I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?

On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Tue, 12 Jan 2016 09:57:33 -0800 (PST), rangerssuck
wrote:

I'm doing some work in an older factory - MANY electricians have had their hands in this place.
They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase
230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching
while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation,
but surely there's a better way? What if this was a big piece of equipment, or something that would do damage
if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out),
but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?

Bernie would demand a fixed minimum income for electricians so that
they'd have more free time to bone up on the latest developments in 3
phase wiring.

Hillary would ask her donors for enough money to fund 6 national polls
to see what she should do.

The Donald would blame the problem on China and Mexico and say that he
knows the secret and if he was in charge all wiring colors would be
very very very correct and the most uniform in the history of
electricity. If pressed sufficiently he would produce a rummy former
electrician who would recommend a three black wire national standard.

We here at the Oregon occupation think you should wait until dark, cut
the locks at a better location and move in there.

O.R.E.O.s

PS Why do you need a switch anyway? Save the money and join the
revolution. Sooner or later we'll take over a VFD distributor. Then
all you'd have to do is read a manual and press some buttons to change
direction.

On 12/01/16 17:57, rangerssuck wrote:
I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?
You want a phase rotation tester see
http://www.test-meter.co.uk/phase-rotation-testers/ . I've never used
one but have spoken to electricians that have, a fairly common piece of
kit in the toolbox if you work with 3 phase machinery regurlarly.

On Tuesday, January 12, 2016 at 1:10:01 PM UTC-5, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Thanks. I just ordered one.

On Tuesday, January 12, 2016 at 2:13:24 PM UTC-5, David Billington wrote:
On 12/01/16 17:57, rangerssuck wrote:
I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?
You want a phase rotation tester see
http://www.test-meter.co.uk/phase-rotation-testers/ . I've never used
one but have spoken to electricians that have, a fairly common piece of
kit in the toolbox if you work with 3 phase machinery regurlarly.

There will be one in my toolbox (well, tool bag, actually) tomorrow.

On Tuesday, January 12, 2016 at 1:25:23 PM UTC-5, wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST), rangerssuck
wrote:

I'm doing some work in an older factory - MANY electricians have had their hands in this place.
They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase
230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching
while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation,
but surely there's a better way? What if this was a big piece of equipment, or something that would do damage
if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out),
but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?

Bernie would demand a fixed minimum income for electricians so that
they'd have more free time to bone up on the latest developments in 3
phase wiring.

Hillary would ask her donors for enough money to fund 6 national polls
to see what she should do.

The Donald would blame the problem on China and Mexico and say that he
knows the secret and if he was in charge all wiring colors would be
very very very correct and the most uniform in the history of
electricity. If pressed sufficiently he would produce a rummy former
electrician who would recommend a three black wire national standard.

We here at the Oregon occupation think you should wait until dark, cut
the locks at a better location and move in there.

O.R.E.O.s

PS Why do you need a switch anyway? Save the money and join the
revolution. Sooner or later we'll take over a VFD distributor. Then
all you'd have to do is read a manual and press some buttons to change
direction.

If we could just take over the national power grid, I could use an app on my phone to change the rotation on every three-phase motor in the country. That would be very cool.

I'd come to Oregon to join the mob^H^H^Hrevolution, but I'm busy standing guard here in New Jersey. If Christie gets any closer to be taken seriously, we plan to blockade all of the ball fields where his kids play so he won't be able to land his helicopter. Can you run a campaign from a helicopter that can't land? Surely there are papers that must be signed.

On Tue, 12 Jan 2016 11:40:19 -0800 (PST), rangerssuck
wrote:

On Tuesday, January 12, 2016 at 1:10:01 PM UTC-5, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Thanks. I just ordered one.

You took the easy way out? Coward! Why can't anyone understand that
the best solution to every problem is revolution?

O.R.E.O.s

PS What libtard nonsense will you spout next, that you pay for your
own health care?

