I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Then I can think about what to do with this.

i

On 10/27/2010 10:25 AM, Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Then I can think about what to do with this.

Definitely check or establish continuity between the VFD and lathe frame
to the ground wire. It should be there already, though.

Depending on how old the house is and who did the work, someone may have
cheated somewhere along the line and connected ground to neutral. This
is not uncommon in old two-wire systems that have been wired by someone
who knows the inspectors will check with a tester without looking
further (Lookie -- the green lights go on!). Depending on how the rest
of the house is wired and running you can have some significant voltage
on neutral, leading to mild shocks.

In large industrial installations its not uncommon to have different
grounds in different sections of a building be tens of volts different
-- I had a problem with this in a former workplace, where two such
sections came together in one part of the factory floor; plugging
diagnostic computers into one section and the system to be diagnosed in
the other lead to the magic smoke coming out. I can't imagine that
happening in a normal residential setting, though.

If you can figure out a way to check the potential between the ground
pin and the floor it may be educational, although I'm not sure what you
could do with it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Oct 27, 1:37*pm, Tim Wescott wrote:
On 10/27/2010 10:25 AM, Ignoramus15569 wrote:



I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Then I can think about what to do with this.

Definitely check or establish continuity between the VFD and lathe frame
to the ground wire. *It should be there already, though.

Depending on how old the house is and who did the work, someone may have
cheated somewhere along the line and connected ground to neutral. *This
is not uncommon in old two-wire systems that have been wired by someone
who knows the inspectors will check with a tester without looking
further (Lookie -- the green lights go on!). *Depending on how the rest
of the house is wired and running you can have some significant voltage
on neutral, leading to mild shocks.

In large industrial installations its not uncommon to have different
grounds in different sections of a building be tens of volts different
-- I had a problem with this in a former workplace, where two such
sections came together in one part of the factory floor; plugging
diagnostic computers into one section and the system to be diagnosed in
the other lead to the magic smoke coming out. *I can't imagine that
happening in a normal residential setting, though.

If you can figure out a way to check the potential between the ground
pin and the floor it may be educational, although I'm not sure what you
could do with it.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details athttp://www.wescottdesign.com/actfes/actfes.html

Had a house in MD, garage on one side of a stream house on the other
side.

"Ground" for the house was about 80 volts different from "Ground" at
the garage.

Dave

Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

i

On 10/27/2010 01:45 PM, Ignoramus15569 wrote:
Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

Well, whatever's causing the problem is the primary issue.

Do you only get zapped with the lathe turning?

With the VFD on no matter what?

Any time at all?

The further you get down that list and still say 'yes' the less likely
it is a motor problem, and the more likely it's a really odd ground problem.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 2010-10-27, Tim Wescott wrote:
On 10/27/2010 01:45 PM, Ignoramus15569 wrote:
Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

Well, whatever's causing the problem is the primary issue.

Do you only get zapped with the lathe turning?

Yes.

With the VFD on no matter what?

No

Any time at all?

Only when the motor is running.

The further you get down that list and still say 'yes' the less likely
it is a motor problem, and the more likely it's a really odd ground problem.

On Oct 27, 4:45*pm, Ignoramus15569 ignoramus15...@NOSPAM.
15569.invalid wrote:
Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

i

I'd suspect bypass cap current into neutral also. Can you run the VFD
with the motor disconnected to check?

jsw

On 10/27/2010 03:45 PM, Ignoramus15569 wrote:
Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

i

No. All motors "leak" as they have a lot of wire in close proximity to
the frame. The VFD makes this much worse, as instead of 60 HZ on the
windings, you have extremely fast sharp-edged PWM pulses at 400 V. The
wire to frame effectively creates a capacitor, and the faster the dv/dt,
the more current flows through the capacitor.

If you only got zapped when the motor was running, then the ground of
the lathe has to be open. If you got zapped ANY time you touched it,
then it sounds like the house ground might be going out.

Jon

"Ignoramus15569" wrote in message
...

Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

i


Make sure that ground and neutral at the plug are the same. Years ago had a
problem with a disk drive failing to spin up properly, and they had left off
the jumper at the pole between ground and neutral. Was 12 V between.

On Oct 27, 9:24*pm, "Califbill" wrote:

Make sure that ground and neutral at the plug are the same. *Years ago had a
problem with a disk drive failing to spin up properly, and they had left off
the jumper at the pole between ground and neutral. *Was 12 V between.

A minor addition to all the discussion about Iggy's ground problem.

When we lived in Washington state, about 12 years ago, the basement of
the house was finished with a suspended ceiling. It was very tight to
the floor joists above, so the panels were a bear to remove.

The electrical code, in WA, required two heavy wires to go from the
breaker panel to ground. They used the water pipes, as they were
soldered copper pipes all the way to where the line entered the house,
then 100+ feet to the meter.

Sure enough, there were two heavy wires going from the panel up into
the ceiling. And there were two heavy copper wires going from the
nearest cold water pipe, about 40 feet away in another room, going up
into the ceiling.

For some reason, I had to remove one of the ceiling panels and
discovered there was only a single copper ground wire up there. Some
smart electrician had tricked an inspector into believing both wires
were installed properly!

I just put the panel back in place.

Paul

On Thu, 28 Oct 2010 09:08:15 -0700 (PDT), KD7HB
wrote:

On Oct 27, 9:24*pm, "Califbill" wrote:

Make sure that ground and neutral at the plug are the same. *Years ago had a
problem with a disk drive failing to spin up properly, and they had left off
the jumper at the pole between ground and neutral. *Was 12 V between.

A minor addition to all the discussion about Iggy's ground problem.

When we lived in Washington state, about 12 years ago, the basement of
the house was finished with a suspended ceiling. It was very tight to
the floor joists above, so the panels were a bear to remove.

The electrical code, in WA, required two heavy wires to go from the
breaker panel to ground. They used the water pipes, as they were
soldered copper pipes all the way to where the line entered the house,
then 100+ feet to the meter.

Sure enough, there were two heavy wires going from the panel up into
the ceiling. And there were two heavy copper wires going from the
nearest cold water pipe, about 40 feet away in another room, going up
into the ceiling.

For some reason, I had to remove one of the ceiling panels and
discovered there was only a single copper ground wire up there. Some
smart electrician had tricked an inspector into believing both wires
were installed properly!

I just put the panel back in place.

Paul
I found one when I helped a friend move into a rented house. The panel
was at the front of the house and had a 3#8 stove cable going into the
wall. The kitchen at the back of the house had an identical 3#8 cable
coming out of the wall to connect to the stove. When I hooked up the
stove and re-inserted the fuse carrier, one of the fuses popped. The
replacement fuse cured the problem but we soon noticed an odd smell.
Turns out, the replacement fuse was higher rated and further
investigation revealed that when the kitchen had been moved to the
back of the house, the stove cable had been extended with 3#14 cable
and cross wired so that line 1 was connected to the neutral. There was
enough current to blow the 40 A fuse but not the 60A which heated the
#14 wire running through the attic
Gerry :-)}
London, Canada

Bill & All,
Never connect safety ground and neutral anywhere but the building entry point. It is unsafe, against code everywhere and it
creates ground loops. Safety ground must be non-current carrying. If you find this practice corrects a fault, you have another
problem find that and stick to code.
Steve

"Califbill" wrote in message m...
"Ignoramus15569" wrote in message ...

Tim, I will reply to other fine points that you made when I gather
more data, but yes, we had a very long dry spell with a very minor
rain a couple of days ago.

I will check, very meticulously, whether I have a continuous ground,
first.

Ultimately, though, the question is, is that the motor that is
leaking, and if so, isn't that the primary issue?

i


Make sure that ground and neutral at the plug are the same. Years ago had a problem with a disk drive failing to spin up
properly, and they had left off the jumper at the pole between ground and neutral. Was 12 V between.

