Interesting 3P motor [Archive]

BobL

2nd March 2015, 10:22 PM

Yesterday I picked up this interesting 3phase 3HP motor that I thought some of you might like to see.

Its a Leroy Somer 240V ∆ / 415V Y motor with a independently powered 3P fan
http://www.woodworkforums.com/attachment.php?attachmentid=341435&stc=1

Nameplate
http://www.woodworkforums.com/attachment.php?attachmentid=341436&stc=1

The bigger terminal block is so the motor can be converted between 240V ∆ and 415V Y.
The smaller one is so the fan can be converted between 240V ∆ and 415V Y.

http://www.woodworkforums.com/attachment.php?attachmentid=341433&stc=1

As you can see the fan is pretty beefy (0.12HP ) and it runs at twice the speed of the motor, so better for cooling at low RPMS when used with a VFD.

http://www.woodworkforums.com/attachment.php?attachmentid=341434&stc=1

The motor is from a very large industrial machine that was imported into WA some time ago.
The machine had more than 20 motors on it ranging from 1/10 to ~10 HP.
The guy that sold it to me was working for the company and he said the machine was not required and never used.
Eventually it became outdated and although the company tried to sell the machine they could not get a buyer.
In the end they wrote off the machine as scrap, but before it got sent off this guy took off all the motors and a lot of the control gear and has been selling these through Gum Tree.

Most of the motors (including this one) had toothed belt pulleys with two belt positions/sizes. One of these positions was for a belt to drive a mechanical rev counter to provide feedback to control system which also controlled the motor variable frequency power supplies. He had some on the rev counters there - they looked pretty old school and I assume from all this that it was a fairly old machine.

Most of the motors are Leroy Somer and some were ABB. Some of the bigger (5HP+) motors have large squirrel cage fans driven by 1/2HP 3P motors that ran at a constant 2850 @50Hz for max cooling at low revs.

I'm not sure what I will do with this one. I might have a crack at replacing the 2HP SP on my 19" WW bandsaw but there is a fair bit of modding needed to get it to fit so I will have a think about it first

Anorak Bob

3rd March 2015, 10:37 AM

RayG

3rd March 2015, 01:34 PM

So Bob,

If you did install the motor would you use a pair of VFDs to enable the fan the run at its intended speed and the main motor at variable speeds? There have been a number of discussions regarding simultaneous running of two motors on a single VFD but in the case of this motor, I imagine there would be no advantage of its use over any other motor if a single VFD was used.

Bob.

Hi BT,

I suspect that the fan is a 2 pole motor, while the main motor is a 4 pole, so even if they both ran from the one vfd, the fan will always be twice the motor speed.

Ray

BobL

3rd March 2015, 02:43 PM

Hi BT,

I suspect that the fan is a 2 pole motor, while the main motor is a 4 pole, so even if they both ran from the one vfd, the fan will always be twice the motor speed.

Ray

I haven't tried it out yet but I also assume thats how it works.

cba_melbourne

3rd March 2015, 04:08 PM

So Bob,

If you did install the motor would you use a pair of VFDs to enable the fan the run at its intended speed and the main motor at variable speeds? There have been a number of discussions regarding simultaneous running of two motors on a single VFD but in the case of this motor, I imagine there would be no advantage of its use over any other motor if a single VFD was used.

Bob.

No, that is not how these are used. Only the motor is run by the VFD. The fan runs directly from 50Hz line frequency. It is supposed to provide constant cooling, no matter how slow the motor is running.

PDW

3rd March 2015, 06:51 PM

No, that is not how these are used. Only the motor is run by the VFD. The fan runs directly from 50Hz line frequency. It is supposed to provide constant cooling, no matter how slow the motor is running.

I think that was the point AB was making. You need to run 2 VFD's if you want the fan to run at 50Hz *and* you don't have mains supplied 3 phase 415V power.....

PDW

Michael G

3rd March 2015, 07:02 PM

cba_melbourne

3rd March 2015, 08:06 PM

There is only one cable gland into the terminal box so I think the twice as fast theory wins.
(Before someone suggests running two sets of supply down one conduit, I suspect that would be considered bad (and unsafe) practice)

Michael

Michael, it only takes 2 minutes to drill a hole for a second gland. And its a perfectly safe practice:).

That said, that particular motor in its previous live was probably not used with a variable speed drive. The additional fan was installed to improve cooling, probably because the motor was used in an environment with elevated ambient temperature. If you look at that fan, you see that it is an axial fan. Unlike the centrifugal fan type that is normally used in TEFC motors. It likely provides a greatly increased airflow over the stock centrifugal fan, without taking up much more space.

