3 phase power supply for audio !

I have 3 phase power at my house, on a 20 A breaker.
Yes, that's a ridiculous amount of power for an audio system.
But it does mean I don't have to have any 'bulk' capacitors because I don't have to store power to cover the zero volt crossover of a one phase system.
That would save quite a bit of money and improve reliability, one minor inconvenience is the connector.
A conventional amp can use an ordinary IEC socket to have a removable power cord but there appears to be no equivalent in 3 phase.
The standard 3 phase connectors are the size of beer bottles, and not even stubbies.
Anyone know a smaller connector that meets standards?
Or am I stuck with a non removable cable?

David
 
A 3 phase driven rectifier arrangement will still have ripple, just not as much. The only way to get rid of ripple, without capacitive storage, would be to have the number of phases go to infinity.

Which is of course ridiculous. Perhaps look into "power factor corrected" power supply designs, which suck current from the AC mains for pretty much the whole cycle, instead of just at the peaks of the voltage waveform.

I think going to 3-phase will give you only a marginal advantage. As in reduce the filter capacitor some, but not eliminate it.
 
  • Like
Reactions: 1 user
You need three transformers though if you are using the typical capacitor input supply.
Do really have something that wants alot of power?
I admit I might do this if I had access to 3 phases though.

Edit - Look at Boulder amplifiers. The obnoxiously large power connector is just part of the deal. Something to brag about.
 
What about Perilex plug?

Not available in Australia, and obsolete I understand.
I hoped for a modern connector like Neutrik Powerconn but can't find it.

...Perhaps look into "power factor corrected"...

Yes, that's one option, with boost converter on each phase the bulk capacitors could be eliminated,
Still need to filter a bit, of course.

What AC volt...?

It's the usual Australian, 230 V nominal phase to neutral, actually still 240 V.
(we "harmonised" with European 230 V but it just means we run at 230V + 5%, which is within spec.!)
So 415 V phase to phase, no wimpy 120 V here;)
And yes, reduction of turn on transients is one of the other benefits that inclines me to this approach.

Best wishes
David
 
Last edited:
You need three transformers...the typical capacitor input supply.
Do really...want a lot of power?

Three transformers is the other option. I haven't decided which way to do it yet.
I don't need the ~15 kW, no, but I do plan a fairly powerful system and I save on capacitors, if I make a simple switch-mode supply then save on transformers too.
Switch mode also eliminates any chance of DC offset problems.
I have a 3.6 kW inverter that I can use for parts, I'm kind of tempted.

A lab power system that I checked had 80VAC...

When I was in the USA I was surprised and a bit disturbed by how poor the typical house electrical system was.
Wouldn't meet minimum here (with allowance for different electrical codes of course)

Best wishes
David
 
Last edited:
Disabled Account
Joined 2002
My home has 3 x 80A 3 phase power which is extreme IMO and there are outlets at some spots with 16A CEE form connectors. I am quite fond of 3 phase power professionally (not many things in electro are so misunderstood as PE and 3 phase power) and I am an audio DIYer so suddenly I had a 3 phase transformer :)

Then I thought.... this is going too far. Built a 2 x 4W amplifier on single phase power instead.
 

Attachments

  • 25.32_1.jpg
    25.32_1.jpg
    17.2 KB · Views: 695
Last edited:
Disabled Account
Joined 2002
In general normal houses have 3 phase power here but only one is connected and this in sequence so L1, L2, L3, L1 etc. all with a 16A breaker. So the load of the street/neighborhood is divided over 3 phases. It depends on the EU country but in general 3 phase is more expensive than single phase. Therefor the Netherlands have a 2 phase system for induction cooking (to avoid higher costs). The 3 x 80A I have in Germany are outrageous certainly because the load is a fraction of that. The heaviest load is a 3 phase induction stove that is 12 kW with all fields active.

I worked with American colleagues but never got a positive impression of the power system there (from what they told me). Here UPSes are a precaution against risks but they rarely are needed as outages are rare.
 
Last edited:
My home has 3 x 80A 3 phase power...

Mine too! But it means I can run surplus industrial machinery that is inexpensive because there are fewer bidders with 3 phase.

...Built a 2 x 4W amplifier...instead.

Not a home theatre by the sound of it;)

Yes, our entire power system is a wreck. Free enterprise, you know. Especially in Texas, read about that.

It was while I stayed in Texas that I noticed this, and I still have friends there.
So I was motivated to read the stories of the failures in the snow storms some months back...oh boy.

...normal houses have 3 phase power here but only one is connected and this in sequence so L1, L2, L3, L1 etc. all with a 16A breaker. So the load of the street...is divided over 3 phases...

