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surface crevice on outside of core
2

surface crevice on outside of core

surface crevice on outside of core

(OP)
This is the same family of vertical motors referred to in other motors recently - Westinghouse Lifeline D frame 5800 and frame 5000 series.

We have 18 of these motors - here is an overall picture of one for reference (ignore the annotations left over from another thread)
http://home.houston.rr.com/electricpete/VertMotor1.jpg

If you look through the discharge air baffles at the outside of the stator core, on 8 of the 18 machines you can see something similar to a crevice which goes all the way from top to bottom.  Sometimes in a wandering vertical line, sometimes in a relatively straight vertical line.   Always when you look close you see a jagged patter  similar to this:
http://home.houston.rr.com/electricpete/IM000164.JPG

Here's another picture not quite as good as the last:
http://home.houston.rr.com/electricpete/IM000161.JPG

We can't easily get a better view at this time to see how deep the crevice is, although we may have some opportunity to pull that cover in the near future.

From the appearance (no fresh metal,  paint inside the crevice), it looks like it has been there a long time - perhaps since initial manufacture.  The most likely scenario is that this was a notch which was present on the outside of each of the laminations prior to assembly.  But for some reason these notches (if that's what they are) when assembled don't line up in any regular pattern.

By the way, these motors have operated well during intermittent duty for 20 years.  No vibration problems, no abnormal currents, no abnormal temperautres on stator rtd's, no abnormal insulation test results  

Has anyone ever seen anything like this?  Can you explain why the laminations might be made with notches like this and why these notches might show up in this strange pattern (not lined up)

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RE: surface crevice on outside of core

(OP)
The crevice is about 1/4" wide.  In portions it looks 1/4" deep, but in other portions it might be deeper (tough to tell).

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RE: surface crevice on outside of core

pete,

That is strange. It sure ain't core guide notches. May be you could remove the baffles and take a better picture.

RE: surface crevice on outside of core

Electricpete.
Some notches in laminations are cut as auxiliary for the slotting process. The disk or segments are first punched with those notches used as references for the process jigs, and then the stator slots are punched one by one in an alternating stroking machine. When the package is formed, the laminations are alternated and some inverted 180 degrees to smooth the grain magnetic characteristics due to the rolling direction in the mill and to compensate for possible differences in thickness. The resultant external arrays of such notches sometimes align but in  some other cases they show irregular patterns.

RE: surface crevice on outside of core

(OP)
Thanks guys.  I really don't know much about the core assembly process.

What is a "guide notch" mentioned by edison?

aolalde - I believe what you say but I don't fully understand it.  The pattern seems to me almost random, especially when you compare accross several of the 8/18 motors which have this.  It seems to me as if the notches were cut but then not used as a reference during the slot/tooth punching process.  I could imagine this might be the case if the circulat plate is cut with a notch first, and then moved to a different machine where slot/tooth punching process occurs but does not use the notch as an angle position reference (it doesn't seem like any angle position reference is required as long as the plate are later aligned when stacked to match the teeth/slots of one plate with the plate below).  Or am I way off base?  Any more explanation would be appreciated.

One thing I wonder - does the core plate punching process proceed one plate at a time or several plates on top of each other punched at once?

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RE: surface crevice on outside of core

(OP)
And one more nagging question - On the remaining 10 of 18 machines we don't see any crevice like this.   Why not?

The 8 of 18 don't seem tied to date of manufacture. Also spread randomly amongst the two frame sizes.

Maybe there is a small possibility that the crevice is hiding on those other 10 and we just couldn't find it... but I don't think so.

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RE: surface crevice on outside of core

pete,

A core guide notch is a small arc punched on the OD of the core plates along with the slots. It is provided to assemble the plates with all the punching burrs in the same direction.

Looking at your pics (no chance of better ones ?), aren't the plates too thick for a core lamination ?

RE: surface crevice on outside of core

Electricpete.

Normally laminations are punched one by one and most of the times in several steps. For small motors one single punch could get the lamination, others have progressive steps and very large are made by segments and the slots notched one by one in a kind of machinegun notching press.

Manufacturers can change the type of process for different batches of production. Maybe that is the difference you have noted.

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