On Fri, 28 Dec 2007 13:27:12 -0800 (PST), willray
wrote:


Greetings -

Looking for some advice on running a piece of equipment with a 3-phase
motor. It's tagged at 200V, with a nameplate that says "rerated to
above
specifications by G.E."

The tool is headed for a new shop that I'm building (of very old
equipment),
so I don't have a dedicated 3-phase solution for the shop yet.

I run a small rotary converter in my current shop, and it does well
enough for my lathe, shaper, and mill. I was gearing up to put a much
larger
rotary in the new shop (have a really nice 15HP idler, and other bits
set
aside), but now I'm wondering if I should really run this one off of a
VFD, since I can theoretically limit maximum voltage on one of those.

Relatively naive physics suggests that up to some reasonable level.
over-voltage really shouldn't be a problem for an induction motor -
short of
stall conditions, it ought to draw less current, and probably run
cooler.

Of course, my naive physics has been known to get me in trouble a time
or two, as well.

Any suggestions, most greatly appreciated - this particular machine is
a fairly sacreligious query here, as it's a 1900's-vintage J. A. Fay
and Egan
woodworking Jointer, but in my defense, there's a Rivett 1030F that'll
be going online right across the aisle, just as soon as I work out
440V 3ph.

Will Ray

P.S. Any suggestions on "soft starting" a 15HP idler, such that I
could
realistically spin it up on my new shop's 200A feed (and preferably on
a
100A branch circuit), would also be delightful.


Reasonable overvoltage is no problem. The no load
losses will increase but it will draw slightly less full load
current and run cooler.

The problem is that, taken too far, the iron losses will
increase as it approaches saturation. Pretty well any motor is OK
at +10% on nominal. Most will tolerate +20% unless you are using
it at continuouse full load at maximum rated ambient temperature.

A useful insurance is to check that the measured full load
line currents are not significantly higher than the rated full
load current.

A sure fire idler soft start system is to use a small pony
motor to prerun it up to half speed.

Jim

On Fri, 28 Dec 2007 14:54:13 -0800 (PST), willray
wrote:

On Dec 28, 2:20?am, wrote:
On Fri, 28 Dec 2007 13:27:12 -0800 (PST), willray
snip
Any thoughts on preventing the
phase-converter electronics from _trying_ to start, unless the
idler is spun up? Not like it's a huge problem if it just blows the
breaker on start up if some idiot (most likely me) hits the start
button
without spinning the idler up with the pony motor, but the purist in
me thinks that using that as a safety is inelegant.

Can't use a potential relay to cut over, since it won't reliably
generate
much until L1 and L2 are provided.

If you use a single phase pony motor to spin up the idler to
near full speed, the centrifugal switch drop out on the pony
motor will signal when it's safe to power up the idler.

Jerry Fosters' comments are also valid. If you go this
route it pays use a good sized, switched in, idler start
capacitor. This is a double win - it both increases the starting
torque and reduces the peak starting current. The increased
starting torque reduces the time duration of the surge and this
makes it less likely to trip the breaker.

Jim

Greetings -

Looking for some advice on running a piece of equipment with a 3-phase
motor. It's tagged at 200V, with a nameplate that says "rerated to
above
specifications by G.E."

The tool is headed for a new shop that I'm building (of very old
equipment),
so I don't have a dedicated 3-phase solution for the shop yet.

I run a small rotary converter in my current shop, and it does well
enough for my lathe, shaper, and mill. I was gearing up to put a much
larger
rotary in the new shop (have a really nice 15HP idler, and other bits
set
aside), but now I'm wondering if I should really run this one off of a
VFD, since I can theoretically limit maximum voltage on one of those.

Relatively naive physics suggests that up to some reasonable level.
over-voltage really shouldn't be a problem for an induction motor -
short of
stall conditions, it ought to draw less current, and probably run
cooler.

Of course, my naive physics has been known to get me in trouble a time
or two, as well.

Any suggestions, most greatly appreciated - this particular machine is
a fairly sacreligious query here, as it's a 1900's-vintage J. A. Fay
and Egan
woodworking Jointer, but in my defense, there's a Rivett 1030F that'll
be going online right across the aisle, just as soon as I work out
440V 3ph.

Will Ray

P.S. Any suggestions on "soft starting" a 15HP idler, such that I
could
realistically spin it up on my new shop's 200A feed (and preferably on
a
100A branch circuit), would also be delightful.

On Fri, 28 Dec 2007 13:27:12 -0800 (PST), willray
wrote:


Greetings -

Looking for some advice on running a piece of equipment with a 3-phase
motor. It's tagged at 200V, with a nameplate that says "rerated to
above
specifications by G.E."

What's the frequency/RPM on the nameplate. 200V motors are often 50Hz.
200V/50Hz = 240V/60Hz = happy motor.

--
Ned Simmons

On Dec 28, 5:09*pm, Ned Simmons inquired:

What's the frequency/RPM on the nameplate. 200V motors are often 50Hz.
200V/50Hz = 240V/60Hz = happy motor.


Nameplate says 60Hz.

Was manufactured in Cinci Ohio, and was eventually found in a barn at
OSU
main campus in Columbus Ohio, so I doubt it crossed the ocean, but of
course, anything is possible.

Other data points: The motor is a custom-frame, integral to the
equipment.
The nameplate "rerated" comment is part of the nameplate silk-screen
text,
rather than an after-label stamped addendum.

