I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Ignoramus20688 wrote:


My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.


IIRC, step up / step down transformers do have a few tricks to make them more efficient
going one direction. I belive there was some mention of eddy currents and such because
one winding was next to the core and the other farther away or something like that.

This was a recent subject of discussion.

I doubt it is more than 10% going the wrong way. Monitor the temperature of the
transformer, for your intermittant duty plasma cutter, I'd not be too worried if the
numbers work out.

Btw, I've seen 440, 460, 480. Looks like 10% variation isn't a big deal.

As far as starting the motor, I bet it works. We use a lot of transformers to step down
480v to 240v to run cnc equipment. I don't think we are padding the KVA requirement too
much.

Fuse the thing and give it a whirl.

Wes

"Ignoramus20688" wrote in message
...
I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.
--
Due to extreme spam originating from Google Groups, and their
inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/
I think it will work fine and you should be able to draw 10 KVA if you have
adequate primary power. I don't think 10 KVA is going to do much for a 1500
ampere welder but it might give it a functional test at least.

Be very careful as you are dealing with not only a lethal voltage but also
enough power to make things exciting if something goes wrong.

Don Young

Ignoramus20688 wrote:


It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.

Hi Iggy;

Buck boosts run fine either way, "Buck only" won't. Look for a "270 or
277" voltage among the outputs. If it's there, there is a good chance
that the high voltage winding has a tap for 277 common with the
enclosure and introducing power through the low volt windings will cause
a dead short.

If it does have a 277 tap you'll need to cut the internal wires that
attach to the case (sometimes as many as 4) and ground only on the input
or just run it ungrounded (lots of folks do).

Matt

As you are about to venture into the area of high voltage equipment, if you
don't have previous experience in this area, you should be prepared and
equipped with the proper supplies and equipment.

It would be a good time to contemplate your earlier concern related to those
high voltage capacitors you had at one time.

You should be prepared by going to an electrical supply (not a consumer
store hardware department) for properly rated wire and all termination
parts.. this includes properly rated switches and fuses too.

A transformer like the one referred to won't shut itself off just because
there happens to be a piece of meat between/across the terminals.

Ordinary household wire isn't suitable or safe for use at higher voltages.
Jackets on romex-type jackets are marked with a 600V rating, but that only
applies as the design/manufacturing specifications rating when the wire is
used properly up into the 200+VAC range (not bent, twisted in a knot,
tightly kinked or otherwise abused).

A nick in the insulation of a conductor carrying 400+VAC is very likely to
cause an arc-over if it gets near another conductor or grounded metal part.
This hazardous event might not be so spectacular, but someone may react by
flinching/jumping/falling onto or into an object that could cause injury.
An observer looking under the hood of a car, someone blows the horn, the
observer reacts and bumps head on car hood, sort of scenario.

I'm fairly certain that no one would like to experience a surprise corona
taking place in their home or shop.

It would be very wise to not trust the integrity of a cheap DMM or other
test/measurement equipment on high votage equipment.
High voltages require properly designed test instruments in good operating
condition (not de-rated by by improvised repairs).
The user needs to understand and respect the capabilities of the test
equipment designed for high voltages. Designed for the purpose, not made in
an alley with a lot of inferior components, made to look like a real
instrument.

I've personally seen poor quality meters that have had internal flash-overs
when used on high voltages. I could easily see the outline of the users'
fingers on the meter cases and probes.

I don't know what might be more hazardous than having a corona take place in
one hand with the other hand holding a probe on a high voltage terminal
inside a cabinet full of high voltage connections, with the exceptions of
playing with guns or explosives.

Current passing thru the heart is often deadly.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Ignoramus20688" wrote in message
...
I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.
--
Due to extreme spam originating from Google Groups, and their
inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

"Ignoramus20688" wrote in message
...
I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.


It may make 460 volts, but unless its a 3 phase transformer with 3 phases
in and out, the motor likely won't work.
Most motors of that size are 3 phase and simply buzz, overhat and burn out
when fed single phase.

