I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

On 2010-02-18, Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

My prediction:

The memory card will get full just as the motor spectacularly self
destructs.

i


Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

Bob Engelhardt wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?


I bet it never spins as fast as calculated. I'll even venture it doesn't explode.

Wes

How far back to you plan to be while running this test, and do you have
a video camera? G


Jon

Wes wrote:
Bob Engelhardt wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?


I bet it never spins as fast as calculated. I'll even venture it doesn't explode

I bet that it will spin to close to nameplate x 6.6
and doesn't explode.

On 2010-02-18, Jim Stewart wrote:
Wes wrote:
Bob Engelhardt wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?


I bet it never spins as fast as calculated. I'll even venture it doesn't explode

I bet that it will spin to close to nameplate x 6.6
and doesn't explode.


I think that the bearings will overheat and fail

On Feb 17, 7:03*pm, Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. *I
also have a VFD that will go to 400 Hz. *The recent discussion about the
rpm limits of motors prompts me to see what happens.
...

Did you get the VFD from Bob Neidorff?

jsw

I can add: I've run it at 180 Hz (5400 rpm) without any signs of
trouble. And at no load it runs 1800 rpm @ 60 Hz. Bob

"Bob Engelhardt" wrote in message
...
I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back! But
I thought that I'd give you guys a chance to make predictions. What do
you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I'll bet you rip a hole in the time-space continuum. GOOD, then I don't
have to visit relatives Sunday.

I'll bet you rip a hole in the time-space continuum. GOOD, then I don't
have to visit relatives Sunday.

This would really help me out too. I didn't call the MIL when my honey went
to the hospital.

Karl

Jim Stewart wrote:
Wes wrote:
Bob Engelhardt wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand
back! But I thought that I'd give you guys a chance to make
predictions. What do you think will happen?


I bet it never spins as fast as calculated. I'll even venture it
doesn't explode

I bet that it will spin to close to nameplate x 6.6
and doesn't explode.

But I'd still stay out of the plane of rotation.

In article ,
Bob Engelhardt wrote:

I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

Well, it could well burst at six times design rpm. I would put sandbags
around it, just in case, because the stored energy will be quite large
at near synchronous speed. Energy varies as the square of speed.

What may also happen is that eddy current losses at 400 Hz are very
large in a motor designed for 60 Hz, so it melts instead.

Or both.

Joe Gwinn

On 2010-02-18, Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

I think that the shading coils will fly out of the slots in the
rotor -- assuming that you start it at 60 HZ and then take the speed up
at a rate that it can track. I suspect that *starting* it at 400 Hz
would leave it not able to spin up - but I could easily be wrong.

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I think that the bearings will be fine -- at least until the
rotor spins apart.

Enjoy,
DoN.

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

On 2010-02-18, Joseph Gwinn wrote:
In article ,
Bob Engelhardt wrote:

I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

Well, it could well burst at six times design rpm. I would put sandbags
around it, just in case, because the stored energy will be quite large
at near synchronous speed. Energy varies as the square of speed.

What may also happen is that eddy current losses at 400 Hz are very
large in a motor designed for 60 Hz, so it melts instead.

I would highly recommend to tape a video for such a test. I have not
had a motor ****ty enough to not feel sorry about destroying it, but I
personally would love to see the video if Bob does it.

Bob, if you do this, give the motor some time. I do think that it
should self destruct from one cause or another. I think that bearings
should melt if the motor does not disintegrate before.

Higher speed means more pressure on bearings from centripetal force,
and at higher linear speed, so the heat generation in bearings should
be speed squared, I think. This means that at 6.5 times design speed,
the bearings will generate 44 times more heat.

i

Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

The bearings should hold up to at least 6000rpm above that speed motors
use a higher precision bearing. It also depends on how well the rotor
is balanced. Higher rpm would require better balancing or the rotor and
bearings will eventually self destruct.

Another point is as the frequency is increased the motor reactance
increases which caused a drop in current in the windings. If you really
want to go for broke, set the current limiting for the rating on the
motor but connect the motor for 220 and run it on 440 so that at the
higher frequencies you will still have full current in the windings. The
drive must have at least twice the rated hp of the motor. The motor
will now theoretically put out twice its rated hp. at double the rpm.


I predict that the motor with no load will spin up to the less than
the calculated rpm because of the increased reactance at the higher
frequencies.



John

On Wed, 17 Feb 2010 19:03:32 -0500, Bob Engelhardt
wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?
Bob

A quark-gluon plasma will form which will condense into a micro black
hole which will begin growing in mass as it consumes the Earth's core.
All of we global elites could care less about this, however, as we
have made plans for our evacuation from planet Earth aboard super
secret Nazi designed flying saucer evacuation pods that we have based
in Neuschwabenland in Antarctica (except for Bill Gates who has his
own Space Shuttle gassed up and parked in a silo on the MicroSoft
corporate campus).