On Tue, 12 Jan 2016 11:49:20 -0800 (PST), rangerssuck
wrote:

On Tuesday, January 12, 2016 at 1:25:23 PM UTC-5, wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST), rangerssuck
wrote:

I'm doing some work in an older factory - MANY electricians have had their hands in this place.
They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase
230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching
while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation,
but surely there's a better way? What if this was a big piece of equipment, or something that would do damage
if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out),
but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?

Bernie would demand a fixed minimum income for electricians so that
they'd have more free time to bone up on the latest developments in 3
phase wiring.

Hillary would ask her donors for enough money to fund 6 national polls
to see what she should do.

The Donald would blame the problem on China and Mexico and say that he
knows the secret and if he was in charge all wiring colors would be
very very very correct and the most uniform in the history of
electricity. If pressed sufficiently he would produce a rummy former
electrician who would recommend a three black wire national standard.

We here at the Oregon occupation think you should wait until dark, cut
the locks at a better location and move in there.

O.R.E.O.s

PS Why do you need a switch anyway? Save the money and join the
revolution. Sooner or later we'll take over a VFD distributor. Then
all you'd have to do is read a manual and press some buttons to change
direction.

If we could just take over the national power grid, I could use an app on my phone to change
the rotation on every three-phase motor in the country. That would be very cool.

I'd come to Oregon to join the mob^H^H^Hrevolution, but I'm busy standing guard here
in New Jersey. If Christie gets any closer to be taken seriously, we plan to blockade all
of the ball fields where his kids play so he won't be able to land his helicopter. Can you run
a campaign from a helicopter that can't land? Surely there are papers that must be signed.

Hopefully Trump will win the nomination. Which would free up Christie
to join the revolution. Lots of room for his chopper here. I bet he
knows how to block the bridge to Oregon.

O.R.E.O.s

PS Plus, if we run out of food at the compound, Christie's thighs
alone would last us a week.

They sell phase rotation detectors, like this one:

http://www.amazon.com/Extech-480400-.../dp/B001AGTXY2

On 2016-01-12, rangerssuck wrote:
I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?

On 2016-01-12, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

That works for that. We had a big DC power supply 50 VDC at
*lots* of current which was fed from three phase, and the manual warned
that connecting it backwards would instantly destroy the warranty (and
the device).

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

I did not know where to buy one, but I was able to find out how
to *make* one using neon lamps, resistors and capacitors, IIRC.

The power supply survived. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Tue, 12 Jan 2016 09:57:33 -0800 (PST), rangerssuck
wrote:

I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?
Well, if you know which outlets run it backwards it should be pretty
simple. Just switch any two wires. If you want a "simple as a sack of
rocks" test, just grab a small 3 phase motor and lable the wires - use
it as a test motor to determine phase rotation.

On Tue, 12 Jan 2016 11:40:19 -0800 (PST), rangerssuck
wrote:

On Tuesday, January 12, 2016 at 1:10:01 PM UTC-5, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Thanks. I just ordered one.
Just over ten bucks on E-Bay

On Tuesday, January 12, 2016 at 8:28:47 PM UTC-5, DoN. Nichols wrote:


I did not know where to buy one, but I was able to find out how
to *make* one using neon lamps, resistors and capacitors, IIRC.


Enjoy,
DoN.

I was curious and searched the internet.

http://webspace.webring.com/people/g...se/3phase.html

You could use two 120 volt lamps in series for each 240 volt lamp. So home free if you have a suitable capacitor.

Dan

On 2016-01-13, wrote:
On Tuesday, January 12, 2016 at 8:28:47 PM UTC-5, DoN. Nichols wrote:


I did not know where to buy one, but I was able to find out how
to *make* one using neon lamps, resistors and capacitors, IIRC.


Enjoy,
DoN.

I was curious and searched the internet.

http://webspace.webring.com/people/g...se/3phase.html

You could use two 120 volt lamps in series for each 240 volt lamp. So
home free if you have a suitable capacitor.