Similar here but my house happened to have all 3 phases to the meter board and a 3 phase 20 A breaker circuit available. Wonderful.

As for connectors, look at...

Thanks for the recommendation, actually the Han-A 4 pole + earth looks just what I wanted.

with the added transformers, i don't think there is a financial...

Instead of, say, a 2400 W one phase transformer I can use three separate 800 W transformers.
There is some economy of scale with just one unit but the three smaller transformers won't add up to that much more, if at all, because 800 W is a more common size and there is an economy of scale from the numbers made.
But I am inclined to use the switch mode solution, solves DC offset and saves on transformers.

Best wishes
David
 
Last edited:
For 3-phase you would normally use a 3-phase transformer, much less iron for the same power rating I believe.

And of course after the transformer you have all 6 phases available so can avoid caps altogether if you want: just rectifiers and a regulator. Or stick to the rect + cap design too with a smaller cap.
 
As some posters have already replied, with 3 phase you virtually do not need any smoothing capacitance, but to avoid having the transformer's own equivalent resistance limiting current surges, I still suggest using an electrolytic capacitor of about 1000uF. If the transformer has two secondaries per phase, you can use a delta connection for one set and a star connection for the other set. This doubles the number of phases in the system and you get 6. This is done in HVDC technology.

Please, be aware many people, including myself, do not have 3 phase mains electrical power. You have to check with books or some knowledgeable person whether the advice you are being given is practical.
 
Disabled Account
Joined 2002
I do not understand mentioning the use of small value capacitors. When going 3 phase the goal should still be as least voltage ripple as possible isn't it? Certainly with classic rectifier diodes and filter caps and audio being the purpose in which many go into great lengths doing silly things for marginal gains :) Must be a cultural thing to always try to make it as cheap as possible but that makes absolutely no sense when investing in 3 phase stuff as the caps will be the least expensive items.

Ruler flat DC is ideal, then choose caps going close in that direction. The gains of 3 phase voltages never crossing 0 add up and one should take in account 1 phase to go missing (I think I would use a phase monitoring relay). When choosing switchers what is the point of going 3 phase?

Anyway check the reliable CEE Form sockets and plugs for 3 phase power. These exist in 16A, 32A etc. and the 3 phase versions are red. All connectors for 3 phase power are quite sturdy because as you may know a 3 phase short means a lot of short circuit current. Even the tiniest 16A standard connection can deliver quite some power. What the general layman often does not see is that the power that can be delivered by a 3 phase system is destructive. Let's suppose using a tiny nice looking audiophile approved 5A 4 pin plug and a short circuit occurs right behind that puny connector. Stuff will literally explode. All the other stuff in the circuit will be designed for the possible currents/power. It will certainly not be according local safety regulations and possibly insurance companies will not pay for the damage then.
 
Last edited:
For 3-phase you would normally use a 3-phase transformer, much less iron for the same power...

It is theoretically possible to reduce the iron in a 3 phase transformer but that usually means stamped laminations like an EI transformer.
It seems the benefits of the toroidal core more than make up for the flux cancellation of the 3 phase style, at least at the lower power typical of audio.
Power stations and the like obviously have a different trade-off.

...If the transformer has two secondaries per phase, you can use a delta connection for one set and a star connection for the other set. This doubles the number of phases in the system...

Yes, that pushes the ripple down even further, it's a clever idea that I have seen but need to study more.

...to always try to make it as cheap as possible but that makes absolutely no sense...as the caps will be the least expensive items.

Well, it's not for a 2 X 4 W system;)
Decent quality power caps are expensive, for a powerful multi channel system it adds up.

...switchers what is the point of...3 phase?

1 phase switchers need so called "bulk" capacitors to cover the zero cross of the mains. It's just that they on the mains side.
A 3 phase switcher would need no bulk capacitors at all.
With a bit of power factor correction then there would be essentially no ripple at all.

Anyway check the reliable CEE Form sockets...

The Australian standard connectors are similar to the CEE and are excellent.
Well protected from dust and liquids, robust, sealed cable entry and strain relief.
Perfect in my workshop with lots of distance between pins for flash-over protection.
But they are massive, not practical for a removable cable like an IEC connector.
The Han connectors are rated to handle the power I require and may be my choice.
In any case I am very pleased to have learned about such a nice connector system.

Or you could build a power wall like they do in the trade shows,.

That's more or less the opposite of what I want.
Banks of capacitors in racks of amps does look impressive but is actually a clumsy, brute force fix.
I try for a smart, efficient, less expensive solution

Best wishes
David
 
Last edited: