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 Post subject: Stepup transformer and voltage regulation?
PostPosted: Wed Dec 12, 2012 12:02 pm 
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Location: Golden Valley
My electronics knowledge is very limited, however I'm hoping someone can enlighten me.

I'd like to build a low RPM (up to 180 or so) wind generator and most of the free motors I find have a very poor RPM/Volt output 35-45/1v. My thought was to use a transformer to step up the voltage to a minimum 15v and then regulate that down to a charging voltage of about 14.5v. I realize that this would probably incur some losses but I'm wondering if it could work?

I'm thinking I can either track down a proper transformer or maybe wind one myself. I have a 115v-to-12.5VCT 2A that I think could work. If I skip the center tap that would be an effective 1:4.6 stepup, right?

My other option is to use a set of gears to raise the RPM, and is probably easier, but I prefer learning something new.

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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Wed Dec 12, 2012 5:53 pm 
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Gyvven wrote:
My electronics knowledge is very limited, however I'm hoping someone can enlighten me.

I'd like to build a low RPM (up to 180 or so) wind generator and most of the free motors I find have a very poor RPM/Volt output 35-45/1v. My thought was to use a transformer to step up the voltage to a minimum 15v and then regulate that down to a charging voltage of about 14.5v. I realize that this would probably incur some losses but I'm wondering if it could work?

I'm thinking I can either track down a proper transformer or maybe wind one myself. I have a 115v-to-12.5VCT 2A that I think could work. If I skip the center tap that would be an effective 1:4.6 stepup, right?

My other option is to use a set of gears to raise the RPM, and is probably easier, but I prefer learning something new.
If I'm not mistaken, using the transformer you have, in reverse, would give you roughly a 115/12.5 voltage ratio, or a boost factor of 9.2. If the primary voltage were 1v, then, the stepped up output would be something less than 9.2v, accounting for some loss. Also of course you have to consider total AC power, which will be roughly the same for the input and output sides of the transformer, with some slight loss due to heat. Consider if the output amperage in this configuration will satisfy the need. If you need a 14.5v charging source, either the input voltage to the transformer primary needs to be increased or you'd need a different transformer with a higher winding ratio.

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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Thu Dec 13, 2012 9:27 am 
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Thanks Wammie,

The system should be entirely DC, so no AC current should be in the system.

I have a couple of questions and maybe you can clarify a few things for me;

If I run DC current through the ends of the secondary winding, bypassing the Center Tap, shouldn't that provide the same ratio as 115VAC to +12.5 and -12.5 (which is a 25V swing)?
If I use the Center Tap and one end I think I'd get the 9.2:1 ratio, but half the amps, at least in my head.
What would happen if I ground the center tap and split the positive and attach to both ends? Would I get my 2 amps back and a 9.2:1 ratio?
The difference would be I'd start generating 14.5V at 3.5mph instead of 17mph assuming a 45rpm/1V output and no voltage drop.
How is the transformer Amperage calculated, from the Primary or the Secondary? If mine is 2A @ 115V on the Primary that should equate to 230W, correct?

Using bicycle chain and gears is starting to look pretty good.

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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Thu Dec 13, 2012 10:17 am 
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Transformers do not work with DC.

If you want to step up the voltage of a DC source you need some sort of DC to DC converter
which essentially takes DC input, chops it up into AC, steps it up with a transformer, then rectifies it back to DC.


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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Thu Dec 13, 2012 2:50 pm 
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That's what I was missing. I was wondering why I'd never seen anyone using a transformer for DC to DC voltage stepups or stepdowns.

Thanks.

I guess I'll be cutting up that old bike after all.

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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Sun Dec 16, 2012 5:30 pm 
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Use a voltage multiplier.

Also, look at the differences between a dynamo and a generator.


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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Tue Dec 18, 2012 5:43 am 
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http://www.rmcybernetics.com/images/mai ... ltip22.jpg

This looks fun

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 Post subject: Re: Stepup transformer and voltage regulation?
PostPosted: Tue Dec 18, 2012 9:18 am 
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smittex wrote:
Use a voltage multiplier.

Also, look at the differences between a dynamo and a generator.


A dynamo is a generator, but a generator isn't necessarily a dynamo. In a certain context the terms are interchangeable, but a dynamo produces DC, where a generator can produce either DC or AC (in which case it's generally referred to as an alternator).

contortpiezo wrote:
http://www.rmcybernetics.com/images/main/pyhsics/voltmultip22.jpg

This looks fun


It does, but unfortunately it's meant for AC to DC (from what I've seen so far), it's similar to a rectifier except the added caps push a little higher voltage to the next caps, and so on. I'm not sure if DC would work since I think it needs the AC oscillation to push the voltage to the next stage. I'm envisioning a ram pump, but I could be entirely wrong.

I did find a a couple of voltage multiplier circuits that were DC to DC but they could only handle 600mA. I'll keep researching, maybe I can find a circuit for higher amperage use. One way or another my knowledge of electronics will improve.


Thanks for all the ideas. If you're not constantly learning or trying something new then you're not living right.

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