Yes -- that is one version. I do see potential problems in
it, however:

================================================== ====================
You'll need 2 incandescent bulbs with a rated voltage equal to the line
voltage,

[ ... ]

Measure the ohmic resistance R of the bulbs. The condition to fulfill is
that the three reactances must be equal, so the reactive capacitance
should be:
================================================== ====================

The problem is that incandescent lamps have a resistance which
is quite low when cold (the condition under which you are measuring it),
and quite a bit higher when hot. (Easily an order of magnitude change
from cold to fully lit.)

But -- it may get you close enough for the thing to work.

The thing that amazes me is that the makers of the power supply
did not build in a simple phase sequence circuit to keep you from
switching it on if the phase is reversed. :-)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 13 Jan 2016 03:32:00 GMT, "DoN. Nichols"
wrote:

On 2016-01-13, wrote:
On Tuesday, January 12, 2016 at 8:28:47 PM UTC-5, DoN. Nichols wrote:


I did not know where to buy one, but I was able to find out how
to *make* one using neon lamps, resistors and capacitors, IIRC.


Enjoy,
DoN.

I was curious and searched the internet.

http://webspace.webring.com/people/g...se/3phase.html

You could use two 120 volt lamps in series for each 240 volt lamp. So
home free if you have a suitable capacitor.

Yes -- that is one version. I do see potential problems in
it, however:

================================================== ====================
You'll need 2 incandescent bulbs with a rated voltage equal to the line
voltage,

[ ... ]

Measure the ohmic resistance R of the bulbs. The condition to fulfill is
that the three reactances must be equal, so the reactive capacitance
should be:
================================================== ====================

The problem is that incandescent lamps have a resistance which
is quite low when cold (the condition under which you are measuring it),
and quite a bit higher when hot. (Easily an order of magnitude change
from cold to fully lit.)

But -- it may get you close enough for the thing to work.

You don't measure the resistance of the bulb. You calculate it from
the wattage and the voltage.

The thing that amazes me is that the makers of the power supply
did not build in a simple phase sequence circuit to keep you from
switching it on if the phase is reversed. :-)

Enjoy,
DoN.

On 13 Jan 2016 01:27:48 GMT
"DoN. Nichols" wrote:

On 2016-01-12, Leon Fisk wrote:

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

That works for that. We had a big DC power supply 50 VDC at
*lots* of current which was fed from three phase, and the manual warned
that connecting it backwards would instantly destroy the warranty (and
the device).

This was a somewhat new plastic injection machine. I say somewhat new
because it was rolled over onto its side when the riggers were bringing
it in. Customer was none to happy with that. So the machine already had
a "story"...

Our obvious concern was that the machine had a good sized hydraulic
pump on it, run by a three-phase motor. Hydraulic pumps don't always
like to be spun in the opposite direction... We got away with it, at
least long enough to determine direction of rotation. Even if we had had
a direction determining meter/device I don't know how we would have
correlated it with the machine wiring at the time...

I remember whole shops getting thrown out of whack, rotation gone
backwards after the power company had done work somewhere on the
incoming power lines down the street. Oops!

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Tuesday, January 12, 2016 at 10:46:12 PM UTC-5, Clare wrote:
On 13 Jan 2016 03:32:00 GMT, "DoN. Nichols"
wrote:

On 2016-01-13, wrote:
On Tuesday, January 12, 2016 at 8:28:47 PM UTC-5, DoN. Nichols wrote:


I did not know where to buy one, but I was able to find out how
to *make* one using neon lamps, resistors and capacitors, IIRC.


Enjoy,
DoN.

I was curious and searched the internet.

http://webspace.webring.com/people/g...se/3phase.html

You could use two 120 volt lamps in series for each 240 volt lamp. So
home free if you have a suitable capacitor.

Yes -- that is one version. I do see potential problems in
it, however:

================================================== ====================
You'll need 2 incandescent bulbs with a rated voltage equal to the line
voltage,

[ ... ]

Measure the ohmic resistance R of the bulbs. The condition to fulfill is
that the three reactances must be equal, so the reactive capacitance
should be:
================================================== ====================

The problem is that incandescent lamps have a resistance which
is quite low when cold (the condition under which you are measuring it),
and quite a bit higher when hot. (Easily an order of magnitude change
from cold to fully lit.)

