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Operating UK equipment on US power

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David Allred:
From an electronics forum:

"To talk of "European" equipment here is not useful, since Europe has many different electrical standards, varying from country to country.

However, if the equipment concerned operates on a compatible voltage, and if the equipment concerned is not sensitive to the different AC frequency, then you could connect a European device to an American supply.

To take one example, the main difference between an American domestic 240 V supply and a UK 240 V domestic supply is the grounding/earthing arrangement. In the US outlet both legs of the 240 V supply are hot and are 120 V from ground. In the UK 240 V supply one leg is live and one leg is neutral (close to earth potential). In other European countries the supply voltage and grounding arrangements may be different.

As mentioned by other posters, European devices are designed to operate safely in a variety of different supply situations with both supply legs fully isolated and insulated from exposed parts. So a European nominal 230 V device can be plugged into a US 240 V socket without problems."

Can anyone confirm or refute this? Pic attached.
Thanks.

PS - I also saw that tying the outputs of a 2 pole breaker gives 240v (using neutral).  But does that not make every 120v breaker output 240v also by tying the 120v buses together through that breaker?

John Roberts {JR}:
You should be ok with modern gear... I would be nervous about plugging an old EU guitar amp into US 240VAC outlet as any stinger cap could be energized in both switch positions.

JR

David Allred:

--- Quote from: John Roberts {JR} on March 22, 2024, 10:43:13 AM ---You should be ok with modern gear... I would be nervous about plugging an old EU guitar amp into US 240VAC outlet as any stinger cap could be energized in both switch positions.

JR

--- End quote ---
The gear is a koi pond air pump.  :)

Mac Kerr:

--- Quote from: David Allred on March 22, 2024, 10:07:36 AM ---
PS - I also saw that tying the outputs of a 2 pole breaker gives 240v (using neutral).  But does that not make every 120v breaker output 240v also by tying the 120v buses together through that breaker?

--- End quote ---

This part sounds scary. You do not tie 2 120v legs together to get 240v. This is done with 240v breaker that keeps the legs separate. The 2 legs, which are each 120v but of opposite polarity are isolated from each other till they reach the load.

Mac

Erik Jerde:

--- Quote from: Mac Kerr on March 22, 2024, 01:40:56 PM ---This part sounds scary. You do not tie 2 120v legs together to get 240v. This is done with 240v breaker that keeps the legs separate. The 2 legs, which are each 120v but of opposite polarity are isolated from each other till they reach the load.

Mac

--- End quote ---

Yeah, tying the two legs of a US 120V 1PH directly together will make sparks and trip the breaker.

For this issue it’s probably important to have a little understanding of how power works.  In order for power to flow you need a difference in voltage.  For a standard 120V outlet you have a 120V hot leg and a (nominally) 0 volt neutral.  That gives a voltage potential of 120V when connected across a load.  For 240V UK power it’s the same except the hot leg is 240v.

Now in the US 1PH (single phase) power you usually get two 120V legs that are 180 degrees out of phase from each other.  Remember that AC power is a sine wave.  Without drawing a picture what this means in practice is that when one hot is 120V the other is effectively -120v.  When you connect a load across these two legs you get a voltage potential of 240v.  Think of it as one side is pushing 120V when the other is pulling 120v.  The load doesn’t care how the voltage differential is achieved it just operates when it’s present.

Going back to the idea of tying the two phases directly together you can hopefully see how that creates a short circuit which trips the breaker and how even if it didn’t if you attached those to one side of a load and neutral to the other you wouldn’t get a voltage potential across the load of 240V.

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