On 2008-11-23, Grumpy wrote:

"Ignoramus20688" wrote in message
...
I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.


It may make 460 volts, but unless its a 3 phase transformer with 3 phases
in and out, the motor likely won't work.
Most motors of that size are 3 phase and simply buzz, overhat and burn out
when fed single phase.



Grumpy, I was thinking of setting it up as a phase converter.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Wild Bill, all good points, especially about special wire on the 480v
side. I will only use wire rated at 600v AC.

i

Most electrical equipment is good for plus or minus 10% minimum. Therefore your 460v
equipment should work just fine on 440v or 480v.

Ignoramus20688 wrote:
I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.

In article ,
Ignoramus20688 wrote:

I have a plasma cutter that is slightly broken (Hypertherm 600 with
cracked torch-to-machine plug). The plasma cutter is 460 v only. (no
kidding). So it sat in my shed for a few years as I had no 460v.

I also have a Lincoln Idealarc DC-1500 welder which I need to test.
(1,500 amp, 1,800 lbs monster). (I want to be clear that whether I can
at all get any life out of it with a 10 kVa single phase transformer,
is not obvious)

This is the prelude.

The story is that one of the mystery devices that I brought turns out
to be what I long wanted to get, which is a 10 kVa ACME Transformer.

It is a multitap thing that allows buck/boost adjustments of a few
percent. It has various taps that I could use if, say, I have 490
volts input and want 240v output. It is nicely laid out inside a
hexagonal transformer box, whose windings are sealed with epoxy.

My first question is, am I correct in assuming that I could use it in
reverse to get 460v from 240, at some reduced kVa. Also, what is the
realistic kVa number I could get from it.

Transformers do work in revers just fine.


So, my thinking goes, to make it into a 240-460 transformer, I should
allow for some losses and wire it according to the diagram connection
for 480 volts. Then under load, and due to losses, the voltage would
drop a little to 460. Right?

Probably, but don't miswire it. I would be generous with the fuses, and
do the initial tryout using a variac to drive the 240-volt input,
creeping up and measuring voltages to see that things are following the
script before applying full power.

At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.


The bonus question is whether this thing could power a 10 HP motor to
make three phase 460v.

It's possible, if you can get past the startup surge. A pony motor may
be needed to spin the big guy up, to reduce the surge.

You can also use a 480-volt VFD to make the three phase from
single-phase 480 volt power.

Joe Gwinn

"Wild_Bill" wrote:

As you are about to venture into the area of high voltage equipment,
Technically not high voltage. But high voltage relative to what you
are probably used to.


You should be prepared by going to an electrical supply (not a consumer
store hardware department) for properly rated wire and all termination
parts.. this includes properly rated switches and fuses too.
WHile this is correct, your corner hardware store will probably have
properly rated "termination parts " and wire. May or may not have
properly rated switches, fuses and breakers


Ordinary household wire isn't suitable or safe for use at higher voltages.
Jackets on romex-type jackets are marked with a 600V rating, but that only
applies as the design/manufacturing specifications rating when the wire is
used properly up into the 200+VAC range (not bent, twisted in a knot,
tightly kinked or otherwise abused).

Untrue. If the wire is marked with 600V rating, then it is suitable
for use at all voltage up to 600V, period. Using it "bent, twisted in
a knot, tightly kinked or otherwise abused" at 120V and you still have
a problem. [And only the last two of those are really a problem
anyway]



A nick in the insulation of a conductor carrying 400+VAC is very likely to
cause an arc-over if it gets near another conductor or grounded metal part.
Not significantly more so that 120/208 or 240,, slightly more so yes.
Given the lashup he is contemplating, the same nick at 240 is likely
to be significantly more spectacular when it goes up, due to the much
larger available fault current.
taking place in their home or shop.

It would be very wise to not trust the integrity of a cheap DMM or other
test/measurement equipment on high votage equipment.