I have looked at everything very carefully and found a place where
ground was not connected properly. Thanks to all. This lathe runs
very well now, everything pertaining to variable speed works extremely
well, VFD is working, etc. It cost me more to fix than I hoped (VS
stuff), but the result is very nice. The last thing remaining is to
make stops for the taper attachment.

i

On 10/27/2010 08:29 PM, Ignoramus15569 wrote:
I have looked at everything very carefully and found a place where
ground was not connected properly. Thanks to all. This lathe runs
very well now, everything pertaining to variable speed works extremely
well, VFD is working, etc. It cost me more to fix than I hoped (VS
stuff), but the result is very nice. The last thing remaining is to
make stops for the taper attachment.

Glad you found it -- it's really unpleasant when the electrical stuff
starts biting.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 2010-10-28, Tim Wescott wrote:
On 10/27/2010 08:29 PM, Ignoramus15569 wrote:
I have looked at everything very carefully and found a place where
ground was not connected properly. Thanks to all. This lathe runs
very well now, everything pertaining to variable speed works extremely
well, VFD is working, etc. It cost me more to fix than I hoped (VS
stuff), but the result is very nice. The last thing remaining is to
make stops for the taper attachment.

Glad you found it -- it's really unpleasant when the electrical stuff
starts biting.


I agree. So now I have the best of all worlds, VFD for running from
single phase, and hydraulic variable speed drive for preserving
mechanical advantage.

i

On Wed, 27 Oct 2010 20:54:21 -0700, Tim Wescott
wrote:

On 10/27/2010 08:29 PM, Ignoramus15569 wrote:
I have looked at everything very carefully and found a place where
ground was not connected properly. Thanks to all. This lathe runs
very well now, everything pertaining to variable speed works extremely
well, VFD is working, etc. It cost me more to fix than I hoped (VS
stuff), but the result is very nice. The last thing remaining is to
make stops for the taper attachment.

Glad you found it -- it's really unpleasant when the electrical stuff
starts biting.

Indeed. I believe I mentioned working on a misbehaving Large
machine..and after laying on the concrete floor in a pool of
sweat..reached up and grabbed the side of the machine to pull myself up.

And having the shop owner kick my arm loose as I was doing the Spastic
Trout On The Dock dance......

Gunner


I am the Sword of my Family
and the Shield of my Nation.
If sent, I will crush everything you have built,
burn everything you love,
and kill every one of you.
(Hebrew quote)

On Sat, 30 Oct 2010 19:05:11 -0700, Gunner Asch
wrote:

On Wed, 27 Oct 2010 20:54:21 -0700, Tim Wescott
wrote:

On 10/27/2010 08:29 PM, Ignoramus15569 wrote:
I have looked at everything very carefully and found a place where
ground was not connected properly. Thanks to all. This lathe runs
very well now, everything pertaining to variable speed works extremely
well, VFD is working, etc. It cost me more to fix than I hoped (VS
stuff), but the result is very nice. The last thing remaining is to
make stops for the taper attachment.

Glad you found it -- it's really unpleasant when the electrical stuff
starts biting.

Indeed. I believe I mentioned working on a misbehaving Large
machine..and after laying on the concrete floor in a pool of
sweat..reached up and grabbed the side of the machine to pull myself up.

And having the shop owner kick my arm loose as I was doing the Spastic
Trout On The Dock dance......

That's NOT the approved Method of Faulty Ground Tracing as mentioned
in the Sparky manual, sir. But it found your problem for you, dinnit?
(ouch!)

--
Small opportunities are often the beginning of great enterprises.
-- Demosthenes

On Wed, 27 Oct 2010 12:25:22 -0500, Ignoramus15569
wrote:

I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Then I can think about what to do with this.

i

Just a data point for you. I just got my large mill power supply
running. I get 21 volts D.C. between neutral and ground. I attached a
ground rod to this main panel. I've never seen this large a value. If
I touched neutral while standing bare foot on steel, I'm sure it would
tickle.

Anyway, I'd suspect neutral is touching your frame someplace.