I personally, due to my stature amongst the global elites, have
boarding pass number 3, so I will be sure to escape this catastrophe
and flee to our pre-built enclave on Alpha Centauri.
Dave

On Feb 17, 5:03*pm, Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. *I
also have a VFD that will go to 400 Hz. *The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. *What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. *It is older & dirty
inside. *The bearings? *I dunno - it spins pretty easily.

The magic smoke will remove itself from inside as the speed exceeds
what the winding ties will take and they start rubbing on the stator.
Had the same happen to a badly rebuilt starter motor, was sparky, for
awhile! If it's got ball-bearings, they might exceed rated speed,
could be interesting if that happened. Make sure you've got a good
breaker on the circuit when the inevitable happens. Not sure what
happens to a VFD if it starts delivering power into a dead short.

Stan

On Wed, 17 Feb 2010 19:03:32 -0500, Bob Engelhardt
wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Something similar to this gas engine maybe?

http://www.liveleak.com/view?i=fee_1266466975

Dave

Bob Engelhardt writes:

But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

The Euro will collapse and the Dow will sink to 6000 by June.

Oh, wait. What predictions did you have in mind?

On Wed, 17 Feb 2010 19:03:32 -0500, Bob Engelhardt
wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

I'm pretty sure the bearings will not fail. Model airplane engines run
at 15,000 RPM or more for hundreds of hours on ordinary, hardware
store bearings.

I think the copper parts of the rotor will deform, contact the stator
and break. There will be some sparking and smoking before the motor
just stops.

I did the same thing to a 12V DC motor once. It got 300 VDC when an
output transistor in the power supply shorted. Remnants of the rotor
windings were wrapped around the motor in the direction of rotation.
--
RoRo

Engines reverse, full, Helm! Scotty! I need full
power, can you do it?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Buerste" wrote in message
...


I'll bet you rip a hole in the time-space
continuum. GOOD, then I don't
have to visit relatives Sunday.

On Thu, 18 Feb 2010 03:57:31 -0500, lid wrote:

On Wed, 17 Feb 2010 19:03:32 -0500, Bob Engelhardt
wrote:

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Something similar to this gas engine maybe?

http://www.liveleak.com/view?i=fee_1266466975

Dave

would love to see that at 5000 frames/sec.

Thank You,
Randy

Remove 333 from email address to reply.

"Bob Engelhardt" wrote in message
...
I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back! But
I thought that I'd give you guys a chance to make predictions. What do
you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I've actually done this with a 50hp, 1750 motor, but I dialed the speed up
from 0hz, when I got to 180hz, the motor refused to run any faster
and the of the speed of the motor was rising and falling on its on,
no damage to drive or motor.

The drive was an AB 1336 and was located about 100 feet from
the motor, if the drive had been within a few feet of the motor
the results might have been different.

Possibly it wouldn't run any faster due to core saturation.

basilisk

On Wed, 17 Feb 2010 19:03:32 -0500, Bob Engelhardt
wrote:


So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?


I suspect that the motor will get up there without major issues. May get a
quite a bit of noise from the cooling fan. More so assuming that the blades
stall due to flow constriction. if ball bearings, I'd expect them to cope
quite well for a while. May split an end ring on the rotor, but unlikely to
throw a bar, unless it's a very old design.

Bear in mind that if a bearing seizes, it splits an end ring or throws a bar,
it'll jump a way and start spinning in the direction of rotation. Be prepared
for the cables to pull off their connections if possible.

Otherwise, it could be quite boring :-)


Mark Rand
RTFM

On 2010-02-18, wrote:
On Feb 17, 5:03*pm, Bob Engelhardt wrote:
I have a 1 HP 3 ph motor that I don't want & nobody else does either. *I
also have a VFD that will go to 400 Hz. *The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. *What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. *It is older & dirty
inside. *The bearings? *I dunno - it spins pretty easily.

The magic smoke will remove itself from inside as the speed exceeds
what the winding ties will take and they start rubbing on the stator.

This is a three-phase induction motor, so there are no winding
ties on the rotor. Just the welded in copper shorted turns which I
expect to fly out of their slots.

Had the same happen to a badly rebuilt starter motor, was sparky, for
awhile!

That's a DC motor with real windings on the rotor. A different
game.

If it's got ball-bearings, they might exceed rated speed,
could be interesting if that happened. Make sure you've got a good
breaker on the circuit when the inevitable happens. Not sure what
happens to a VFD if it starts delivering power into a dead short.