MANY of the cheap ones are rated 300V only.

High voltages require properly designed test instruments in good operating
condition (not de-rated by by improvised repairs).
Damn straight

I've personally seen poor quality meters that have had internal flash-overs
when used on high voltages. I could easily see the outline of the users'
fingers on the meter cases and probes.
That (finger outline) is unlikely for an internal flash over itself.
THat takes an external flash over, usually generated when the user
pulls the test leads away from the voltage source, while the internal
arc still exists.


I don't know what might be more hazardous than having a corona take place in

one hand with the other hand holding a probe on a high voltage terminal
inside a cabinet full of high voltage connections, with the exceptions of
playing with guns or explosives.

I do! It is generating an arc under those same conditions. Even more
dangerous is doing that without the proper PPE.

[Corona is a different animal entirely, and is almost nonexistent at
600V and below. It is even unusual at 4160. Common however at 7200
and up. And the more UP you get the more common it becomes.]


jk

On Sun, 23 Nov 2008 12:33:03 -0500, Joseph Gwinn
wrote:

In article ,
Ignoramus20688 wrote:


So, my thinking goes, to make it into a 240-460 transformer,

At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

There's no prohibition on manually operated switches up to at least
600VAC that I'm aware of, as long as the switch is properly rated.
600V switches are widely available.

--
Ned Simmons

On 2008-11-23, Ned Simmons wrote:
On Sun, 23 Nov 2008 12:33:03 -0500, Joseph Gwinn
wrote:

In article ,
Ignoramus20688 wrote:


So, my thinking goes, to make it into a 240-460 transformer,

At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

There's no prohibition on manually operated switches up to at least
600VAC that I'm aware of, as long as the switch is properly rated.
600V switches are widely available.


I wanted to use switches on the 240v input side.
--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

Joseph Gwinn wrote:


At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.

They do get BIG as the voltage gets higher, Size of a hallway closet
in the case of 12 and 21 KV.
jk

On Nov 24, 6:42*pm, jk wrote:
Joseph Gwinn wrote:

At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. *I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.

They do get BIG as the voltage gets higher, Size of a hallway closet
in the case of 12 and 21 KV.
jk

And do not stand in front of the switch when you turn it off. If it is
running full load to a reactive device, the arc may blow the cover
open.

Paul

In article ,
jk wrote:

Joseph Gwinn wrote:


At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.

They do get BIG as the voltage gets higher, Size of a hallway closet
in the case of 12 and 21 KV.
jk

I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

Joe Gwinn

On Tue, 25 Nov 2008 20:31:18 -0500, Joseph Gwinn
wrote:

In article ,
jk wrote:

Joseph Gwinn wrote:


At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.

They do get BIG as the voltage gets higher, Size of a hallway closet
in the case of 12 and 21 KV.
jk

I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

Perhaps he was talking about some requirement other than the NEC. For
example, I built equipment for GE's steam turbine division and they
had some in-house rules that were considerably stricter than the NEC.
The one that comes to mind was a limit of 240V in flexible cords.


Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

I've seen it happen on a 480V motor starter. Pretty exciting.

--
Ned Simmons

Joseph Gwinn wrote:

At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.
k

I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

There is no difference form the code point of view.
A switch is acceptable for use at all voltages up to it's rated
voltage.

Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

2 Issues here,
1 is if it does that it is being used on a circuit where the
available fault is greater than it is rated for. [ the kAIC rating]
And 2: Contactors fail that way too and much more frequently.

[Because they see a much larger number of operations]

jim

jk

In article ,
Ned Simmons wrote:

On Tue, 25 Nov 2008 20:31:18 -0500, Joseph Gwinn
wrote:

In article ,
jk wrote:

Joseph Gwinn wrote:


At that voltage level, you are not allowed to use directly activated
switches, and must instead use contactors in grounded metal boxes, and
so on. I'm sure we will hear from the electricians on the group about
that.

Completely not the case.