Karl

Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I'll bet you don't. I'd hook a long wire to a
water pipe and measure between it and the VFD.
If you're getting zapped, I'll bet there's at
least a 40 volt AC difference between the water
pipe and the VFD chassis.

Follow the ground wire back to the service entrance
measuring the voltage. See if it drops to zero
at some point. Be sure your multimeter is set
to AC volts.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

Pretty much. Florescent lights with old style magnetic
ballasts would do the same thing. The frame of the light
can float up from ground enough to give you a good tingle
if not grounded.

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

Try to find an open ground first.

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Good plan. Let us know what you find.

Then I can think about what to do with this.

i

"Jim Stewart" wrote...
Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

Good so far, but a separate ground wire from the lug to the lathe would be a
good idea.


I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I'll bet you don't. I'd hook a long wire to a
water pipe and measure between it and the VFD.
If you're getting zapped, I'll bet there's at
least a 40 volt AC difference between the water
pipe and the VFD chassis.

Follow the ground wire back to the service entrance
measuring the voltage. See if it drops to zero
at some point. Be sure your multimeter is set
to AC volts.

If you've had a long dry spell the ground resistance can increase a lot - I
sometimes have to water mine (as part of the 3-monthly check I do on my shed
electrics) to get a safe resistance...

If you want / need to measure it, get a low-voltage transformer and attach
one side of the low volts winding to the earth rod, other to a "roving"
earth rod that you hammer into the earth and water (or if the local elec.
co, provide one, use that) - do this in a number of spots at least 20-30
yards away and measure the AC voltage and the current into the rod, V/I will
give you the resistance, check your local electrical code for the minimum
value - to save the transformer for next time you may need a bulb in series
with the low volts if the earth is any good - DAMHIK

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

Pretty much. Florescent lights with old style magnetic
ballasts would do the same thing. The frame of the light
can float up from ground enough to give you a good tingle
if not grounded.

Dunno about VFDs (mine is on a *short, thick* cable to a pair of local earth
spikes), but when I play with the ham radio (which has high frequencies
buzzing about, although a few octaves above VFD frequencies) I find the
house earth is too long for satisfactory earthing and I have RF on the
equipment cases... for a narrow range of frequencies a 1/4 wavelength wire
(insulated at the far end) works to absorb it, being a dead short at the
right frequency - not easy to do for a *variable* frequency drive, tho! The
VFD output is a chopped square wave, so has some pretty high-frequency
components at fairly high voltages that can be a problem to shield
effectively and can't be filtered easily (the magic smoke leaks out of the
VFD if the HF impedance is too low) - one of the reasons that cable choice
is important when installing 'em.

My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?

Try to find an open ground first.

In any case, my plan for tonight is

1) Check that I do have a continuous ground path from home ground rod
to the VFD
2) Measure the voltage of that leakage
3) Add one more single conductor green cable, from the VFD ground lug,
bolted to the body of the lathe.

Good plan. Let us know what you find.

Then I can think about what to do with this.

i


High-resistance in the ground circuit would be my first thought, too

Dave H.
--
(The engineer formerly known as Homeless)

"Rules are for the obedience of fools, and the guidance of wise men" -
Douglas Bader

Jim Stewart wrote:

Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I'll bet you don't. I'd hook a long wire to a
water pipe and measure between it and the VFD.


Even metal water pipe can be a poor ground, and if you have much
current flowing it will damage the pipe at the joints.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Michael A. Terrell wrote:

Jim Stewart wrote:

Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I'll bet you don't. I'd hook a long wire to a
water pipe and measure between it and the VFD.


Even metal water pipe can be a poor ground, and if you have much
current flowing it will damage the pipe at the joints.

I didn't mean to imply that he should bond the VFD
to the water pipe. Just to use it as a ground
reference while he looks for an open in the house
and machine grounds.

Jim Stewart wrote:

Michael A. Terrell wrote:

Jim Stewart wrote:

Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I'll bet you don't. I'd hook a long wire to a
water pipe and measure between it and the VFD.


