[GreenKeys] 120vdc at 4-5 amps?

[Bob kb8tq]

Hi

If you have a really big filter capacitor (and don’t mind the peak currents) you can 
do “ok” with an 84 V transformer. With a real world cap and parts, it will slump a bit
under load. Since motors are the intended target …. why put a big filter cap on it? 
Just rectify it and sent the result to the motors. 

Bob

> On May 2, 2018, at 3:13 AM, Alf Fisher <alffisher2 at gmail.com> wrote:
> 
> Hi Guys,
> I reckon you need around 85 volts into the rectifier to get around 120 DC out.
> A couple of 20-0-20 transformers with secondary windings in series wouldn’t be far off if you get the phasing right.
>  
> Alf
> G3WSD
>  
>  
> From: hwhall at compuserve.com <mailto:hwhall at compuserve.com>
> Sent: Wednesday, May 02, 2018 2:19 AM
> To: ksweek at mindspring.com <mailto:ksweek at mindspring.com> ; GreenKeys at mailman.qth.net <mailto:GreenKeys at mailman.qth.net>
> Subject: Re: [GreenKeys] 120vdc at 4-5 amps?
>  
> Couple ideas:
> 1.  Start out with the isolation transformer idea, find out what the final DC output is when rectified & filtered, cut into the transformer & take off some turns.  
> 2.  Make the above power supply but feed it with a variac instead of cutting up the isolation transformer.
>  
> Wayne
> WB4OGM
>  
> -----Original Message-----
> From: ken Schwieker <ksweek at mindspring.com>
> To: GreenKeys <GreenKeys at mailman.qth.net>
> Sent: Tue, May 1, 2018 6:25 pm
> Subject: Re: [GreenKeys] 120vdc at 4-5 amps?
> 
> If you use an isolation transformer you will end up with considerably more than 120 volts dc after rectifying and filtering. One possible solution is to get a variac, remove all the center hardware
> and wind enough turns of insulated wire for the secondary to produce the needed voltage.
> Ken S 
> 
> At 11:13 AM 5/1/2018, you wrote:
>> No, I don't need to run 100 loops at once. I have several pieces of gear with 120vdc motors and it would be nice not to have to plug/unplug them one at a time on my 1A supply.
>> Any suggestions about where to find a suitable transformer? -Â  Diodes and caps are no problem. I'll keep an eye out at the Dayton hamfest.
>> 
>> Nick England K4NYW
>> www.navy-radio.com <http://www.navy-radio.com/>
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