three-phase power supply

[dutch diy]

A lot of effort, by all diy-ers, is put in getting a good, steady, DC- Rail voltage from a one-phase mains power supply.

If you spend that much amount of effort in reducing ripple why do we not switch to a three-phase mains supply.

iso getting one 300VA Toroid, you need three 100VA toriods, but the rectified voltage is far nearer to DC.

sure, you need a different wall-socket to plug in the amp. But 3-phase in-house is not that complicated.

I've not done it, but has somebody tried this??

[Da5id4Vz]

I dont think a lot of us can get 3 phase in our homes without extreme construction costs from the utilaties, if they will even consider it.

I dont think Ive seen 3 phase primaries within 3 blocks of my home.

This is an area were living in an aprtment building can be a real advantage.

I always did want to live in a converted warehouse.

-Dave

[JensRasmussen]

Hi,

I have worked with CROWN PA amps that run on 3 phase mains.

In denmark 3 phase mains are in most homes

When I was an apprentice somebody at work modified a "normal" power amp to run on 3 phases. The result was obvios - more power and more "kick"

I don't know if the same result - With kick - could be made by adding more caps to a singel phase amp

\Jens

[Circlotron]

I have 3x 240v 60A at home but simply have it split to power, lights and oven. I always imagined I would do something 3-phase-ish but it never happened...

With a normal 3 transformer setup you can wire the 3 primaries from neutral to each phase and the secondaries in a star configuration. With a full wave rectifier this will give you 300/360Hz ripple.

If you add a second set of 3 transformers with secondaries 1.732 times the voltage of the other three (and current ratting 1/1.732 times) and connect these 3 secondaries in delta config and run them to their own full wave rectfier you will also get 300/360Hz ripple.

So what? The magic thing is that there is 30 degrees phase difference between star-star and star-delta, so if we parallel our two full wave bridges via an interphase reactor (google for details) then we have a dc supply with 600/720 Hz ripple. Not much ripple either for that matter. Very little choke and cap needed.

[Da5id4Vz]

3 phase has always been great for motors.

I can see obvious similarities for amplifiers.

Your 3 phase Crown, was it one of the legendary MRI power supplies? (oops just read it was PA gear, there were legends here in the US about surplus magetic resonic imaging power suplies that were Crown Delt-O amps w/ 3 phase power suplies)

I'm envious of the 3 phase in the home.

[Vortex]

hm.

I asked two electricians about this all. Both of them have already built several tube amps in the 80's. They think it's absolutely senseless for normal amplifiers. It just simply doesn't matter.

Now, what?

[Christer]

For most people it is probably both cheaper and simpler to just
use larger capacitors than to use three-phase. There will still
be ripple also with the three-phase solution.

[azira]

Originally posted by Da5id4Vz
I dont think a lot of us can get 3 phase in our homes without extreme construction costs from the utilaties, if they will even consider it.

I dont think Ive seen 3 phase primaries within 3 blocks of my home.

This is an area were living in an aprtment building can be a real advantage.

I always did want to live in a converted warehouse.

-Dave

Assuming you're in the US... Most electric dryer hookups are run from 220 Volt supplies. This is actually a 3-phase system. Actually the electric company should be sending 3-phase electricity down the wire to your junction box. I thought it was the standard. Your typical 110 is just 2 legs of the 3-phase.

not that you want to run a powercord from your garage to your living room.....
--
Danny

[maylar]

Originally posted by Christer
For most people it is probably both cheaper and simpler to just
use larger capacitors than to use three-phase. There will still
be ripple also with the three-phase solution.

3 phase full wave rectified DC has only 5% ripple. If you use a regulated power supply, you may not even need input filter caps (assuming you regulate at a point below the valleys).

But for U.S. residential areas, 3 phase is not really available. It's an industrial thing.

[dutch diy]

3-phase is readily available here so that only introduces minor problems.

I'll play with the idea for a while and do some googling.

thanx for the suggestions