But -- it may get you close enough for the thing to work.

You don't measure the resistance of the bulb. You calculate it
from the wattage and the voltage.

DMM's (digital meters) can measure the loads of light bulbs. Now, a digital oscilloscope is quite a leap from something like an analog oscilloscope (like the one I think rangerss was talking about). Digital oscilloscopes are more accurate in measurement than analog ones.

On 01/13/2016 2:08 PM, wrote:
....

DMM's (digital meters) can measure the loads of light bulbs. Now, a
digital oscilloscope is quite a leap from something like an analog
oscilloscope (like the one I think rangerss was talking about).
Digital oscilloscopes are more accurate in measurement than analog
ones.

Not necessarily; they're limited by both the A/D resolution (many are,
after all, only 8-bit) and even Tektronix quotes only 3% vertical
measurement accuracy for many of their scopes.

The digital 'scope also is somewhat susceptible to the same issues as
the DMM in comparison to an analog--the extremely high input impedance
can give rise to the same "phantom" signals if the DUT isn't loaded.

DSOs have advantages of course, otherwise they'd have not taken over
market share but they're mostly in the convenience of actual readout and
the ability to do advanced signal processing on the measurement
directly, _NOT_ so much that they're fundamentally any more accurate.

--

On Wed, 13 Jan 2016 14:33:01 -0600, dpb wrote:

On 01/13/2016 2:08 PM, wrote:
...

DMM's (digital meters) can measure the loads of light bulbs. Now, a
digital oscilloscope is quite a leap from something like an analog
oscilloscope (like the one I think rangerss was talking about).
Digital oscilloscopes are more accurate in measurement than analog
ones.

Not necessarily; they're limited by both the A/D resolution (many are,
after all, only 8-bit) and even Tektronix quotes only 3% vertical
measurement accuracy for many of their scopes.

The digital 'scope also is somewhat susceptible to the same issues as
the DMM in comparison to an analog--the extremely high input impedance
can give rise to the same "phantom" signals if the DUT isn't loaded.

DSOs have advantages of course, otherwise they'd have not taken over
market share but they're mostly in the convenience of actual readout and
the ability to do advanced signal processing on the measurement
directly, _NOT_ so much that they're fundamentally any more accurate.

I tried one for a spark-flash photo project around 15 years ago. It
couldn't display the fast transients. I gave it back and went back to
analog.

-
Ed Huntress

I had students with a Can manufacturing company that got a big
machine that was 3-phase all over it. the motors had to start
in the correct direction the first time. I seem to recall something
like gear train destruction would occur. I luckly found a Neon lamp
tester in a magazine that fit the bill. This was in the early 70's.

Martin

On 1/12/2016 12:09 PM, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester

On Thursday, January 14, 2016 at 11:46:03 PM UTC-5, Martin Eastburn wrote:
I had students with a Can manufacturing company that got a big
machine that was 3-phase all over it. the motors had to start
in the correct direction the first time. I seem to recall something
like gear train destruction would occur. I luckly found a Neon lamp
tester in a magazine that fit the bill. This was in the early 70's.

Martin

On 1/12/2016 12:09 PM, Leon Fisk wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST)
rangerssuck wrote:

snip
How do "real" electricians identify the phase connections when they can't count on the wire colors?

I was only an "apprentice" but 30 years ago we just hooked up the
equipment and noted the direction. Once we had a really expensive
plastic injection machine. That was a bit nerve wracking. We had one
of us watch a motor and the other give it a quick bump on/off. We had it
wrong of course, switched the wires around, it worked okay yet...

