Pri Voltages - Switching power supplies

[QWTLNW]

Does the primary of a modern day switching power supply care if the voltage is line to line or line to neutral ?

See attachment. Line clearly marked "L-N-G". And in the data sheets it only refers to Line-Neutral voltages.

I figured that the 100-240V rating simply made it "worldwide compatible" w/ typical worldwide PH-N voltages.

But now I have been told by several people that modern switching power supplies don't care if the voltage is line to neutral or line to line. If using line to line just connect the 2nd hot leg to the lug marked for the neutral.

Can't find any decent internal wiring diagrams for these units to review.

Any input or help is deeply appreciated. (designing service and distribution for a sign that has 258 of these little demons)

 

[GoldDigger]

Overseas 220V or similar will be single ended, with one side grounded and the other at line voltage.
The potential problems that I see are:
1. The neutral terminal and wiring, all the way into the rectifier DC source may not be rated for a significant voltage to ground. Not likely, but needs to be considered.
2. Any internal fusing will only be in the line wire, not the neutral wire. In the case of am internal fault to ground (see also item 1) that could cause big problems. One fuse on the line terminal only will protect against overloads though.
3. It would almost certainly conflict with the installation/operation instructions for the power supply.

 

[mopowr steve]

Well if anything goes wrong at least they were honest..... See it was made by Mean Well:lol:

 

[Jraef]

It will not "care", it just reads the voltage between L and N and auto adjusts to whatever it sees. People here get worried because they keep associating Neutral and Ground as if they are one and the same. They are not, in fact there are applications where N is NOT referenced to G on purpose, called "floating" systems. The Neutral here is usually referenced and bonded to Ground at the service, but N is still considered a current carrying conductor, whereas Ground is not. No mfr of a power supply in their right mind would bond N to G inside of the unit, in fact I'm pretty sure they could not get a UL listing (or in this case just Recignition) on it if they did.

 

[SceneryDriver]

I use that power supply all the time, albeit with a different output voltage. They absolutely do not care if power is L-L or L-N. They're built for worldwide use, and their input stage are auto-ranging. Wire it up L-L if you need to with no worries.


SceneryDriver

 

[FionaZuppa]

The "L" and "N" screws should just be labeled "AC" with a small line between each one, and "120-240v" over the line in the middle.

 

[Aleman]

The supply won't care either way. But it should still be wired correctly because that would be the right way to do it.

 

[FionaZuppa]

The supply won't care either way. But it should still be wired correctly because that would be the right way to do it.

not sure what you mean, if its in US and you use 240v (residential 1ph), the "N" is what exactly? there is no "correct" way if using 240v with a connection that says "N", etc.

 

[Jraef]

not sure what you mean, if its in US and you use 240v (residential 1ph), the "N" is what exactly? there is no "correct" way if using 240v with a connection that says "N", etc.

The letter used on the terminal is not something any code requires or even addresses. You can call it "N", "Q", "42", even "Fiona"... What matters is that you connect it as per the instructions provided by the manufacturer.

 

[FionaZuppa]

The letter used on the terminal is not something any code requires or even addresses. You can call it "N", "Q", "42", even "Fiona"... What matters is that you connect it as per the instructions provided by the manufacturer.

sure, the instructions should match the letters. if you lost the instructions and the terminals said AC-------120/240-------AC would you worry about which was supposed to be the neutral "N" connection?

 

[petersonra]

most of the power supplies I see that are rated for 120 or 240 have power in terminals labeled as L and L/N in some fashion.

but I agree with the poster who said read the instructions.

 

[Jraef]

sure, the instructions should match the letters. if you lost the instructions and the terminals said AC-------120/240-------AC would you worry about which was supposed to be the neutral "N" connection?

Perfectly valid concern, and is the reason why I would label then differently if I were the designer. VFDs that accept single phase where the same situation exists often have labels that say L1/L2, then right under those are additional labels that say L and N. That's how I would do it.

But to be honest, a lot of people get confused by that system as well. There is no perfect answer if you want to make one product that can be used anywhere in the world, it's always a compromise. They compromised in a direction that does not really favor North American systems, but we likely represent a small fraction of their total market. We should probably feel lucky they don't just use Chinese characters.

But they mean well...

 

[FionaZuppa]

post #12.

using "N" anywhere on terminals that dont really care, like a full bridge rectifier, is confusing. do i really need to make sure the grounded conductor from the AC source is on a specific terminal of a bridge rectifier? nope.

"Input: AC 120v/240v 50/60Hz"

the markings between two input terminals
AC------120/240------AC
or just
AC------------AC

i think thats about as universal as you can get?

would you be confused if it looked like this (bottom supply)