3 phase motor help please

[Hotrod56]

I was taking apart this 1940's 3 phase motor and screwed it up. The fan damaged the stator windings and I would like to know if it's fixable. Can I just separate the wires with an Exacto and then add some insulator fluid? I am sure it's not that simple.

not that simple and if it is possible, is there a product that I should use?

Thanks in advance for your help.

 

[itsmoked]

Happy New year Bill!

Too bad you don't live closer I could come by and bother you more readily.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I often think that we could have had some outrageous adventure if we had been young together, Keith.
Seasons greetings.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

It looked to me like you've got open turns and also likely shorted turns in this photo. Personally I'd be very surprised if you have success fixing that yourself. But if you've got the time that's up to you, not much lost if it doesn't work and maybe you'll get lucky and then you can come back here and tell us about it.

Assuming repair attempts are unsuccessful... it was suggested you might replace the motor rather rewind, but I imagine you won't find like-for-like direct replacement for a 1940's motor, which can create some difficulties to work through. Newer motors are smaller frame size for the same rating, and there is a newer NEMA frame system T vs U introduced in the 50's I think. Depending on what you do identify as a replacement candidate, you may be able to find a simple frame adapter. Also we have often seen replacement high-efficiency motors trip the molded case breaker during start... even when the rating and kva code appeared the same the new motors have slower decaying dc which affects that first half cycle... but I imagine you can deal with that if/when it happens. In our plant we would surely rewind rather than fiddle with those types of details, but it depends on your tradeoff of time vs $. (we also have some pretty burdensome paperwork requirements if we install anything other than a like-for-like replacement or rewind).

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(2B)+(2B)' ?

 

[itsmoked]

No doubt Bill!
We'd be on the sheriff's speed dial. They'd probably have some 'codes' for us.

10-29h Caution - severe hazard potential.
10-30 Does not conform to regulations.
10-59 Security check./Malicious mischief
10-80 Explosion.
10-91h Stray horse
10-101 Civil disturbance - Mutual aid request.
11-40 Advise if an ambulance is needed.
11-71 Fire.
11-83 Accident - no details.
904B Building fire.
951 Need fire investigator.
952 Report on conditions.
953 Investigate smoke.
953A Investigate gas.
Code 8 Request cover/backup.
Code 12 Notify news media
12677 Fireworks








Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

As I recall, but subject to correction, you will find the following differences between a "U" frame and a "T" frame.
The shaft will be a different size.
For a given frame size, the "T" frame typically develops more HP.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

As I recall, but subject to correction, you will find the following differences between a "U" frame and a "T" frame.
The shaft will be a different size.
For a given frame size, the "T" frame typically develops more HP.

That sounds about right to me although the details may vary a little bit for specific cases. If you started with a U frame but can't find a direct replacement then you'll most likely end up with a smaller T frame motor that matches the original speed, HP and shaft size... then you can use those adapters I mentioned in my last post to adapt that smaller frame size new motor onto your larger original mounting platform (the adapter accommodates the differences in mounting hole locations and shaft height).

Edit this link shows additional details. It looks like 1940's was before even the U frame motors were around but I imagine you can still find adapter between the pre-U motor base and a smaller T frame motor of comparable rating.

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(2B)+(2B)' ?

 

[waross]

1800 RPM
NEMA Frame------ 254-------5 HP
NEMA "U" Frame-- 254U-----7.5 HP Shaft 1 3/8"
NEMA "T" Frame---254T-----15 HP Shaft 1 5/8"
NEMA "T" Frame---213T-----7.5 HP Shaft 1 3/8"

But this is for TEFC motors.
The motor in question may be an ODP.
In this example, shaft size seems to follow HP rather than frame size, but this is not conclusive from one example.
That motor has probably been rewound within the last 50 years.
As I remember the old "U" frames, they didn't have the insulation paper between the coils when new.
When they came back from a rewind they did have the extra insulation.
In demanding applications, we preferred to use a rewound motor.
We found that a good rewind would take more abuse than a new motor.
Our motors were abused a lot.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

> In this example, shaft size seems to follow HP rather than frame size, but this is not conclusive from one example.

Yes that's my understanding of the pattern in general for a given speed. If you have a given horsepower at a given speed they give you the same shaft size, even when the frame size decreases with the smaller constructions. So you likely end up with a newer T frame replacement that has same speed, hp, shaft size, but smaller frame size (which can be accomodated by adapter). With respect to the table patterns also of course lower speed tends towards larger shaft and frame for the same hp.

> In demanding applications, we preferred to use a rewound motor.