Nowadays you can buy rotation testers for not so much. I would just buy
one if I was still working with that kind of stuff. For instance:

http://www.amazon.com/s/ref=nb_sb_no...3+phase+tester


This http://www.byramlabs.com/store/produ...ion%20Te ster is the real deal, but Greenlee had the 5774 and probably has a replacement that can do the job as well. You can connect the motor and turn it by hand and it will tell you what phase you need to get the motor to turn that way. Then you connect it to the line and it will tell you what phase you have.

Being that those things aren't at all cheap, I went with one of the $20 units from amazon that just displays the phase of the power line. I'll test all the outlets in question and change the fewest possible to get them all the same. This will probably be early next week.

On Tuesday, January 12, 2016 at 8:32:56 PM UTC-5, Clare wrote:
On Tue, 12 Jan 2016 09:57:33 -0800 (PST), rangerssuck
wrote:

I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

Well they think that's a great idea. And I should go up there and make sure they do it right.

So, I COULD identify the correct wiring by simply by plugging in the motor and checking for correct rotation, but surely there's a better way? What if this was a big piece of equipment, or something that would do damage if the motor turned the wrong way?

I COULD hook up my oscilloscope (and it always impresses the hell out of them when I pull that out), but is there an even better way? How do "real" electricians identify the phase connections when they can't count on the wire colors?

[just to get back on the off topic]
How would Bernie, Hillary and Donald do it? How would they do it in Oregon?
Well, if you know which outlets run it backwards it should be pretty
simple. Just switch any two wires. If you want a "simple as a sack of
rocks" test, just grab a small 3 phase motor and lable the wires - use
it as a test motor to determine phase rotation.

Unfortunately, I don't know which outlets are forwards and which are backwards. And while you'd think the customer would have kept track...Dumber than a sack of hammers comes to mind.

There are actually meters for this that have a tiny motor in them to display the direction. I like that, but I've already received the LED thing from Amazon.

On 2016-01-15, Martin Eastburn wrote:
I had students with a Can manufacturing company that got a big
machine that was 3-phase all over it. the motors had to start
in the correct direction the first time. I seem to recall something
like gear train destruction would occur. I luckly found a Neon lamp
tester in a magazine that fit the bill. This was in the early 70's.

Such things should be protected by "three phase rotation relays".

i

Tell the Germans back in the 70's. Maybe they weren't invented yet.

We had the electrician (we is loose - county school I live in county)
wire up a very large and powerful CNC umpteen axis machine and blew up
the campus transformer! That is a big transformer for a college.

Took two days to get one installed. Department head was axed. Had to
do it to someone. (He was a friend).

A meter would have detected the shorting neutral/gnd to a hot and a hot
to a neutral ground.

Lots of stuff had to be replaced on the new monster mill. The regional
companies that supported the class - feeding them programmers and users
They stepped up and paid for the burnt motors and such.

The electrician for the school, a Master, blew it and others caught it.

I think to boot it, the voltage was from the wrong panel and was the
wrong voltage as well.

I worked in a R&D lab with large machines and we had 50, 60 and 400 Hz
power buses. The 50 and 400 was generated on site. You can bet we had
stuff labled and checked it when a bus wasn't being used.

Martin

On 1/15/2016 2:50 PM, Ignoramus475 wrote:
On 2016-01-15, Martin Eastburn wrote:
I had students with a Can manufacturing company that got a big
machine that was 3-phase all over it. the motors had to start
in the correct direction the first time. I seem to recall something
like gear train destruction would occur. I luckly found a Neon lamp
tester in a magazine that fit the bill. This was in the early 70's.

Such things should be protected by "three phase rotation relays".

i

On Tuesday, January 12, 2016 at 12:57:36 PM UTC-5, rangerssuck wrote:
I'm doing some work in an older factory - MANY electricians have had their hands in this place. They called me today with a problem:

They have a piece of equipment they have been moving from room to room. It has a 3-phase 230V motor (about 1 HP). In some rooms it runs backwards, so they have been swapping wires inside the motor junction box.

They asked me whether I could add a reversing switch, with a lockout to prevent it from switching while it's running. Well, yes I could do that, but why don't they just rewire the outlets so they're all the same?

