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Discussion Starter · #1 ·
I have an installation that needs a 240 volt line to neutral connection, the service is 480 volts 3 phase Wye feeding a 240 volt 3 phase transformer. This makes the 240 volts line to line, I need it line to neutral. I am thinking about putting a 277 volt to 240 volt step down transformer, the load will be less than 2 amps, will that cause any problems?

I have not been out in the field as an electrician for over 25 years and have forgotten what little I learned about 3 phase electrical installations, I now work as an electronics engineer at a small manufacturing company. I need the 240 volts to test/burn in power supplies for international destinations.

Don
 

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Hi Don, welcome to the forum. :thumbup:

I cna't speak for your power supplies specifically, but I have used and installed many Kinoton Film projectors that are designed for 240v line to neutral on a standard 240 volt line to line circuit with no problems whatsoever. (Kinoton officially ok's such a connection.)

Unless you power supplies have some filtering or surge suppression components that connect neutral to ground (or chassis) that are rated less than the 240v they might see, there should (I'd say comfortably will) be no problem connecting them 240 line-to-line for testing at least.

If you use a 277 to 240 step down transformer, you will have too low of voltage on the secondary due to the primary being fed only 240 volts..if you are giving the correct voltages coming from your intended branch circuit in your OP. Or, use a 480v to 240v step down transformer and ground/connect one leg of the 240v secondary to the primary side neutral to give you a neutral for your testing.

But I feel that if the voltage you have coming from your branch circuit is 240 line to line you are wasting money with an additional transformer.
 

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Discussion Starter · #3 ·
sorry I wasn't clear about the 277, it comes from the service, and powers all the lighting, so I think that the transformer will provide the 240 volts line to neutral. I have used the 240 volts line to line and yes it works just fine, but it does not simulate the conditions in other countries,and most of them use 240-220 line to neutral . I am currently using a step up transformer, 120 volts to 240 volts, and some universal power strips. I'm installing wall outlets with different sockets for the most commonly used plugs, and want the correct voltage for them
 

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Does the load really need 240 volts line to neutral? Most don't care about the ground reference as long as the plate voltage is right.

Is this an IEC or European made machine?
 

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How about using a buck/boost on your 277 and buck it 32 volts? KVA size of the buck/boost would be calculated on 32 volts so it wouldn't have to be very large.
 

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sorry I wasn't clear about the 277, it comes from the service, and powers all the lighting, so I think that the transformer will provide the 240 volts line to neutral. I have used the 240 volts line to line and yes it works just fine, but it does not simulate the conditions in other countries,and most of them use 240-220 line to neutral . I am currently using a step up transformer, 120 volts to 240 volts, and some universal power strips. I'm installing wall outlets with different sockets for the most commonly used plugs, and want the correct voltage for them
That's the way, I was going to suggest doing it. If you feel that you need a reference to the neutral, Just designate one leg of the 240 volt winding as a neutral and tie it to ground.
 

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If you only need 2 amps or less. Do you have access to an old 400 watt high bay fixture? If you can get a multi-tap or multiple voltage fixture, take the transformer out of it. Isolate and tape off the high voltage output. Find the 240 tap for your output then connect your 277 to the 277 input. The neutral is your common and 0 volt to ground. Double check with your voltmeter before final connecting a load. Those fixtures are being replaced by more efficient fluorescent fixtures and can be had for a song.
 

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Also keep in mind that in Europe not every install is 230 p-n., most are but exceptions exist. In Norway 230 volt IT (ungrounded) power is the norm with resi, older western Euro installations have 127/220 or 138/240 power where sockets just take both phases for 230 volts. Many (still modern) Euro none grounding plugs can also be reversed (non polarized) with either leg getting 230 volts to ground.

If you are testing these for true international use make sure you do a swapped polarity test, along with a hot-g-hot line test.
 
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