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PostPosted: 17 Aug 2009, 07:02 
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Joined: 13 Jul 2009, 20:01
Posts: 92
Location: Space Coast Florida
Greetings!

Can someone tell me how power transformers are rated?

Edcor rates the transformer as, for example, 400 VAC. However, is that peak-to-peak or RMS or what?

I need to do some calculations, but not knowing the units is a show stopper.

Thanks!

Loren


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PostPosted: 17 Aug 2009, 10:18 
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Location: Space Coast Florida
Never mind. Manufacture said it was RMS. ;-)


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PostPosted: 18 Aug 2009, 10:22 
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Joined: 19 Jul 2009, 18:29
Posts: 14
I've got a transformer rated at 700V CT 120mA DC.

Because of the way the box is marked it appears to me that it is 700V rms CT at 120mA DC.

So once it is recitified, I'll have to take the actual voltage divided by the 700 times 120 to get the true load capacity of the transformer in mA.

I've split the secondary windings so I have two 350Vrms windings. I tested the isolation between windings with a HYPOT tester at work to 1500V to insure it is still properly insulated and safe to use the windings in parallel. I'll add a resistor in series with each winding to match them in case the turns ratios are not exactly equal.

Now I can get 350 * 1.414 = 500V dc

So the transformer capacity should be 700/500*120ma or 170ma DC.


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PostPosted: 18 Aug 2009, 20:56 
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Joined: 19 Jul 2009, 18:29
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Further question about power transformers:

Does anyone use voltage multipliers with lower voltage rated transformers ?

The reason I ask is I have two 60vct transformers that look like about 300VA capacity. I am considering using voltage multipliers instead of finding new transformers.

60V ct = 85V p-p.

2X = 170V at about 1.7A
3X = 255V at about 1.18A
4X = 540V at about 0.55A
5X = 425V at about 0.70A
6X = 510V at about 0.59A
7X = 595V at about 0.50A
8X = 680V at about 0.44A
9X = 765V at about 0.39A

Of course the cost is the additional capacitors and diodes with the associated losses.

However it seems to give a lot of flexibility.

Since I have two of these chunks of Iron, diodes and capacitors, I'm considering doing such with it.

Anyone see any missed hitches?


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PostPosted: 20 Aug 2009, 16:38 
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Joined: 08 May 2009, 08:20
Posts: 918
Location: Duesseldorf, Germany
Hi Gimp,

there are no problems using the mutipliers. You only have to keep in mind, that each doubler divides the output current. Double voltage = half the current. And with using more and more multiplier stages you'll get a lot of current loss. That's all.

_________________
Cheers,
Tom.

Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


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