BobL

3rd March 2015, 08:30 PM

Michael, it only takes 2 minutes to drill a hole for a second gland. And its a perfectly safe practice:)..
There was a couple of feet of old wiring still attached to the motor and there were definitely 2 sets of 3P power (one to the fan and one to the motor) in there

That said, that particular motor in its previous live was probably not used with a variable speed drive. The additional fan was installed to improve cooling, probably because the motor was used in an environment with elevated ambient temperature. If you look at that fan, you see that it is an axial fan. Unlike the centrifugal fan type that is normally used in TEFC motors. It likely provides a greatly increased airflow over the stock centrifugal fan, without taking up much more space.

As I said in my OP there were two toothed pulleys attached to this and on just about every motor the seller had.
The seller was the electrical fitter that pulled the machine down and he said one pulley was to drive something and the other was to a mechanical type tacho which fed back to the VFD. He had a bunch of the old tacos with the corresponding toothed pulleys, and the original VFDs there and they look big and clunky. Very interesting to see all this and I'm glad he rescued it as the gear had never been switched on and was in very good condition

Michael G

3rd March 2015, 09:11 PM

Michael, it only takes 2 minutes to drill a hole for a second gland. And its a perfectly safe practice

Not suggesting that it is not safe practice to mount a second cable gland. I was pointing out that there was only gland into the terminal box as pictured, so it was likely that only one supply was run to the motor. Looking at the terminal block photo again, it looks as if there are jumper cables between the two sets of terminals further supporting the idea.
The reason that I suggested running two sets of cables in one conduit could possibly be considered bad practice was that it could give rise to confusion as to which conductor is in which set - if one set is made safe are you sure the other set has too, and that there has not been any cross wiring. While it has probably been done, I can't see regulators liking it.

Michael

RayG

3rd March 2015, 09:28 PM

Not suggesting that it is not safe practice to mount a second cable gland. I was pointing out that there was only gland into the terminal box as pictured, so it was likely that only one supply was run to the motor. Looking at the terminal block photo again, it looks as if there are jumper cables between the two sets of terminals further supporting the idea.
The reason that I suggested running two sets of cables in one conduit could possibly be considered bad practice was that it could give rise to confusion as to which conductor is in which set - if one set is made safe are you sure the other set has too, and that there has not been any cross wiring. While it has probably been done, I can't see regulators liking it.

Michael

Slightly off the topic, but I commissioned a multiple pump control system a few years back, and the electrician had run the cables, he ran the normal red, white, blue orange circ. there were three pumps, so he did three runs of cable.. and at the other end he connected all the red wires to pump 1, the white was pump 2 and the blue was pump 3... I don't think he had much experience with 3 phase stuff.. I complained, but he refused to change it... :)

The question Bob asked was do you need 2 vfd's, I'm not sure we got enough information for a definitive answer..

Ray

DavidG

3rd March 2015, 10:03 PM

No liability is accepted by UBeaut or the Wood Working Forum's administrators
or moderators for advice offered by members posting replies
or asking questions regarding electrical work.
We strongly advise contacting a Licensed Tradeperson for all electrical work.

WARNING

Information supplied within posts is not to be considered as detailed formal instructions to complete a task.
Members following such information do so at their own risk

RustyArc

3rd March 2015, 11:08 PM

We strongly advise contacting a Licensed Tradeperson for all electrical work.

To be honest, I'd pay more attention to this statement if they spelled "licenced" correctly, that is, the Australian way, as opposed the the American spelling they've chosen to use.

Although that might explain all that American-inspired flag-waving stuff they do around Australia Day.

BobL

3rd March 2015, 11:52 PM

To be honest, I'd pay more attention to this statement if they spelled "licenced" correctly, that is, the Australian way, as opposed the the American spelling they've chosen to use.

Licenced is not a word that exists in the Macquarie (Aussie) dictionary
In the the Macquarie, "Licence" is the noun, "License" is a verb, and "Licensed" is either a verb or adjective.
In the case in question the electrician is being described so it's the latter.

DavidG

4th March 2015, 12:58 AM

Rusty - A licensed trades person has a licence to do the work.

RustyArc

4th March 2015, 08:48 AM

Rusty - A licensed trades person has a licence to do the work.

My unreserved apology - complete brain-fade on my part :doh:

Still curious to know whether you'd get away with running both motors off the one VFD...