Thanks again for any insight!
Will Ray

On Dec 28, 2:20*am, wrote:
On Fri, 28 Dec 2007 13:27:12 -0800 (PST), willray


Looking for some advice on running a piece of equipment with a 3-phase
motor. *It's tagged at 200V, with a nameplate that says "rerated to
above specifications by G.E."
...
P.S. *Any suggestions on "soft starting" a 15HP idler, such that I
could realistically spin it up on my new shop's 200A feed
(and preferably on a 100A branch circuit), would also be delightful.


* * * * * *Reasonable overvoltage is no problem. The no load
losses will increase but it will draw slightly less full load
current and run cooler.
...
* * * A useful insurance is to check that the measured full load
line currents are not significantly higher than the rated full
load current.

I knew there was a reason I liked this place :-) Of course, I can
do that - or at least approximate it - not sure I want to get close to
this thing in an "as designed' full-load context - it's one of those
"toss you across the shop without even slowing the cutter down"
kinds of tools, but I certainly can easily test any sane and
reasonable
load that I'll ever apply.

* * * A sure fire idler soft start system is to use a small pony
motor to prerun it up to half speed.

I've been thinking in that direction (minor difficulty in that my 15HP
idler is a purpose-built idler, and doesn't have a stub shaft outside
the housing, but I expect that I can fix that), but I'm a bit worried
about idiot-proofing the setup. Any thoughts on preventing the
phase-converter electronics from _trying_ to start, unless the
idler is spun up? Not like it's a huge problem if it just blows the
breaker on start up if some idiot (most likely me) hits the start
button
without spinning the idler up with the pony motor, but the purist in
me thinks that using that as a safety is inelegant.

Can't use a potential relay to cut over, since it won't reliably
generate
much until L1 and L2 are provided... No centrifugal starter switch
in the idler... I feel like I'm overlooking something trivially
obvious, but
currently apparently have turned stupid...

I briefly considered setting up a VFD to spin the idler up,
then rigging it to power off without braking, and power up the
converter electronics, but by the time I can afford a 15HP VFD,
I might as well just use it to pretend that it's the utility service,
and
run the whole shop from that - excepting the fact that I don't know
if 15HP is oversize enough to start the 5HP Rivett, nor whether VFDs
do well pushing step-up transformers for the 440 stuff, and blowing
up a 15HP VFD would be, umm, painful...

Thanks again,
Will Ray

"willray" wrote in message
...
On Dec 28, 2:20 am, wrote:
On Fri, 28 Dec 2007 13:27:12 -0800 (PST), willray


Looking for some advice on running a piece of equipment with a 3-phase
motor. It's tagged at 200V, with a nameplate that says "rerated to
above specifications by G.E."
....
P.S. Any suggestions on "soft starting" a 15HP idler, such that I
could realistically spin it up on my new shop's 200A feed
(and preferably on a 100A branch circuit), would also be delightful.


Reasonable overvoltage is no problem. The no load
losses will increase but it will draw slightly less full load
current and run cooler.
....
A useful insurance is to check that the measured full load
line currents are not significantly higher than the rated full
load current.

I knew there was a reason I liked this place :-) Of course, I can
do that - or at least approximate it - not sure I want to get close to
this thing in an "as designed' full-load context - it's one of those
"toss you across the shop without even slowing the cutter down"
kinds of tools, but I certainly can easily test any sane and
reasonable
load that I'll ever apply.

A sure fire idler soft start system is to use a small pony
motor to prerun it up to half speed.

I've been thinking in that direction (minor difficulty in that my 15HP
idler is a purpose-built idler, and doesn't have a stub shaft outside
the housing, but I expect that I can fix that), but I'm a bit worried
about idiot-proofing the setup. Any thoughts on preventing the
phase-converter electronics from _trying_ to start, unless the
idler is spun up? Not like it's a huge problem if it just blows the
breaker on start up if some idiot (most likely me) hits the start
button
without spinning the idler up with the pony motor, but the purist in
me thinks that using that as a safety is inelegant.

Can't use a potential relay to cut over, since it won't reliably
generate
much until L1 and L2 are provided... No centrifugal starter switch
in the idler... I feel like I'm overlooking something trivially
obvious, but
currently apparently have turned stupid...

I briefly considered setting up a VFD to spin the idler up,
then rigging it to power off without braking, and power up the
converter electronics, but by the time I can afford a 15HP VFD,
I might as well just use it to pretend that it's the utility service,
and
run the whole shop from that - excepting the fact that I don't know
if 15HP is oversize enough to start the 5HP Rivett, nor whether VFDs
do well pushing step-up transformers for the 440 stuff, and blowing
up a 15HP VFD would be, umm, painful...

Thanks again,
Will Ray

Just a couple of comments...

On your old 200v. motor... If you were to run it for an extended period and
pull the living daylights out of it, you "might" have a problem. But
jointers tend to get run a couple minutes at a time, so overheating should
not be a problem, even if the physics is "off" just a little. It is not (I
assume) as if you're putting it in a production shop.

On your phase converter. Since this is, as you describe it, a "dedicated"
converter, i.e., the "motor" has no shaft, etc., what you appear to have is
a rotory converter maybe minus the capacitors. Take a look at the RotoPhase
website (http://www.arco-electric.com/) for more information. This whole
thing might just be a lot easier than you expect.

My three horse RotoPhase starts on a 15 amp circuit with no problem. You
should easily be able to start a 15 horse on a 100 amp curcuit (100 amps at
220 volts is about 30 hp...

Of course, YMMV...

Jerry