The VFD will sense the condition and shut down.

Enjoy,
DoN.

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

I have some preliminary results, but my camera battery ran down so I
couldn't run to an end.

So far
- with VFD putting out 360 Hz (its max, not 400 as previously stated)
the motor spins to 10,700 rpm easily & "smoothly". 10,800 is nominal
- ran for 10 minutes before losing battery
- drew .35A
- the closed end bearing warmed somewhat. Maybe to 80F
- running at 10,700 is kinda scary so I bolted it down. I kept thinking
about the rotor jamming & transferring its rotation to the case.
- at 10 sec decel time I was getting over voltage on the VFD's DC bus &
had to increase to decel time

The VFD is rated 2 HP (8A) & the motor is 1 HP, so I should be able to
force it into regions that it won't like G.

I'm going to decrease the accel time as short as I can to see if DoN's
thought about not starting is true. 'Course short accel time is still
not same as applying 360 HZ.

Stay tuned,
Bob

On Wed, 17 Feb 2010 19:03:32 -0500, the infamous Bob Engelhardt
scrawled the following:

I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I'll bet it self-destructs at something like double speed for any
length of time. Flames are likely.

--
"Just think of the tragedy of teaching children not to doubt."
-- Clarence Darrow

Larry Jaques wrote:
On Wed, 17 Feb 2010 19:03:32 -0500, the infamous Bob Engelhardt
scrawled the following:

I have a 1 HP 3 ph motor that I don't want & nobody else does either. I
also have a VFD that will go to 400 Hz. The recent discussion about the
rpm limits of motors prompts me to see what happens.

So I'm gonna' hook up the motor, crank the VFD to 400 Hz & stand back!
But I thought that I'd give you guys a chance to make predictions. What
do you think will happen?

Bob

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I'll bet it self-destructs at something like double speed for any
length of time. Flames are likely.

--
"Just think of the tragedy of teaching children not to doubt."
-- Clarence Darrow


Just another request for video!




--

Richard Lamb
http://www.home.earthlink.net/~cavelamb/

On Thu, 18 Feb 2010 22:02:26 -0500, the infamous Bob Engelhardt
scrawled the following:

I have some preliminary results, but my camera battery ran down so I
couldn't run to an end.

So far
- with VFD putting out 360 Hz (its max, not 400 as previously stated)
the motor spins to 10,700 rpm easily & "smoothly". 10,800 is nominal

Absolutely amazing. How did you measure rpm?


- ran for 10 minutes before losing battery
- drew .35A
- the closed end bearing warmed somewhat. Maybe to 80F

And that was probably from the armature/rotor shaft.


- running at 10,700 is kinda scary so I bolted it down. I kept thinking
about the rotor jamming & transferring its rotation to the case.

Yeah, think "what's in its path?"


- at 10 sec decel time I was getting over voltage on the VFD's DC bus &
had to increase to decel time


The VFD is rated 2 HP (8A) & the motor is 1 HP, so I should be able to
force it into regions that it won't like G.

True.


I'm going to decrease the accel time as short as I can to see if DoN's
thought about not starting is true. 'Course short accel time is still
not same as applying 360 HZ.

Then try short accel + 360Hz.

--
"Just think of the tragedy of teaching children not to doubt."
-- Clarence Darrow

Larry Jaques wrote:
Absolutely amazing. How did you measure rpm?

I have a "laser" tach. E.g.,
http://www.harborfreight.com/cpi/cta...emnumber=66632

Jim Wilkins wrote:
Did you get the VFD from Bob Neidorff?

I don't think - I don't recognize the name. I got it on eBay a couple
of years ago. Bob

Another update.

Here's a short video of it spinning up to 10,700 rpm (some pucker
involved the first time I did this). My previous post said that it spun
up "smoothly" & it was quoted cause smooth is relative. Well, it really
is smooth & here's a video with a jigger of water sitting on the motor
(wmv file, 1.2MB, 10 sec):
http://home.comcast.net/~bobengelhardt/MotorVibe.wmv

I let it run 10 minutes & checked the temp (with my finger tip
thermometer) - the warmest part was the closed end bearing & it was just
a little warm. After another 10 minutes the bearing was a little
warmer. And after 45 minutes it wasn't much warmer than after 20. Note
that the fan did not stall & was doing its job nicely. The case was not
noticeably warmer.

After 15 minutes, the current had *dropped* from .35A to .25A & the
speed increased from 10,690 to 10,715. To me that means that there was
less friction in the bearings as it warmed. By 45 minutes, it hadn't
changed any more.