Even metal water pipe can be a poor ground, and if you have much
current flowing it will damage the pipe at the joints.

I didn't mean to imply that he should bond the VFD
to the water pipe. Just to use it as a ground
reference while he looks for an open in the house
and machine grounds.


If the joints are corroded, it isn't a good reference. It can get
you killed when you don't read enough voltage to bother you, when it is
much higher. Also, with a VFD there may be a lot of harmonics on the
neutral and running a wire to a water pipe won't show them.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On 10/27/2010 12:25 PM, Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

I am pretty sure, though I will triple check tonight, that I have a
continuous ground path to my home panel and to the buried ground rod
outside.

I always thought that there was no problem with the VFD/lathe etc, but
that is only because I always wore rubber soled shoes (crocs, boots
etc).

Yesterday I ran it without shoes and I was unpleasantly "zapped" when
I touched the VFD or the metal lathe itself.

So my question is WTF. Even if the motor "leaks" current due to
coltage spikes, shouldn't the grounding take care of it?

Your safety ground system, somewhere, has a problem. it COULD be the
ground for the lathe is bad, or it could be the entire ground for the
whole house is going out. this is quite common. Our ground went out
somev time ago, but fortunately, the whole feeder went out in the same
event, so we lucked out and didn't fry all the 120 V stuff in the house.
Our neighbor was not so fortunate, and a bunch of electronics got fried.

So, basically, trust NOTHING, assume NOTHING.
My second question is what would you suggest doing. Just giving up on
the VFD and using a phase converter, or try to replace the 3 HP motor?
Anyone knows if the motors on 6900 series lathes are 182 frame?
These are most likely NOT the problem. Turn the VFD and lathe on, and
then just keep working back to the panel. You need a real ground
reference, but as I said above, you can't trust anything. You may have
to drop a bar in the ground to get a real reference. But, you may be
able to hook an extension cord to a known-good outlet somewhere else in
the house, and then use the ground terminal on it with a meter to probe
around to find the open ground connection.

In many wood homes, you can have a totally screwed up ground system, and
have NO IDEA anything is wrong. But, if all your other machines are OK
(I would NOT go around testing them with the bare feet and wet finger
technique!) then it is just something on the lathe. If your safety
ground is tied THROUGH the VFD, that is a definite possible culprit
there. Could be a misunderstanding of what terminal is what, or just a
bad connection. And, just because you have one continuous "wire" from
here to there, don't be absolutely SURE there is solid copper all the
way. As I said, trust NOTHING!

Jon

On 10/27/2010 12:25 PM, Ignoramus15569 wrote:
I have a VFD, mounted on my Clausing 6913 lathe.

The VFD is mounted on an aluminum plate, which in turn is bolted to a
bracket, which is bolted to the lathe, with various metal parts and
metal screws.

The VFD has a ground lug, which I connected to the incoming cable.

Hmm, I didn't read this carefully before. Do NOT make safety ground
connections through anything aluminum and not expressly designed for
wire termination. Aluminum instantly builds an oxide layer, and that
can be quite a good insulator. Anodized aluminum can withstand several
thousand volts, and some anodized aluminum cannot be distinguished from
plain. But, anything bolted to aluminum sheet or whatever cannot be
trusted to carry a safety ground over time. Make a copper wire
connection for your safety ground, with terminal lugs approved for
electrical connections.

I'm just guessing here, but this could be it. It also could be that
your VFD case is isolated from the inner safety ground frame, so you
grounded the VFD, but not the plate.

Jon

Further to this discussion, and not in response to any particular
post, Plumbers are not great fans of cold water pipes being used as
electrical grounds. And for good reason. If there is a ground fault,
and the pipe is carrying any current, and a plumber has to cut the
pipe to do a plumbing repair, that current tries to pass through the
plumber.

Also, any plastic pipe in the system obviously has to be bypassed with
wire, though it ususlly isn't, resulting in bad (no) grounds
downstream of the plastic.

IMO, if you are going to use the cold water pipe as your ground
connection, you really ought to do it right at the point where it
enters the building, before any plumbing connections (which could
corrode and develop high resistance.

