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#200680 04/14/11 12:12 AM
Joined: Apr 2003
Posts: 362
Member
Had my first dealings with 2 phase. Was disconnecting a machine and wanting make sure all the leads are identified, I started going over everything. At first I thought the 4 pole disconnect may have had a nutreal being disconnected. But wait there is no 110v on this machine. readings to ground were all over, and there was 2 sets of 240v. Aaaa wow! 2 phase. I thought it was a urban legend! Sure as could be a 3 phase to 2 phase 50kw trans. What I have learned to be a Scot Trans. comments welcome:)

Ob


Choose your customers, don't let them choose you.
Obsaleet #200690 04/14/11 09:17 AM
Joined: Apr 2002
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The only and last place I saw 2 phas was in Philadelphia, many, many years ago. Working with one of the 'old timers', and I don't remember much of it today.



John
Obsaleet #200715 04/16/11 02:14 PM
Joined: Feb 2002
Posts: 2,233
H
Member
John,

The strangest voltage system I ever saw was in Jersey City. There were 3 phase legs going to a machine. You got 240 volts between each phase leg. On 2 of the phase legs you got 120 volt and on the third leg you got zero voltage to ground. There was no neutral for these machines. I was told that it was a very old style system.

Obsaleet #200717 04/16/11 02:22 PM
Joined: Feb 2002
Posts: 2,233
H
Member
I thought that true 2 phase was there were 2 phase legs and 2 neutrals. 1 neutral for each phase leg.

Obsaleet #200720 04/16/11 02:55 PM
Joined: Jul 2004
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G
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Harold, are you sure that wasn't 240v to ground on the other 2 legs?

That would be corner grounded delta.


Greg Fretwell
Obsaleet #200722 04/16/11 07:07 PM
Joined: Apr 2003
Posts: 362
Member
Harold,
Thats about right, except voltage to ground was more like 135v, 120v, 180v, 0v. approx voltages? I got on the phone asap when I knew I wasn't in Kansas anymore.



Ob


Choose your customers, don't let them choose you.
Obsaleet #200738 04/17/11 02:18 PM
Joined: Feb 2002
Posts: 2,233
H
Member
Greg,

No, I believe it was 120-125 volts to ground and 240 between legs. The 3rd leg was zero volts to ground. Even my old boss found this wiring system to be real weird. He used to work for Bendix and they made airplane parts here in NJ. They use to work with all sorts of wacky voltage and freq. in their factory. They even had one system that was 400 Mz I believe. It was for satellites or something.

Obsaleet #200739 04/17/11 02:21 PM
Joined: Feb 2002
Posts: 2,233
H
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Ob,

As I said to Greg, I believe it was around 125 volts. It as many years ago and my memory isn't what it used to be. I just started as an apprentice with the old boss, so that would have been around 1977. Plus I only saw this type of system once in all the years I have been doing electrical work. I was more a resi-com type of electric, not much into heavy industrial.

Obsaleet #200742 04/17/11 03:02 PM
Joined: Jul 2004
Posts: 9,667
Likes: 6
G
Member
I am not sure how you can have 240 volts from phase to phase, one phase that looks be grounded and not have 240 to ground. It may be impedance grounding on that corner and a low impedance measuring tool (wiggy?)


Greg Fretwell
Obsaleet #200763 04/18/11 10:16 AM
Joined: Feb 2002
Posts: 2,233
H
Member
Greg,

Like I said, it was a long time ago. I maybe mistaken. If I see my old boss again, I will ask him if he remembers. He still works around here but not as much as he used to.

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