I used to make jokes about rectifying the line cord. Or even throwing a
wire up over the powerline and rectifying it for the power amp.
Using a transformer isolates your circuit from the mains. I was a computer
engineer at one time. We were having a severe problem with resets on one of
our systems out in California. It would just "Lock UP" and start alarming.
This particular deal was a building automation system. Automation goes away
at that point.
We hooked up all sorts of monitoring equipment on the mains to see what sort
of problems were coming in through the power company and I was appalled by
the crap that electrical equipment must tolerate.
On a 120V circuit we were seeing 300V millisecond pulses at least once an
hour and several cycles of 200-260 volt pulses every few minutes.
A transformer might smooth some of that out. Direct line to rectifier might
self destruct.
220-120 transformers are everywhere. They are called isolation
transformers. Plus you could have one wound by the likes of Pete Dahl or
any of the other suppliers to any size you desire.
I don't know what you are trying to do, but a SOLA CONSTANT VOLTAGE
transformer with the output rectified and filtered could give you quite a
SEMI-Regulated power supply. At least variations in input voltage would
provide you with a constant supply to the rectifiers.
You would want a lot of capacitance and a step start would most likely be
required.
BOB DD
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of kg7hf@comcast.net
Sent: Thursday, January 25, 2007 6:58 AM
To: amps@contesting.com
Subject: [Amps] power supply transformer
I am not sure I'm sending this correctly, but here goes.
I want to build a 120 volt DC source that can supply ~35 amps. I would like
to have the primary either 240 (typical) or 120 v AC. It doesn't have to be
regulated, but must be somewhat well filtered. My question is about
transformers, this type of transformer does not seem to be a common item.
Has anyone ever heard of a 240/120 primary 120 secondary at these high
current levels?
Why do I need to use a transformer in the first place, can I not simply
rectify and filter the two legs of the 240 without a transformer?
Thanks
Paul (KG7HF)
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