On Wed, 28 Jan 2009 01:59:03 GMT, (dan) wrote:

What's that Lassie? You say that David Lesher fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Tue, 27 Jan 2009 05:55:46 +0000 (UTC):

I know of no 3-phase Kil-o-Watts, so do this. Find a surplus 3-phase
power meter, and mount a meter box on a board. Put it in the motor
supply leg, note the time/date/meter reading, and let it got for 5 hours
or a day.

That's the best way of finding the actual usage.

Thanks, but that's a bit farther than I want to go.

I think I will just assume full nameplate amps when loaded and
multiply by the duty cycle.

BTW, I had been wrong on the voltage all along. It's being fed from
one of the 460V panels.

And if yours is a constant run unloader system (usually used on big
industrial piston compressors, and most screw type units) you can pop
on a Clamp Amp to estimate the current under load versus the current
when idling to get a discount factor for that.

The ammeter doesn't care about 230V vs 460V, but your fingers sure
do, so be REAL Careful with the covers open and the unit energized.
460V will knock your ass across the room if it gets half a chance.

I'd suspect that the current will drop to about 50% of Nameplate FLA
when unloaded, but even lower is quite possible.

You aren't going to be able to tell true power draw without a way to
read power factor (inductive lag, capacitive lead), and the metering
gear to find that out is going to be real spendy. Guesstimate.

-- Bruce --

What's that Lassie? You say that Bruce L. Bergman fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Tue, 27 Jan 2009 23:31:55 -0800:

(dan) wrote:

I think I will just assume full nameplate amps when loaded and
multiply by the duty cycle.

BTW, I had been wrong on the voltage all along. It's being fed from
one of the 460V panels.


And if yours is a constant run unloader system (usually used on big
industrial piston compressors, and most screw type units) you can pop
on a Clamp Amp to estimate the current under load versus the current
when idling to get a discount factor for that.

It is, and I did. 15A loaded 10A un-loaded.

The ammeter doesn't care about 230V vs 460V, but your fingers sure
do, so be REAL Careful with the covers open and the unit energized.
460V will knock your ass across the room if it gets half a chance.

Hell, 220V scares me so much, I've never been bit by it. 110V stings
plenty, thank you. If I had known it was 460v I might not have
bothered taking a reading. But there was plenty of room in the
control panel and the line in wires were easy to get the clamp around.

I'd suspect that the current will drop to about 50% of Nameplate FLA
when unloaded, but even lower is quite possible.

I thought so too. When it wasn't, I thought I should ask here.

You aren't going to be able to tell true power draw without a way to
read power factor (inductive lag, capacitive lead), and the metering
gear to find that out is going to be real spendy. Guesstimate.

Yep. That seems to be the consensus. I'm going to estimate high by
assuming nameplate FLA. That and the duty cycle should be close
enough.

Thanks.

--

Dan H.

On Jan 29, 7:09*pm, (dan) wrote:
What's that Lassie? You say that Bruce L. Bergman fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Tue, 27 Jan 2009 23:31:55 -0800:

(dan) wrote:

I think I will just assume full nameplate amps when loaded and
multiply by the duty cycle.

BTW, I had been wrong on the voltage all along. *It's being fed from
one of the 460V panels.

*And if yours is a constant run unloader system (usually used on big
industrial piston compressors, and most screw type units) you can pop
on a Clamp Amp to estimate the current under load versus the current
when idling to get a discount factor for that.

It is, and I did. *15A loaded 10A un-loaded.



*The ammeter doesn't care about 230V vs 460V, but your fingers sure
do, so be REAL Careful with the covers open and the unit energized.
460V will knock your ass across the room if it gets half a chance.

Hell, 220V scares me so much, I've never been bit by it. *110V stings
plenty, thank you. *If I had known it was 460v I might not have
bothered taking a reading. *But there was plenty of room in the
control panel and the line in wires were easy to get the clamp around.



*I'd suspect that the current will drop to about 50% of Nameplate FLA
when unloaded, but even lower is quite possible.

I thought so too. *When it wasn't, I thought I should ask here.



*You aren't going to be able to tell true power draw without a way to
read power factor (inductive lag, capacitive lead), and the metering
gear to find that out is going to be real spendy. *Guesstimate.

Yep. *That seems to be the consensus. *I'm going to estimate high by
assuming nameplate FLA. *That and the duty cycle should be close
enough.

Thanks.

--

Dan H.

Dan,
You do understand that 240 volts ( in the USA) is erally only two 120
volt circuits?
Touching either wire, only gives you 120 volts, to ground.
480 volts, is really 277 volts to ground for any one of the three
wires. 480 volts between any two wires.

Now, 277 volts will not be anything I ever want to experience!

"Half-Nutz" wrote in message
...

Dan,
You do understand that 240 volts ( in the USA) is erally only two 120
volt circuits?
Touching either wire, only gives you 120 volts, to ground.
480 volts, is really 277 volts to ground for any one of the three
wires. 480 volts between any two wires.

Now, 277 volts will not be anything I ever want to experience!

-----------------------------------------------------------------------------------------------\\

Are you sure that is true for all 480v systems in the US?

