Date: Sat, 14 Sep 2013 19:14:53 +0000
From: Manfred Mornhinweg
To: amps@contesting.com
Subject: Re: [Amps] Rectifier equilization?
Bill,
> > FYI for next time, 6A10 diodes have become preferred by
> > many for high power use because of their 6 amp continuous
> > and 400 amp surge ratings and moderate cost.
> I don't mean to say anything against 6A10 diodes, they sure
> work fine. But they are HUGE overkill. Even if the filter
> capacitors had zero equivalent series resistance, and the
> power outlet where the amp is connected had zero impedance,
> and there were absolutely no inrush limiting system used,
> and the power were switched on in just the worst possible
> moment (peak of waveform), just the resistance of the HV
> transformer will limit the current to roughly 20 to 30A,
> or maybe 40A if the transformer is really beefy. And such
> a condition of course doesn't happen in real life -
> specially the line from which the amplifier is powered does
> have some resistance and also some inductance. In practical
> use, in a normal home, it would be really rare to see more
> than 15A inrush current.
>
> 1N5408 diode has a 200A surge rating, which is still big
> overkill. The humble 1N4007 with its 30A surge rating would
> be about the right part to choose for a cost-conscious
> builder! It's also comfortable with the average current.
> Rated at 1 ampere average, a bridge rectifier using strings
> of 1N4007 diodes is good for 2 amperes. That gives enough
> headroom for a legal limit amp.
>
> Feel free, of course, to use big diodes, if it gives you
> peace of mind. But it shouldn't be technically necessary.
>
> Manfred
As usual, excellent reasoning Manfred. However...
I bought fifty 6A10 rectifiers for $17 including shipping
(34 cents/each). 1N5408s might've been even cheaper but
these were still dirt cheap and, this way, if/when I NEED
the extra capacity, I'll have it.
For a one-off homebrew power supply, the few pennies extra
cost is nothing. Of course, it would matter if I was in a high-
volume low-margin manufacturing scenario. I'm not. :)
vy 73,
Bryan WA7PRC
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