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

[Jim Brown]

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