[Amps] Re Direct rectification of AC mains to derive the amp, VDD, supply

[Carl]

So how do you filter out the harmonics?

Carl
KM1H

----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <amps at contesting.com>
Sent: Friday, September 20, 2013 2:41 AM
Subject: Re: [Amps] Re Direct rectification of AC mains to derive the amp, 
VDD, supply


> On 9/19/2013 1:52 PM, Bill Turner wrote:
>> Just one question: What is the voltage relationship between neutral and 
>> each
>> side of the 240 V lines?
>
> In North America, single-phase 240V is fed by a center-tapped transformer, 
> where you get 240V end to end, and 120 V from either end to the neutral, 
> which is connected to the center tap. In a breaker panel that has 240V 
> single phase, half of the 120V breakers are fed from one end of the 
> transformer, and half from the other. Load that need 240V get only the two 
> phase lines (the two ends of the transformer).
>
> As Peter Voelpel notes, much of EU, especially those countries whose 
> infrastructure was heavily destroyed in WWII, have settled on 3-phase to 
> many (most?) customers. That's harder in counties that have not suffered 
> that destruction -- there's so much legacy system there, and it's nearly 
> all single phase.
>
> What DOES happen a lot in the US, both in mixed residential and light 
> industrial districts of cities and even out here in the Santa Cruz 
> Mountains, is a bastard system called "high leg Delta," where the basic 
> distribution is 240V Delta, but with one side of the Delta having a 
> center-tapped secondary. The center tapped side feeds the 240V 
> single-phase customers, all three phases feed those larger users who need 
> it. The MAJOR downside of high-leg is that all of the harmonic current 
> goes to ground via the neutral fed to single-phase customers, so we suffer 
> from a TON of buzz (triplen harmonics of 60 Hz -- 180 Hz, 360, 540, 720, 
> etc.  I've measured an amp or more of this harmonic current in both here 
> in the mountains and in Chicago.
>
> There's a discussion of this in the tutorial I referenced.
>
> 73, Jim K9YC
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