I'm getting ready to replace my service entrance, and there will be
multiple ground rods.

--

On another note, if you dond find an actual mising or broken ground
wire, and the conclusion is that the potential difference is due to
earth resistance between the ground rod and the slab near the lathe, a
conductive mat on the floor bonded to the frame of the lathe may not
be a bad idea.

On Thu, 28 Oct 2010 09:44:08 -0700 (PDT), rangerssuck
wrote:

Further to this discussion, and not in response to any particular
post, Plumbers are not great fans of cold water pipes being used as
electrical grounds. And for good reason. If there is a ground fault,
and the pipe is carrying any current, and a plumber has to cut the
pipe to do a plumbing repair, that current tries to pass through the
plumber.

Also, any plastic pipe in the system obviously has to be bypassed with
wire, though it ususlly isn't, resulting in bad (no) grounds
downstream of the plastic.

IMO, if you are going to use the cold water pipe as your ground
connection, you really ought to do it right at the point where it
enters the building, before any plumbing connections (which could
corrode and develop high resistance.

I'm getting ready to replace my service entrance, and there will be
multiple ground rods.
When I re-wired my previous house, I moved the service panel to
directly below the kitchen. Since I had a good supply of salvaged,
bare, #6 stranded wire, I ran that from the incoming water line
through the service ground lug the and further on to connect both hot
and cold feeds and the copper drain at the kitchen sink. The inspector
thought that the drain line grounding was such a good idea, I gave him
an extra ground clamp and enough wire to modify his own home system.

He told me the story of the guy that wired his rec. room much more
cheaply than anyone else. Investigation revealed that all his wire was
300 ohm twin lead.
Gerry :-)}
London, Canada

"Gerald Miller" wrote...
When I re-wired my previous house, I moved the service panel to
directly below the kitchen. Since I had a good supply of salvaged,
bare, #6 stranded wire, I ran that from the incoming water line
through the service ground lug the and further on to connect both hot
and cold feeds and the copper drain at the kitchen sink. The inspector
thought that the drain line grounding was such a good idea, I gave him
an extra ground clamp and enough wire to modify his own home system.


Here in the UK that's compulsory, known as "supplemental bonding" of
basically all metalwork that could be touched in "special locations", i.e.
kitchens, bathrooms... Some "electricians" go to town and have ugly cables
appearing from floors to bond the central heating radiators and handrails
too, rather than make an effort and lift a floorboard We're not allowed
to use the water supply pipe as a protective earth (ground) though, as a lot
of homes now have plastic incoming pipework!

Is electrical work as tightly regulated in the US as it is here? We've had
new laws ("statutory instruments" that don't go before a vote in Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond replacing
an existing switch, light fitting, socket or piece of damaged cable etc.
(and not even that in the bathroom and kitchen!), the local council building
control office have to be informed and handed inspection certificates
(produced by members of an "approved scheme" who often refuse to certify
anyone else's work or charge almost as much as having them do the work from
start to finish) etc. - of course, this has resulted in "old colours" cables
selling at a premium as the new laws came in after a change of cable core
colours and another result is that more and more people are tripping over
overloaded extension cables...
The law (Part P of the Building Regulations) was put in force after a
politician's son-in-law screwed a metal shelf in through a cable in the wall
without checking for cables first, and his wife died from touching that and
her dishwasher, so it got blamed on the contractor - no avoiding stupidity I
guess, however hard Nanny tries to legislate, the only law you can really
count on is Darwin's...

He told me the story of the guy that wired his rec. room much more
cheaply than anyone else. Investigation revealed that all his wire was
300 ohm twin lead.

