High quality 120V to 240V AC Mains transformer for permanent install

[Brian Roth]

A couple of other comments re. this situation.

1. A receptacle like the one I linked in post #7 is totally "legal" in the USA for 240V applications, but will require a variety of adapters/pigtails to interface with the many different types of AC mains connectors used worldwide. Read and weep (LOL):

https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets
2. I'm at a loss about how to handle a situation where a client shows up with multiple "foreign" (to the USA) pieces of equipment that all require 240 VAC at the same time. I guess you could have multiple NEMA 6-20R receptacles (as linked in post #7 above) installed and multiple "pigtails" and adapters available. It would appear that at least a few NEMA 6-20R receptacles receptacles in both the control room and the various tracking areas would be required to handle the various possibilities.

Bri

 

[ccaudle]

So lets say you have your 110v supply , neutral bonded to ground at the utillity in the usual way , then you have a 240 step up with a centre tapped ground , what happens if someone makes an audio connection between a 110v and a 230v powered device

Nothing happens because both devices have their chassis connected to protective earth conductor, which are all connected together at the service entrance. Draw out a diagram of the connections.

Theres inherent differences between the US 110v and the 230v EU system

Other than voltage they are very, very similar. EU requires ground fault interrupters on all circuits, US only requires on outdoor circuits, or outlets near water (kitchen and bath). You are allowed to put fault current interrupters on any circuit in the US, it is just not required.

He says a Euro 240V is Hot, Neutral and Ground. Whereas U.S. 240V outlets are 2 x 120V Hot with no neutral, and a ground

Modern equipment (anything built or modified since roughly 1960) cannot make any assumptions about one incoming wire being at the same potential as protective earth, both lines must be insulated and floating from chassis. So unless you have something which was built in the 1930's to 1950's and never updated to modern wiring standards hot/hot/ground is fine.

Is my intuition to have an isolation transformer overkill?

Yes. I knew someone who kept a small balanced power isolation transformer around and just used it when needed, typically with some guitar amplifiers. That is probably the best path, and maybe you never even need to acquire one.

I used to have a fairly large isolation transformer that I had wired as balanced power for my audio equipment, but it was physically large, over 100lbs (45kg) and I eventually decided that it did not provide any noticeable performance improvement, so I gave up using it the next time I had to move equipment around.

In my pea-brain, that is TWO phase power

It is single phase because the two hots come from a single transformer winding. 3-phase power requires 3 transformer windings, and the power to each leg is offset by 120 degrees. (Just TMI background information, I am sure you have heard or are familiar with the 3-phase wiring scheme.)

I'm at a loss about how to handle a situation where a client shows up with multiple "foreign" (to the USA) pieces of equipment

In server racks it is common to have a power distribution bar which has IEC sockets providing power, and IEC-to-IEC cords to connect to the IEC inlets on the server power supplies. I think the technical description would probably be an IEC 60320 C14 to C13 cable, or maybe more correctly C13 to E.
Wiki C13/C14 description

I am not sure if you could get one of those distrubution strips and E to BS 1363 cables for British gear, E to CEE 7/3 socket cables for German gear, E to CEI 23-50 for Italian gear, etc. but that seems like a possible solution.
Something like this with appropriate adapter cables:
Hammond IEC 5 outlet strip

 

[Brian Roth]

It is single phase because the two hots come from a single transformer winding. 3-phase power requires 3 transformer windings, and the power to each leg is offset by 120 degrees. (Just TMI background information, I am sure you have heard or are familiar with the 3-phase wiring scheme.)



In server racks it is common to have a power distribution bar which has IEC sockets providing power, and IEC-to-IEC cords to connect to the IEC inlets on the server power supplies. I think the technical description would probably be an IEC 60320 C14 to C13 cable, or maybe more correctly C13 to E.
Wiki C13/C14 description

I am not sure if you could get one of those distrubution strips and E to BS 1363 cables for British gear, E to CEE 7/3 socket cables for German gear, E to CEI 23-50 for Italian gear, etc. but that seems like a possible solution.
Something like this with appropriate adapter cables:
Hammond IEC 5 outlet strip

Indeed, after working professionally in this business for nearly 50 years, I am quite familiar with USA single phase and three phase power systems. I was attempting to KISS for the current discussion. I only brought it up to "cover my a$$" in case someone actually encountered three phase power in a commercial building or a McMansion. and discovered 208 VAC leg to leg (Wye) or the "wild" 240 VAC leg in a Delta system. I wasn't attempting to add confusion.

FWIW, there is actually an obscure 2 phase design:

https://en.wikipedia.org/wiki/Two-phase_electric_power
"Split phase" would be the correct description for common USA power distro:

https://en.wikipedia.org/wiki/Split-phase_electric_power
For many years, I have had a "problem" in my mind regarding the popular IEC connectors, since they are used internationally for both 120 VAC as well as 240 VAC connections. AFAIK, there isn't a method to determine which voltage will be provided via an IEC receptacle without poking a meter into the receptacle. This is in stark contrast to the NEMA connectors which are very different in design for the different voltages.

Again, I'm not trying to be a "jerk" about this, but attempting to provide some common sense comments about USA power systems and methods to accommodate 240 VAC equipment made abroad.. Hence, my meandering remarks.

Bri

 

[JohnRoberts]

I am a little apprehensive about giving advice about odd mains power wiring.

I see two concerns.
#1 human safety ... a 240VAC GFCI/RCD breaker should insure human safety even without a neutral or safety safety ground connection in the outlet.

#2 keeping the recording gear happy may be another issue and I defer to our EU manufacturers here. I see some plugs with an obvious extra contact (safety ground?).

To completely mimic the EU 240 hot leg, a 1:1 isolation transformer could tie one end of the secondary winding to neutral to appear correct on paper.

Good luck...

JR

 

[Matt Syson]

One comment to add here is that 'Europe' does not (quite) have unified connectors. In one way the really established standards are the thickness and spacings of the live and Neutral pins. Earth (ground safety connection) may be by a side strip contact or a third (round *) pin which does have the advantage of 'forcing the correct ''polarity' (defining which pin is live and which is Neutral)
Some seemingly similar connectors simply aren't, where (I think) some receptacles won't accept plugs from other European* countries however hard you try to force a plug that appears to fit but won't. Shuko have both a hole to accept a ground pin AND a strip on the side to make contact in some countries that use that method. All equipment assumes that either power pin COULD be live so switching and fusing regulations for the inside of gear reflects that. Double pole mains switch and sometimes 2 fuses I think.
*Brexit has neatly excluded the UK from quite a bit of this as the 13 Amp plug with integral fuse is now relegated to an island off the coast of Europe plus parts of Asia. There was a search for Brexit benefits and I can confirm that standing on a (13 Amp plug) is a lot more painful than standng on many of the 'legacy' EU plugs. I believe that a Residual (leakage) current breaker (30 milliamps) is a requirement for new builds and probably renovations across most of Europe. effectively forcing all power wiring (and lighting circuits) into defined live/neutral pairs assists in preventing radiation of 'hum' fields AND makes fault finding considerably easier since both live and it's Neutral are switched by the breaker (unlike the UK). My elderly French house has a handy connector box with 4 brass screws(bolts) with Neutral and 3 phases of 230 Volts for you to wrap the wires around. the bakelite box has a convenient 'thumbscrew' so you can get access with no tools. It escaped being bombed by the Allies in August 1944 so all is good!