Electronics

ini-tech · Joined: 05 Jul 2006 Posts: 2 Location: California

Hello,

I design a machine that requires 120V 50/60hz 15 Amp outlet. Our system draws about 8 amps when fully loaded.

For a standard residential power outlet there are three wires into the PDU
Typically PE (ground)= 0, L (line) = 120 V AC, N (neutral)= 0 V AC.

A customer of mine in Korea is supplying power like this:

PE (ground)= 0, L (line) = 60 V AC, N (neutral)= 60 V AC. at 180 degrees out of phase.

The main power line into our system is distributed to each electrical components by using an "Isobar12Ultra" PDU; power distribution unit from Tripplite.

Isobar12Ultra surge suppressor info:
http://www.tripplite.com/products/product.cfm?productID=114

The Fault LED is comes on when it is used at the Korea facility. Why?

All the components that receive power from the PDU seem to work fine; Is any harm being done?

When running the system in that Korean facility, occasionally the circuit breaker trips at random times. Any reason why this would happen? The system draws the same load as always.

Thanks,
Marc

neon · Joined: 25 Feb 2006 Posts: 585

Did you design your machine to operate at 60 volts AC as you say for your korean costumer that is is trying to use a machine with 120v AC 8 Amps power input requirement? All being equal the same power will be required at the korean facility if 60 v is the source then 16 amps must be supplied to satisfy power. Unless of course as I suspect you have made an error by by saying 60v as opposed to 60 hz. And i don't think that phase matter since it goes around full circle. And how does he knows is out of phase with reference to whar? I think we need more correct information to help you further. Take care

ini-tech · Joined: 05 Jul 2006 Posts: 2 Location: California

neon,

The machine is designed to be used in the USA with a standard 120V outlet. No changes have been made to the machine

The Korean customer supplies power with 60Volts at the line and 60Volts at Neutral; Line and Neutral are 180 degrees out of phase from each other...so the total Voltage of the system is still 120V. Neutral is not zero like it is here in USA.

We are told by the Korean customer that their power supply is designed this way... 180deg out of phase. And we measured ground and line to confirm that this is correct.

The machine runs fine...just wondering if this is damaging something and why the PDU power distribution with surge suppression had a Fault LED on?

Also wondering why the breaker on the PDU trips occasionally?

Thanks for you help

ini-tech

wa4dc · Joined: 15 Sep 2006 Posts: 1 Location: Tampa, FL

Hey there, It seems to me that the tech that installed the connections to provide the required 120vac probably is unfamilar with the transformer connection practices common to the USA. In short if I were to use a transformer to change, say 480vac to 120vac, and I did not connect one of the output leads of the transformer secondary to ground. I would expect to measure at each lead to ground- 60vac. Given that there is not a drawing of the transformer supplied by the end user. I would also want to question the KVA rating, as well as any other connections to this transformer as additional loads on this xfrmer may cause your output to react. Normally the xfrmer for such use would be specified in KVA rating, and the connection drawing would be supplied to the user. Hope this helps.
_________________
wa4dc, Bill

Tuber · Joined: 06 Mar 2007 Posts: 3

In the US, nuetral is connected to ground. To avoid all risk, use a 1 to 1 isolation transformer. Connect the input across the foreign lines. Carry the ground through to one side of the output and the US ground. The grounded side of the output is nuetral (white). The ground is ground (green or bare copper). The other side of the output is the line (black or red). Generally, you need to avoid a floating system, no ground reference, that can build static charge and suddenly ionize a path to ground.

neon · Joined: 25 Feb 2006 Posts: 585

I think your ac circuit protection are being taxed as you say they are tied to common but in korea it is not so causing surges and false triggering because of incompatablilty. I Bet you your unit will run here whithout problems. You should address this problem it will never go away.

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