Friends of mine bought a falling-down farmhouse in La Belle France a few
years ago, and discovered the wiring was mostly bell-wire (that you'd use to
connect a doorbell button) - nice when they plugged in a 3KW heater and
wondered what the burning smell was! A rewire was one of the first steps in
the rebuild, and done to the same standard they've applied to the rest of
the building - damn near perfect

Dave H.
--
(The engineer formerly known as Homeless)

"Rules are for the obedience of fools, and the guidance of wise men" -
Douglas Bader

On 2010-10-29, Dave H. wrote:
Is electrical work as tightly regulated in the US as it is here? We've had
new laws ("statutory instruments" that don't go before a vote in Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond replacing
an existing switch, light fitting, socket or piece of damaged cable etc.
(and not even that in the bathroom and kitchen!), the local council building
control office have to be informed and handed inspection certificates

You have quite insane gun control too, now people cannot own guns and
cannot install receptacles, pretty weird country I would say.

i

You might feel it's an unneccessary issue, Ig... so you apparently believe
you should have that freedom (assuming that you believe you're intelligent
enough to do work like this),

...and yet, your lathe has probably had a ground fault for all this time.

An earth ground is a single conductor.. how hard can it be?

When wiring anything that's line powered.. a replacement receptacle or a
major piece of equipment, the first connection I make is to a known good
earth ground.
The earth ground doesn't get disconnected until the equipment is taken out
of service, with all power conductors removed (bare ends cut off or capped
with wire nuts).

Everyone doing any electrical work should know how little electrical current
it takes to disrupt normal heart rhythm.
This info is included in NEC manuals and numerous other sources.

--
WB
..........


"Ignoramus1553" wrote in message
...
On 2010-10-29, Dave H.
wrote:
Is electrical work as tightly regulated in the US as it is here? We've
had
new laws ("statutory instruments" that don't go before a vote in
Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond
replacing
an existing switch, light fitting, socket or piece of damaged cable etc.
(and not even that in the bathroom and kitchen!), the local council
building
control office have to be informed and handed inspection certificates

You have quite insane gun control too, now people cannot own guns and
cannot install receptacles, pretty weird country I would say.

i

On Oct 29, 8:50*am, Ignoramus1553
wrote:
On 2010-10-29, Dave H. wrote:

*Is electrical work as tightly regulated in the US as it is here? We've had
new laws ("statutory instruments" that don't go before a vote in Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond replacing
an existing switch, light fitting, socket or piece of damaged cable etc..
(and not even that in the bathroom and kitchen!), the local council building
control office have to be informed and handed inspection certificates

You have quite insane gun control too, now people cannot own guns and
cannot install receptacles, pretty weird country I would say.

i

http://www.moonbattery.com/archives/...in_starts.html

Dave H. wrote:
"Gerald Miller" wrote...
When I re-wired my previous house, I moved the service panel to
directly below the kitchen. Since I had a good supply of salvaged,
bare, #6 stranded wire, I ran that from the incoming water line
through the service ground lug the and further on to connect both hot
and cold feeds and the copper drain at the kitchen sink. The inspector
thought that the drain line grounding was such a good idea, I gave him
an extra ground clamp and enough wire to modify his own home system.


Here in the UK that's compulsory, known as "supplemental bonding" of
basically all metalwork that could be touched in "special locations", i.e.
kitchens, bathrooms... Some "electricians" go to town and have ugly cables
appearing from floors to bond the central heating radiators and handrails
too, rather than make an effort and lift a floorboard We're not allowed
to use the water supply pipe as a protective earth (ground) though, as a lot
of homes now have plastic incoming pipework!

Is electrical work as tightly regulated in the US as it is here? We've had
new laws ("statutory instruments" that don't go before a vote in Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond replacing
an existing switch, light fitting, socket or piece of damaged cable etc.
(and not even that in the bathroom and kitchen!), the local council building
control office have to be informed and handed inspection certificates
(produced by members of an "approved scheme" who often refuse to certify
anyone else's work or charge almost as much as having them do the work from
start to finish) etc. - of course, this has resulted in "old colours" cables
selling at a premium as the new laws came in after a change of cable core
colours and another result is that more and more people are tripping over
overloaded extension cables...

In most places in the US, local laws set the
specific requirements and usually compliance
with the National Electrical Code is one of them.