GuzziJohn

4th March 2015, 10:32 AM

Still curious to know whether you'd get away with running both motors off the one VFD...

I'm sure you could but at lower frequency the cooling effect of the auxiliary fan is much reduced.

The whole concept of this motor design is to maintain full cooling at reduced motor speed. This is important in some applications (constant torque loads). If you also slow down the cooling fan motor you may as well just use the standard shaft mounted fan.

John

.RC.

4th March 2015, 10:57 AM

I am damn happy I am licecncsed...

BobL

4th March 2015, 10:58 AM

I'm sure you could but at lower frequency the cooling effect of the auxiliary fan is much reduced.

The whole concept of this motor design is to maintain full cooling at reduced motor speed. This is important in some applications (constant torque loads). If you also slow down the cooling fan motor you may as well just use the standard shaft mounted fan.

Sure I appreciate that wired in parallel with the motor the fan will slow down when the motor is slowed down but it should still provide twice the cooling compared to if it was shaft mounted fan. From what I can see it is also a much better fan than a shaft mounted motor so it will be even more effective at low speed than the standard shaft mounted type.

My concern with using it in parallel is not so much at low speeds but rather at high end speeds e.g. if the motor is run up to say 100Hz the fan will be at 5700 rpm and I'm not sure it's designed to do this.

This is why I'm thinking of using it on my WW bandsaw because I am unlikely to run the motor higher than say 75 Hz and lower than say 25Hz.
With my current BS the 2HP motor is underpowered for the relatively long periods at higher loads associated with ripping/resawing and the motor does get quite hot. I'm hoping this higher capacity motor with better cooling will be a better option.

Anyway I will wire it 2up and test it out over the next couple of days and report back.

cba_melbourne

4th March 2015, 12:37 PM

Sure I appreciate that wired in parallel with the motor the fan will slow down when the motor is slowed down but it should still provide twice the cooling compared to if it was shaft mounted fan. From what I can see it is also a much better fan than a shaft mounted motor so it will be even more effective at low speed than the standard shaft mounted type.

My concern with using it in parallel is not so much at low speeds but rather at high end speeds e.g. if the motor is run up to say 100Hz the fan will be at 5700 rpm and I'm not sure it's designed to do this.

This is why I'm thinking of using it on my WW bandsaw because I am unlikely to run the motor higher than say 75 Hz and lower than say 25Hz.
With my current BS the 2HP motor is underpowered for the relatively long periods at higher loads associated with ripping/resawing and the motor does get quite hot. I'm hoping this higher capacity motor with better cooling will be a better option.

Anyway I will wire it 2up and test it out over the next couple of days and report back.

Bob, in my opinion you would be better off to remove that 3-phase fan. Replace it with either a single phase mains, or a low voltage DC fan. Something like an axial box fan (they also make them with round frame). You really want this to be a constant speed fan independent from the motor speed. And you certainly do not want the expense and extra complexity of a second VFD, just to drive a silly fan.

RayG

4th March 2015, 12:40 PM

Rusty - A licensed trades person has a licence to do the work.

It was a licensed electrician who wired up those pumps with 3 red, 3 white 3 blue... just because the guy has a licence, doesn't mean he has a clue... I've worked with electricians for a lifetime. There's good and bad, like all trades, but it's a big mistake to assume that your house wiring type electrical contractor is going to know anything about 3 phase motor controls. Not that's it's all that hard, it's just stuff they might have done once years ago when doing an apprenticeship, and never touched since then.

So with that in mind I modify the disclaimer...

I strongly advise contacting an Electrician with Industrial Experience for all electrical work involving machine tools

:D

cba_melbourne

4th March 2015, 12:43 PM

It was a licensed electrician who wired up those pumps with 3 red, 3 white 3 blue... just because the guy has a licence, doesn't mean he has a clue... I've worked with electricians for a lifetime. There's good and bad, like all trades, but it's a big mistake to assume that your house wiring type electrical contractor is going to know anything about 3 phase motor controls. Not that's it's all that hard, it's just stuff they might have done once years ago when doing an apprenticeship, and never touched since then.

So with that in mind I modify the disclaimer...

I strongly advise contacting an Electrician with Industrial Experience for all electrical work involving machine tools

:D

Well said

BobL

4th March 2015, 12:43 PM

Bob, in my opinion you would be better off to remove that 3-phase fan. Replace it with either a single phase mains, or a low voltage DC fan. Something like an axial box fan (they also make them with round frame). You really want this to be a constant speed fan independent from the motor speed. And you certainly do not want the expense and extra complexity of a second VFD, just to drive a silly fan.

