[ARC5] 24vdc power

[Charles]

It is also necessary to remember that the transformer rating does not 
give DC ampere output in a 1:1 ratio unless you have a choke input 
filter. From the Signal Transformer Catalog 892340 (available for 
download online), on page 38:

> The secondary currents shown in the tables are RMS ratings. Depending 
> upon rectifier circuit configurations, the RMS secondary current is 
> different from the DC output current. This is indicated in the chart 
> below:
>
> Full-Wave Center-Tap Choke Input = RMS Secondary Current is 0.7 x DC Amps
>
> Full-Wave Center-Tap Capacitor Input = 1 to 1.2 x DC Amps
>
> Full-Wave Bridge Choke Input = DC Amps
>
> Full-Wave Bridge Capacitor Input = 1.6 to 1.8 x DC Amps
>
> For example, in a F.W. Bridge circuit with a capacitive filter, if the 
> load is 1 Amp DC, the RMS Secondary current is 1.6 to 1.8 Amp RMS.
>

So I needed a 250 amp (5 KVA 20 volt) transformer to deliver 150 DC 
amps... and at that current level, the bridge rectifier repetitive 
forward rating is non-trivial, as is the heat generated. I used a big 
heat sink and a muffin fan.

-Charles,WB3JOK/0


On 9/5/22 19:31, arc5-request at mailman.qth.net wrote:
> From: Bob kb8tq<kb8tq at n1k.org>
> To: MICHAEL ST ANGELO<mstangelo at comcast.net>
> Cc: ARC-5<arc5 at mailman.qth.net>
> Subject: Re: [ARC5] 24vdc power
> Message-ID:<4F446E03-9F04-4E3F-A0FC-8BE25F92746B at n1k.org>
> Content-Type: text/plain; charset="utf-8"
>
> Hi
>
> One option is to stack some number of smaller transformers:
>
> This would be one candidate (based on a very quick search):
>
> https://www.antekinc.com/an-10425-1000va-25v-transformer/  <https://www.antekinc.com/an-10425-1000va-25v-transformer/>
>
> The same folks who made that come up with a wide variety of
> stuff up into the 1.5 KVA range. What they have today likely
> will not be what you find in a couple of months.
>
> If you bought four of the ones above, you would be up
> around 150A into your load. Voltage would be a tad high.
> A lower voltage / higher current version likely will pop
> up at some point. They have had them ( = 20V versions)
> in the past.