So, I was at the factory today to fix something completely unrelated, but I threw the phase detector in my toolbag just for the hell of it. Having taken care of today's issues, I spent some time with the maintenance mechanic talking about their three-phase issues. It turns out (as it usually does) to be more complicated than originally stated:

There are about a dozen different machines that plug into a dozen or so outlets, in various combinations. I tested four outlets and found two wired clockwise and two wired counterclockwise.

The plan is to go to all the department heads and compile a list of all the equipment that plugs into three-phase power. We will check each outlet and modify as necessary to get them all running clockwise. Then we'll modify the wiring in the machines as necessary to get them all to run correctly on clockwise power.

This will all end up being a couple of solid days of work, but when it's done, it will be done. Forever. Until someone changes something...

But it was good today to see that the little $20 meter gave good, believable readings.

On Tue, 19 Jan 2016 11:26:49 -0800 (PST)
rangerssuck wrote:

snip
So, I was at the factory today to fix something completely
unrelated, but I threw the phase detector in my toolbag
just for the hell of it. Having taken care of today's
issues, I spent some time with the maintenance mechanic
talking about their three-phase issues. It turns out (as
it usually does) to be more complicated than originally
stated:

snip
But it was good today to see that the little $20 meter
gave good, believable readings.

Good to hear. After reading a few reviews for some of the less
expensive testers via Amazon people were having trouble with them.
Or they didn't know how to use them. One can never be sure ;-)

Thanks for the followup!

With the current prices, functions/abilities they have, I would get one
if I was still doing that kind of work.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Tuesday, January 19, 2016 at 3:27:51 PM UTC-5, Leon Fisk wrote:
On Tue, 19 Jan 2016 11:26:49 -0800 (PST)
rangerssuck wrote:

snip
So, I was at the factory today to fix something completely
unrelated, but I threw the phase detector in my toolbag
just for the hell of it. Having taken care of today's
issues, I spent some time with the maintenance mechanic
talking about their three-phase issues. It turns out (as
it usually does) to be more complicated than originally
stated:

snip
But it was good today to see that the little $20 meter
gave good, believable readings.

Good to hear. After reading a few reviews for some of the less
expensive testers via Amazon people were having trouble with them.
Or they didn't know how to use them. One can never be sure ;-)

Thanks for the followup!

With the current prices, functions/abilities they have, I would get one
if I was still doing that kind of work.

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

Yeah, it's nothing special, but the instructions are in Cinglish, so I can see how people would get confused.

The unit has five LEDs - L1, L2, L3, CW, CCW. It also has three test leads with screw-on alligator clips. All I did was connect the three leads to the appropriate terminals on a mating plug. If you get all three L LEDs, you have all the phases. One of the CW or CCW will light, telling you which direction you're wired.

There's also an anemic buzzer in there, that pulses for CW and is steady for CCW, but I could barely hear it in any of the four rooms I tested in.

There are better, more expensive testers, but this will certainly do what I need for this job.

I mentioned all this to my brother who is an electronics tech at a large USPS facility. He told me about the time they lost a phase and had to replace a LOT of contactor contacts and other stuff. A lot of noise and smoke.

He also said that even though they are meticulous about making sure that everything is wired correctly, and there's paperwork to prove it, they still have an only slightly better than 50/50 chance of being wrong when they install a new machine.

On Wed, 20 Jan 2016 10:45:20 -0800 (PST)
rangerssuck wrote:

snip
I mentioned all this to my brother who is an electronics
tech at a large USPS facility. He told me about the time
they lost a phase and had to replace a LOT of contactor
contacts and other stuff. A lot of noise and smoke.

I got to replace something like a 5hp 3-phase motor for an
air compressor once at the County Road Commission. They lost a phase and
the compressor tried to run on the remaining two. Rather than pull the
disconnect for it the guys in the shop just watched it kill itself over
a period of time...

Really hard place for an outside tech to work. End up with a bloody
tongue before long...

--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email