That is a sound option and is what I did with the 3kW Technomotori motor that had a missing independently powered fan.
On the TM motor I used a 240V SP mainframe computer fan which pumps out a lot of air.

I am still curious to see if it works and if it does, as I have all manner of TCs available that I can check temps along the way and decide what to do after that,

Vernonv

4th March 2015, 04:01 PM

... there was only gland into the terminal box as pictured, so it was likely that only one supply was run to the motor. Looking at the terminal block photo again, it looks as if there are jumper cables between the two sets of terminals further supporting the idea.

There was a couple of feet of old wiring still attached to the motor and there were definitely 2 sets of 3P power (one to the fan and one to the motor) in there

Looks like it was most likely 2 separate power sources, as Bob confirmed.

BobL

10th March 2015, 07:22 PM

Finally got round to hooking up a VFD to this motor.

I have 2 spare 4kW HYs in the shed so I hooked one up (lets call that one A) and was immediately alerted to to an issue with higher than usual free running currents
The normal free running current for a 3P 3HP motor is usually about 1A at 50Hz but this one was drawing 2.5A, checked all the connections, all OK.

Then I checked other frequencies and dropping the frequency to 40Hz and the current increased (should decrease) and the motor also started to squeal.

The first thing I did was switched to the other VFD (B) - all good there, low currents, a bit of squeal but not more than I have heard on soother motors.

Then I switched to another motor (an ABB 3HP) and tested this one with VFD A and VFD B.

Here is a summary of all the results.

LSA = the Leroy Somer motor with VFD A
LSB = Leroy Somer motor with VFD B
ABBA = ABB motor with VFD A
ABBB = ABB motor with VFD B

http://www.woodworkforums.com/attachment.php?attachmentid=341906&stc=1
It looks like the motors are fine running on VFD B but not as efficiently on VFD A and the ABB seems to be running better than the LS.
Anyone have ideas why this might be the case?

I have used VFD A as a testing VFD a lot more than VFD B, I wonder if it has undergone too many trips?

Stustoys

10th March 2015, 07:49 PM

ventureoverland

10th March 2015, 08:20 PM

This is very interesting, perhaps more telling about VFDs...

Are all the settings the same on both VFD A & B Bob?

I could imagine current properties being different across motors, but (assuming all settings are the same) Id expect both VFDs to perform the same on each motor.

J

RayG

10th March 2015, 08:39 PM

Time for a little basic physics, leaving aside any weird resonant tuned circuit effects, the current will be the same when the applied voltage is the same, and the motor slip ( or load if you prefer ) is the same. no matter what the brand of vfd or motor.

Since these are all V/F drives, not vector drives, then simply measuring the current with a clamp meter ( do a spot check to make sure all three phases are about the same )
and a simultaneous check on the voltage with an RMS reading meter will show up any differences in V/F curves for the different drive configurations.

So, given all that, what is the likely difference?, I'd guess that it's a fault in the current measurement circuitry is the most likely problem, second most likely would be that there is a phase imbalance and one drive is measuring the current in a different phase?

So, what does the clamp meter and the RMS voltmeter say?

Ray

Marc

10th March 2015, 09:08 PM

If you look back at the origin of the word Licence, it means freedom and also permission. Interesting enough in Italian the same word is used to say a person is "Licensed" as in being allowed to go from a qualifying institution because he finished with the program and also letting go someone as in being fired from a job....so....please if you are in Italy, do not, and I say do not employ a Licensed electrician unless you are really sure what sort of Licence he or she was given ... hu hu:oo:

BobL

10th March 2015, 09:15 PM

Hi Bob,

I assumed you checked all the parameters are the same.*
Were you using the current display on the VSD or your flash meter?

Neither of which would seem to be the full story

Stuart

* yes I feel a bit of a git asking lol

I wouldn't feel any gittishness at all.

Both VFDs have had a LOT of mucking around done on their parameters.
What I need to do is a factory reset and take it from there.

None of the current measurements are done on the 3P side, they are all dome on the SP side of the VFD.

second most likely would be that there is a phase imbalance and one drive is measuring the current in a different phase?
Current is being done on the 1P side and while it may not be absolute it should be OK for comparing like for like
The last time this happened it was a dodgy connection on the 3P side but I have checked these already several times.