You can use switches up to any level, yes,direct manually actuated
ones.

They do get BIG as the voltage gets higher, Size of a hallway closet
in the case of 12 and 21 KV.
jk

I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

Perhaps he was talking about some requirement other than the NEC. For
example, I built equipment for GE's steam turbine division and they
had some in-house rules that were considerably stricter than the NEC.
The one that comes to mind was a limit of 240V in flexible cords.

The electrician probably had local industrial practice and/or code in
mind. He was very definite on the subject, but didn't mention where the
rule came from. The conversation was in an old mill building in
Pawtucket, RI, that houses a number of small manufacturers.


Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

I've seen it happen on a 480V motor starter. Pretty exciting.

Hope the cover was screwed down tightly.

This may be the reason for such a local rule.

I've read that there is a big difference between 240 volts and 480 volts
- with the lower voltage, arcs over common insulators will usually
self-extinguish, while at 480 they will not extinguish until power is
removed.

Joe Gwinn

On Thu, 27 Nov 2008 22:18:30 -0500, Joseph Gwinn
wrote:

In article ,
Ned Simmons wrote:

On Tue, 25 Nov 2008 20:31:18 -0500, Joseph Gwinn
wrote:


I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

Perhaps he was talking about some requirement other than the NEC. For
example, I built equipment for GE's steam turbine division and they
had some in-house rules that were considerably stricter than the NEC.
The one that comes to mind was a limit of 240V in flexible cords.

The electrician probably had local industrial practice and/or code in
mind. He was very definite on the subject, but didn't mention where the
rule came from. The conversation was in an old mill building in
Pawtucket, RI, that houses a number of small manufacturers.

In that environment they could have been following JIC/NFPA79
guidelines for machinery, which specify that control voltage should be
115VAC. The intent is that switches on control panels, limit switches,
contactor coils, etc., operate at 115V. This does not preclude higher
voltage at disconnects and manual power switches. These are voluntary
standards and are not intended to be applied to premises wiring. If I
have a choice, I use 24VDC controls on the equipment I build.



Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

I've seen it happen on a 480V motor starter. Pretty exciting.

Hope the cover was screwed down tightly.

It was before the bang, it was across the room after. g

--
Ned Simmons

In article ,
Ned Simmons wrote:

On Thu, 27 Nov 2008 22:18:30 -0500, Joseph Gwinn
wrote:

In article ,
Ned Simmons wrote:

On Tue, 25 Nov 2008 20:31:18 -0500, Joseph Gwinn
wrote:


I didn't qualify it enough. I'm not talking about substation switches.
I heard this from an electrician in Rhode Island.

Perhaps he was talking about some requirement other than the NEC. For
example, I built equipment for GE's steam turbine division and they
had some in-house rules that were considerably stricter than the NEC.
The one that comes to mind was a limit of 240V in flexible cords.

The electrician probably had local industrial practice and/or code in
mind. He was very definite on the subject, but didn't mention where the
rule came from. The conversation was in an old mill building in
Pawtucket, RI, that houses a number of small manufacturers.

In that environment they could have been following JIC/NFPA79
guidelines for machinery, which specify that control voltage should be
115VAC. The intent is that switches on control panels, limit switches,
contactor coils, etc., operate at 115V. This does not preclude higher
voltage at disconnects and manual power switches. These are voluntary
standards and are not intended to be applied to premises wiring. If I
have a choice, I use 24VDC controls on the equipment I build.

This sounds reasonable. As I recall, we were talking about a big
480-volt Clausing four-spindle gang drill press.


Another poster mentioned arcs blowing the cover off so one should stand
off to one side. Sounds like a job for a contactor in a steel box.

I've seen it happen on a 480V motor starter. Pretty exciting.

Hope the cover was screwed down tightly.

It was before the bang, it was across the room after. g

Sounds like a stronger box was needed. And/or bigger, to dilute the
overpressure. Until the main breaker pops.


Joe Gwinn