I agree you'll probably have more margin built into a rewound old motor than a new motor of the same rating, regardless of whether there's a frame size difference involved. I see a disappointing trend that some of newer energy efficient TEFC motors run hotter than the originals based on external temperature scans apparently because the OEM trimmed the fan way down to save on the tiny bit of power required to spin that fan. The new winding insulation can certainly handle thse higher temperatures but I think it can push the bearings and their grease into a range that may not be conducive to long life (especially high D*N bearings). I'd gladly sacrifice a tiny bit of efficiency to improve bearing reliability, but EPACT has created efficiency requirements for new motors that has to be met one way or another. As a result we now tend to look for IEEE841 motors for our critical TEFC applications because those include a bearing housing temperature limit in the standard specification as well as a few other requirements geared towards reliability. Getting back to the topic reliability of rewind vs new, an argument for new motors would be stator core lamination insulation... that is not renewed during the rewind process and of course the burnout process for winding removal might challenge lamination insulation further, so it presents one concern for reliability of a rewound motor (as compared to a new motor), but that concern can be mitigated to some extent with a rewind spec that addresses burnout oven temperature (and preferably require the rewinder to give you a chart recording showing that he met your requirements).

HotRod - if you want to post your nameplate info, then I'll be there's a reasonable chance some of the forum members might spend some time digging up replacement candidates for you in the event you want to compare rewind and replacement options.

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(2B)+(2B)' ?

 

[waross]

Hi Pete;
Our plant was only a couple of years old and we were told that it was the newest and most automated high volume sawmill in the Pacific North West at the time.
Designing high speed automated sawmills was a work in progress and our motor tended to be undersized.
Most of our overload heaters were oversized.
The rewound motor and the new motor may have been bought at the same time.
The second burn-out, the rewound original motor would go back into service.
There were discussions as to up-sizing motors in problem locations but a shortage of skilled labour was the stopping point.
Belt drive applications were upsized but coupling driven gearboxes presented a skill gap problem.
While the mill had a good crew of millwrights capable of performing routine duties, there was only one millwright on the crew who had the experience and skill to properly align couplings.
He was worked off his feet and his supervisor felt that he could not be spared to do drive upgrades.
I suspect that the design engineers increased the sizes of their motors by 150% to 200% in the next mill.
At that time charts showing the severity of duty for various industries had an extra column for sawmills as more severe duty than any other industry.
The motor use philosophy could be summed up by the phrase:
"Turn it until you burn it."

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[DAVIDSTECKER]

I have that exact sander!
Mine is pre-1936 as that is when Porter-Cable bought Syracuse Sander Co.
Mine is a 120 Vac, single phase.
I pulled it and a matching oscillating spindle sander out of a dumpster.
Odds are the motor was built with oversized bearings that a newer motor just won't have.
You will be much better off getting it re-would and new bearings installed.
The only thing that would keep it from being re-built is if the laminations are shorted.
You just can't beat that old iron these days without spending a lot of money.
If you go to what was "Old Woodworking Machines.com you may be able to down load the manual under Syracuse Sander if Porter-Cable doesn't have it.

 

[zlatkodo]

Hotrod56
Just completely rewind the stator.
Winding Design and Motor Repair

 

[Hotrod56]

electricpete - the motor is missing the ID plate. Figures.
DAVIDSTECKER - The motor did have different bearings - they were pressed on the shaft, sealed, and then the case side were pressed on - hence the messed up stator - me trying to get it apart. Does yours still work? I am just missing the brass gearset and two of the clamping handles. Part of me just wants to be done and then go and fabricate one from steel myself. Buy a cheap 5hp motor on Craigslist and build around it.

 

[DAVIDSTECKER]

Yes, mine is still running.
All I've done to it is to replace the on switch and clean the ways.
I did tear down and replace the bearings in the spindle sander.
For a 10 HP 2 speed motor my local motor shop charges me about $900.00 for a re-wind and new bearings.

 

[DAVIDSTECKER]

Can you post a photo of the data plate?

 

[Hotrod56]

I just received the red varnish and hope to get to it in the next couple of days. Will let you know how it goes.

DavidStecker - Yep, they are great old pieces. Mine has anywhere from 1/4 to 3/8 of paint on it. Hard to even find any bolts or nuts. Going to take it all down and try to re-do it. Kind of hard in California - cant get a paint stripper that is worth anything and don't want to use a lot of power tools or even a sandblast cabinet as I am 100% sure the pain is lead.

 

[Hotrod56]

Hey Everyone

Just want to update you on the motor.

Separated the windings that were involved, with an Exacto and a pic. Slathered the varnish over the areas making sure to get the fluid to flow in between the wires as much as possible. Put it back together and it RAN. Kept it running for 20 minutes and felt the outside of the motor, which was cool, and then quickly took the motor apart. There was no heat inside the motor on the stater wires. Perfectly room temp. I guess it's all good to go. Thanks for all your help and guidance! I sure appreciate it.

 

[itsmoked]

Outstanding!

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

That was my experience with a similar repair on a 40 HP planer motor.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[electricpete]

Thanks for reporting back your results.

That's a good success by you and good advice by those that advised you to repair it that way.

It sounds like you were able to separate any wires that were shorted (shorted turns usually degrade/escalate very quickly in an ac coil or winding due to high circulating current through the short by autotransformer effect). And apparently there were no open wires?

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(2B)+(2B)' ?