Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

"Gunner" wrote: (clip) two, measured to ground..are 240..the third is 25
volts. When measured to each other..its 240
^^^^^^^^^^^^^^^^^^^^^
As long as the wiring in the shop tools is "floating," it should not matter.
Just a layman's guess: is it possible that his motors are connected wye,
with the center grounded?

For only three phase loads, ground can be anywhere on the transformers and
should be nowhere on the loads. The only reason for any ground at all is to
prevent the secondaries from floating or being accidentally energized from
the primary potential and rising dangerously high to ground. Sounds to me
like you have a corner grounded delta and the 25 volts is due to some
incidental voltage drop or stray coupling in the system.

Don Young
"Gunner" wrote in message
...
Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

On Tue, 28 Feb 2006 02:48:34 GMT, Gunner
wrote:

Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner

Cornerground Delta I could see, but that would read Zero to ground,
not 25V. And nobody I know of installs cornerground new anymore - too
many people don't realize what they are dealing with, /I'M/ not even
sure how to deal with it, and the potential for mayhem is high with a
leg that "tests dead to ground" but isn't.

The last time I hit cornerground was a 60 year old submersible well
service on a ranch. (If it works, leave it alone.)

There might be an accidental ground (possibly high-resistance) on an
ungrounded Delta that's causing the odd reading.

And that wouldn't cause the machines not to start unless they were
originally wired for a 120/240V Open Delta and has 120V controls from
one leg to neutral. If the controls are on the 'wild leg' line that
has the high-res ground on it... Get in there with an open mind and
a proper VOM - a Wiggy might send mixed messages.

Remember that it ran before the work, and doesn't now, so you need
to look at what they changed - that's a very important clue that you
sometimes don't get when you come in cold. You might have to call the
guys and find out what they did.

And Never discount anything as the cause, no matter how unlikely it
might seem at first - When I say "Nahh, they'd never do anything THAT
stupid!" that's my clue to the path I check first - because they
would, they could, they have, and they may well have again.

Don't discount that they may have screwed up somewhere along the
line and fried a fuse somewhere, and since they didn't test run the
equipment they don't know.

Or they /DO KNOW/ they opened the neutral momentarily or brushed the
wires together and sent a blast of 9,600V or 34.5KV down the 240V
secondary and fried something, but they're keeping their mouths shut -
because if they admit they screwed up, then they (or the company) will
have to pay to fix it.

In the immortal words of John Banner:
SergeantSchultz "I know Nothing, NO-THING!" /SergeantSchultz

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

Gunner,

Most schools of any size would have a 480V service. With dry packs for
the 240V. With the voltage readings you're getting on the 240V, I would
suspect one fuse out back on the 480V side. Let us know what you find out.

Don

Gunner wrote:
Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

"Gunner" wrote in message
...
Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner

I'm not Bruce, nor am I an electrician, but I can tell you for sure,
something's not right if it's delta wired. I've had three phase delta for
years-------two legs (A & C phase) to ground are each 120 v, the third leg,
the wild leg (B phase), is 208 v to ground.

Harold

On Tue, 28 Feb 2006 02:55:35 GMT, "Leo Lichtman"
wrote:


"Gunner" wrote: (clip) two, measured to ground..are 240..the third is 25
volts. When measured to each other..its 240
^^^^^^^^^^^^^^^^^^^^^
As long as the wiring in the shop tools is "floating," it should not matter.
Just a layman's guess: is it possible that his motors are connected wye,
with the center grounded?

Its possible, or the control circuits are wired to the 25 volt leg and
ground..pretty common.

Ill go check it out towards the end of the week

25 volts??????

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

On Tue, 28 Feb 2006 06:52:29 GMT, Don Murray
wrote:

Gunner,

Most schools of any size would have a 480V service. With dry packs for
the 240V. With the voltage readings you're getting on the 240V, I would
suspect one fuse out back on the 480V side. Let us know what you find out.

Don

If a fuse in the main was blown..why would it read 240 from leg to leg
on L1/L2/L3 ?

My first reaction before he told me it was 240 across each other..was
a dead leg with the 25 volts inducted...but????

Gunner


Gunner wrote:
Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

On Tue, 28 Feb 2006 08:56:46 GMT, Gunner wrote:

On Tue, 28 Feb 2006 06:52:29 GMT, Don Murray
wrote:

Gunner,

Most schools of any size would have a 480V service. With dry packs for
the 240V. With the voltage readings you're getting on the 240V, I would
suspect one fuse out back on the 480V side. Let us know what you find out.

Don

If a fuse in the main was blown..why would it read 240 from leg to leg
on L1/L2/L3 ?

My first reaction before he told me it was 240 across each other..was
a dead leg with the 25 volts inducted...but????

Gunner


Gunner wrote:
Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner


An un-earthed delta connection with a neon indicator bulb wired between one
phase and earth? (I don't know why, but some of the weird electrical systems
you chaps seem to have would scare the crap out of me :-)


Mark Rand
RTFM


"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

Maybe the main winding fused out - but the boost/buck transformer was still in line.
The primary of that third phase - the secondary was mostly wire ?

I'd get someone on it soon - might be a serious power drop somewhere.
Or something on the line - an elevator to the school (freight) doesn't work and no
one knows it.


Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder



Gunner wrote:
On Tue, 28 Feb 2006 06:52:29 GMT, Don Murray
wrote:


Gunner,

Most schools of any size would have a 480V service. With dry packs for
the 240V. With the voltage readings you're getting on the 240V, I would
suspect one fuse out back on the 480V side. Let us know what you find out.

Don


If a fuse in the main was blown..why would it read 240 from leg to leg
on L1/L2/L3 ?

My first reaction before he told me it was 240 across each other..was
a dead leg with the 25 volts inducted...but????

Gunner


Gunner wrote:

Buddy of mine is a shop teacher over at the Pasadena school district.
He claims a number of his machine tools wont start..so I had him
checking the voltages on the 3 ph wiring.

two, measured to ground..are 240..the third is 25 volts. When measured
to each other..its 240

Delta I belive..but...25 volts???? He called in the schools
electrician..and he claims they installed new transformers during
Christmas break..wired delta and that 25 volt leg is normal.

110 I can see..but ....wtf???

Gunner



"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3




"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences."
- Proverbs 22:3

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