I keep referring to the 45 minute mark cause that's as far as I got
before my camera battery ran out (it's not a video camera, but a stiil
camera that has video). I'm going to try to find another camera, so
it's not over yet.

Bob

Bob Engelhardt wrote:
Larry Jaques wrote:
Absolutely amazing. How did you measure rpm?

I have a "laser" tach. E.g.,
http://www.harborfreight.com/cpi/cta...emnumber=66632
Shame the inverter doesn't go to higher frequencies as you've currently
got about 80k RPM of head room with that tachometer. It's likely to fail
before that is reached but a concrete blockhouse might be useful for
viewing the test.

On Thu, 18 Feb 2010 19:08:13 -0800, Larry Jaques
wrote:

On Wed, 17 Feb 2010 19:03:32 -0500, the infamous Bob Engelhardt
scrawled the following:



Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

I'll bet it self-destructs at something like double speed for any
length of time. Flames are likely.


Most reasonably modern (=25 years) motors tend to use the same rotor for 1800
as for 3600 nominal speeds. There's no cost benefit for making custom rotors
for variants of little motors.

regards
Mark Rand
RTFM

On Feb 19, 3:02*pm, Bob Engelhardt wrote:
Another update.

Here's a short video of it spinning up to 10,700 rpm (some pucker
involved the first time I did this). *My previous post said that it spun
up "smoothly" & it was quoted cause smooth is relative. *Well, it really
is smooth & here's a video with a jigger of water sitting on the motor
(wmv file, 1.2MB, 10 sec):http://home.comcast.net/~bobengelhardt/MotorVibe.wmv

I let it run 10 minutes & checked the temp (with my finger tip
thermometer) - the warmest part was the closed end bearing & it was just
a little warm. *After another 10 minutes the bearing was a little
warmer. *And after 45 minutes it wasn't much warmer than after 20. *Note
that the fan did not stall & was doing its job nicely. *The case was not
noticeably warmer.

After 15 minutes, the current had *dropped* from .35A to .25A & the
speed increased from 10,690 to 10,715. *To me that means that there was
less friction in the bearings as it warmed. *By 45 minutes, it hadn't
changed any more.

I keep referring to the 45 minute mark cause that's as far as I got
before my camera battery ran out (it's not a video camera, but a stiil
camera that has video). *I'm going to try to find another camera, so
it's not over yet.

Bob

This is far & away the most interesting stuff I've read in this group
in many years. Thanks.

Good video, Bob. Thanx for sharing.

Bob Swinney
"Bob Engelhardt" wrote in message ...
Another update.

Here's a short video of it spinning up to 10,700 rpm (some pucker
involved the first time I did this). My previous post said that it spun
up "smoothly" & it was quoted cause smooth is relative. Well, it really
is smooth & here's a video with a jigger of water sitting on the motor
(wmv file, 1.2MB, 10 sec):
http://home.comcast.net/~bobengelhardt/MotorVibe.wmv

I let it run 10 minutes & checked the temp (with my finger tip
thermometer) - the warmest part was the closed end bearing & it was just
a little warm. After another 10 minutes the bearing was a little
warmer. And after 45 minutes it wasn't much warmer than after 20. Note
that the fan did not stall & was doing its job nicely. The case was not
noticeably warmer.

After 15 minutes, the current had *dropped* from .35A to .25A & the
speed increased from 10,690 to 10,715. To me that means that there was
less friction in the bearings as it warmed. By 45 minutes, it hadn't
changed any more.

I keep referring to the 45 minute mark cause that's as far as I got
before my camera battery ran out (it's not a video camera, but a stiil
camera that has video). I'm going to try to find another camera, so
it's not over yet.

Bob

"Karl Townsend" wrote:

This would really help me out too. I didn't call the MIL when my honey went
to the hospital.

How is she, not the MILstone, doing?
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

Bob Engelhardt wrote:

Larry Jaques wrote:
Absolutely amazing. How did you measure rpm?

I have a "laser" tach. E.g.,
http://www.harborfreight.com/cpi/cta...emnumber=66632


If yours is like mine, you had to stand next to the gren^H^H^H^Hmotor.

Wes

Bob Engelhardt wrote:

Oh - the motor is 1755 rpm @ 60 Hz = 10500 @ 400. It is older & dirty
inside. The bearings? I dunno - it spins pretty easily.

Just out of curiosity, what does it really spin at when the frequency is 60 Hz?

Wes

Wes wrote:

Just out of curiosity, what does it really spin at when the frequency is 60 Hz?

At 60, 120, & 180 Hz it as spot-on at 1800, 3600, & 5400 rpm. I didn't
check again until 360 Hz.

Bob