary fuse. Assembling the power supply wiring now. Will have a limiter after each transformer.

Thanks again for the advice. Drilling another hole was no problem compared to the potential damage to an unprotected, or underprotected, transformer, I guess.

Larry Wright
Seattle area

nobody special 13th May 2003 12:53 PM

Quote:

Originally posted by JOE DIRT®
Hey zapped.....I would set it up this way....first a dpst switch then off the switch have a fuse to go to each transformer then your current limiter...this way your mains are separately protected

a fuse on the secondary output can be easily done and I prefer one there as it can protect any supply caps which are costly



Cheers!!The DIRT®

something to think about...
What would happen if the switch or wiring to it (before the fuses) shorts out?
Not likely, but it can happen. I would never place the line fuse after the power switch. It should always be the first connection after the power inlet.

Zapped 13th May 2003 04:03 PM

Yeah. That crossed my mind after thinking about how I would wire this thing up. I believe I indeed will string both primary fuse holders in parallel off the "hot" lead of the 3 terminal input, leading to separate poles of the power switch, thence to the separate transformers and their respective in-rush limiters. Having just been reminded last night that accidents do happen (water running into plugged laundry sink>>>flooded rug>>>>>mucho $ to fix), I resolve to avoid them wherever possible in the future.

Thanks for your valuable reminder.

Larry Wright
Seattle area

JOE DIRT® 13th May 2003 04:17 PM

quote: something to think about...
What would happen if the switch or wiring to it (before the fuses) shorts out?
Not likely, but it can happen. I would never place the line fuse after the power switch. It should always be the first connection after the power inlet.




you are correct all the equipment I design requires a fuse before anything for CSA approval

nobody special 13th May 2003 05:12 PM

Quote:

Originally posted by Zapped
Yeah. That crossed my mind after thinking about how I would wire this thing up. I believe I indeed will string both primary fuse holders in parallel off the "hot" lead of the 3 terminal input, leading to separate poles of the power switch, thence to the separate transformers and their respective in-rush limiters. Having just been reminded last night that accidents do happen (water running into plugged laundry sink>>>flooded rug>>>>>mucho $ to fix), I resolve to avoid them wherever possible in the future.

Thanks for your valuable reminder.

Larry Wright
Seattle area


That's exactly how I would do it... I like the idea of fusing each transformer seperately too.
Steve


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