My first home was in a city that forbid anyone but
a non-licensed electrician from doing andy electrical
work. Where I live now, a homeowner can do any
electrical work providing he can submit a building
permit request, get it approved, and pass an
inspection by the city building inspector.

I installed a 50 ampere subpanel along with lights
and 220 outlets for lathe, mill and welder and had
no problem with either the permit or the inspection.

About 25 years ago I designed several test fixtures
for the computer company I worked for and sent two
of them to our plant in Woking/Bracknell. I visited
the plant a few months later and was surprised at the
extensive plexi/perspex covers they installed over it.

Jim Stewart wrote:


In most places in the US, local laws set the
specific requirements and usually compliance
with the National Electrical Code is one of them.

My first home was in a city that forbid anyone but
a non-licensed electrician from doing andy electrical
^^^^^^^^^^^^^^^^^^^^^^^^

work. Where I live now, a homeowner can do any
electrical work providing he can submit a building
permit request, get it approved, and pass an
inspection by the city building inspector.

I installed a 50 ampere subpanel along with lights
and 220 outlets for lathe, mill and welder and had
no problem with either the permit or the inspection.

About 25 years ago I designed several test fixtures
for the computer company I worked for and sent two
of them to our plant in Woking/Bracknell. I visited
the plant a few months later and was surprised at the
extensive plexi/perspex covers they installed over it.


--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

On Fri, 29 Oct 2010 13:07:09 +0100, "Dave H."
wrote:


"Gerald Miller" wrote...
When I re-wired my previous house, I moved the service panel to
directly below the kitchen. Since I had a good supply of salvaged,
bare, #6 stranded wire, I ran that from the incoming water line
through the service ground lug the and further on to connect both hot
and cold feeds and the copper drain at the kitchen sink. The inspector
thought that the drain line grounding was such a good idea, I gave him
an extra ground clamp and enough wire to modify his own home system.


Here in the UK that's compulsory, known as "supplemental bonding" of
basically all metalwork that could be touched in "special locations", i.e.
kitchens, bathrooms... Some "electricians" go to town and have ugly cables
appearing from floors to bond the central heating radiators and handrails
too, rather than make an effort and lift a floorboard We're not allowed
to use the water supply pipe as a protective earth (ground) though, as a lot
of homes now have plastic incoming pipework!

Don't some still use the old wooden water supply pipes?

Is electrical work as tightly regulated in the US as it is here? We've had
new laws ("statutory instruments" that don't go before a vote in Parliament)
inflicted on us that pretty much outlaw DIY electrical work beyond replacing
an existing switch, light fitting, socket or piece of damaged cable etc.
(and not even that in the bathroom and kitchen!), the local council building
control office have to be informed and handed inspection certificates
(produced by members of an "approved scheme" who often refuse to certify
anyone else's work or charge almost as much as having them do the work from
start to finish) etc. - of course, this has resulted in "old colours" cables
selling at a premium as the new laws came in after a change of cable core
colours and another result is that more and more people are tripping over
overloaded extension cables...

Union influence? - I refused to even consider going on a holiday to
help senior son renovate his 100+ year old house in Walthamstow ~2002
The law (Part P of the Building Regulations) was put in force after a
politician's son-in-law screwed a metal shelf in through a cable in the wall
without checking for cables first, and his wife died from touching that and
her dishwasher, so it got blamed on the contractor - no avoiding stupidity I
guess, however hard Nanny tries to legislate, the only law you can really
count on is Darwin's...

He told me the story of the guy that wired his rec. room much more
cheaply than anyone else. Investigation revealed that all his wire was
300 ohm twin lead.

Friends of mine bought a falling-down farmhouse in La Belle France a few
years ago, and discovered the wiring was mostly bell-wire (that you'd use to
connect a doorbell button) - nice when they plugged in a 3KW heater and
wondered what the burning smell was! A rewire was one of the first steps in
the rebuild, and done to the same standard they've applied to the rest of
the building - damn near perfect

Dave H.
Gerry :-)}
London, Canada