I think all three of my phases measure 480 to ground, and 480 phase to
phase.

"Edwin Lester" wrote:


-----------------------------------------------------------------------------------------------\\

Are you sure that is true for all 480v systems in the US?

I think all three of my phases measure 480 to ground, and 480 phase to
phase.


Not physically (as in physics) (or electrically) possible.
To give you a geometric analogy, what you are saying is equivalent to.

Take a piece of paper, put 3 dots on it, that are all exactly the same
distance from a common 4th dot, and that same distance from each
other. YOu can do it with two dots,[They make an equilateral triangle]
but not 3 dots in a flat plane.


jk

On Thu, 29 Jan 2009 19:07:23 -0800, jk wrote:
"Edwin Lester" wrote:

Are you sure that is true for all 480v systems in the US?

I think all three of my phases measure 480 to ground, and 480 phase to
phase.


Not physically (as in physics) (or electrically) possible.
To give you a geometric analogy, what you are saying is equivalent to.

Take a piece of paper, put 3 dots on it, that are all exactly the same
distance from a common 4th dot, and that same distance from each
other. YOu can do it with two dots,[They make an equilateral triangle]
but not 3 dots in a flat plane.

I suppose you /could/ wire the secondaries on the service
transformer (transformers plural if you use three single-phase cans on
an old style rack) corner-grounded, but nobody does - the ONLY place
I've seen corner-ground service is a 240V 3Ph well service.

Imagine your triangle made up of the three transformer secondaries
in a ring, the three points of the corner are where you attach the 3
motor phases. You run the power to the well pump contactor through
three fuses, too.

But you take one corner and also attach the local earth ground, and
when it gets to the well panel you bond it to ground there too.
Suddenly you have two leads 240V to ground and one 0V to ground - but
still 240V phase-to-phase.

It's not very popular, because IMNSHO they aren't safe to allow
untrained ranch hands around - people see it's Grounded and simply
don't stop to think it can also be a current carrying conductor.

I don't install 'em, I just fix 'em. And I put a Big Warning Note
on both the outside and inside of the cover in permanent paint marker,
in case one of those untrained persons starts poking around inside -
then they can't say I didn't warn them.

-- Bruce --

What's that Lassie? You say that Half-Nutz fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Thu, 29 Jan 2009 17:15:41 -0800 (PST):


Dan,
You do understand that 240 volts ( in the USA) is erally only two 120
volt circuits?

YEp, got that.

Touching either wire, only gives you 120 volts, to ground.



480 volts, is really 277 volts to ground for any one of the three
wires. 480 volts between any two wires.

Now, 277 volts will not be anything I ever want to experience!

Me neither.

--

Dan H.

On Sat, 31 Jan 2009 06:01:21 GMT, (dan) wrote:

What's that Lassie? You say that Half-Nutz fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Thu, 29 Jan 2009 17:15:41 -0800 (PST):


Dan,
You do understand that 240 volts ( in the USA) is erally only two 120
volt circuits?

YEp, got that.

Touching either wire, only gives you 120 volts, to ground.



480 volts, is really 277 volts to ground for any one of the three
wires. 480 volts between any two wires.

That 277V to ground is only a certainty if they use a Wye connection
secondary and ground the center point.

If they have Delta connection and the ground is floating, or it's
corner grounded, or other odd stuff - all bets are off.

Now, 277 volts will not be anything I ever want to experience!

Me neither.

That's why I spent a Sawbuck on a set of lineman gloves, liners and
gauntlets.

I'll work on it hot only as far as opening the door and carefully
diagnosing what's wrong, I am NOT going to try any hot repairs.

Discretion is the better part of going home at quitting time.

-- Bruce --

"jk" wrote in message
news
"Edwin Lester" wrote:


-----------------------------------------------------------------------------------------------\\

Are you sure that is true for all 480v systems in the US?

I think all three of my phases measure 480 to ground, and 480 phase to
phase.


Not physically (as in physics) (or electrically) possible.
To give you a geometric analogy, what you are saying is equivalent to.

Take a piece of paper, put 3 dots on it, that are all exactly the same
distance from a common 4th dot, and that same distance from each
other. YOu can do it with two dots,[They make an equilateral triangle]
but not 3 dots in a flat plane.


Just double checked. My system show 480 phase to ground on two phases, and 0
on the third. All phases measure 480 phase to phase.

"Edwin Lester" wrote:




Just double checked. My system show 480 phase to ground on two phases, and 0
on the third. All phases measure 480 phase to phase.


So then what you have is a corner grounded delta. Unusual, but not
unknown. It ias also possible you have an ungrounded delta, with a
ground fault on one leg. [Almost the same difference really]

jk

"jk" wrote in message
...
"Edwin Lester" wrote:




Just double checked. My system show 480 phase to ground on two phases, and
0
on the third. All phases measure 480 phase to phase.


So then what you have is a corner grounded delta. Unusual, but not
unknown. It ias also possible you have an ungrounded delta, with a
ground fault on one leg. [Almost the same difference really]

jk

IIRC, my system is preferred for motor loads and other such high amp
equipment, and the 277 flavor was more useful if a LOT of 277v lighting was
required.