Die Cutter Motor Issue 1

[itsmoked]

Called out to a machine that isn't starting reliably.

I get there and find it powered with a rotary phase converter (RFC). It has a rotary lever power switch on the front.

Fire up the RFC. Then I crank the lever switch and I can hear things spinning. But the gal tells me it's not sounding right and as she tells me this the lever switch trips back off. Huh...

I open the wall mounted disconnect box that feeds and receives the RFC output and passes it to the machine.
I measure the output. 244, 245, and 245V.

I pull the stamper's covers off and find the lever switch is a breaker, probably doing its job.
Looking at the motor I see this:

I don't see any way this thing can run on 240V. Do you?

Can I boost the output of a RFC?
Can you do it with only 2 or is this a case where you need 3 boost transformers?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Check the price of one transformer and a VFD.
If you go with the two transformer solution you may want to consider connecting the open-delta Auto-transformer so that the solid L1 and L2 are across the open delta.
That will give you symmetry.
Is this a new install or has the machine worked in the past?
What are the specs of the RFC (Rotary Fase Converter? Not to be confused with RPC, Reverse Polish Convention. grin ).

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

 

[ScottyUK]

Hi Keith,

See if the winding star point is accessible. You probably need to remove the endbells to find it, or it may be buried. That 380/440V star winding would make a 220/250V delta winding which would work perfectly with the phase converter you've got.

 

[waross]

Good call Scotty.
Let's hope that it's not already in delta.
Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[ScottyUK]

Hi Bill,

I think the nameplate shows a 'Y' after the voltages - maybe Keith can confirm. A delta on such small motor would be quite unusual in my experience.

 

[mgtrp]

Are the 240V voltages that you're measuring phase-phase or phase-neutral? 240V phase-to-neutral is 415V phase-phase, which would match well with this being an IEC-rated 380-440V motor.

 

[itsmoked]

What are the specs of the RFC (Rotary Fase Converter? Not to be confused with RPC, Reverse Polish Convention. grin ).

Nice catch Bill! Funny how my brain works..

Scotty.. This picture is cast into the pecker head cover:

And... It is wired as DELTA now - The bottom diagram.

Does this mean the motor is actually:
440Y 220D @ 60Hz
and
380Y 190D @ 50Hz
or do I have it wrong.(?) How is it 220D/250Dv?


mgtrp; Those measurements are across L1, L2, L3 in the bottom diagram seen above. Phase-to-faze.

One other data tid bit that might mean something is: The currents are 3.5A, 3.5A, 4.2A which all are higher than the 3.2A suggested by the plate for 440V service.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Smoked,
Any funny smell - like yours?

You can't have what you suggest:

"(Does this mean the motor is actually
440Y 220D @ 60Hz
and
380Y 190D @ 50Hz
or do I have it wrong.(?) How is it 220D/250Dv?"

Neither. Wye/Delta voltages are always a factor sqrt(3) Never anything else.

I happened to visit a guy at the Thrige-Titan (ABB now) factory in Odense some one month ago. I'll try and get in touch with him. He has been with TT forever. If there is any other issue than high load or a smoked winding, he will tell you. But he won't be available until Monday. If we are lucky.

Talking about RPC (or RPN, as I know it), do not confuse with RPM (double grin)

And, for good measure: Did it ever run? Or is it something the customer found in his back-yard and is now trying to blow life into?


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Hi Gunnar!

That would be great to get some inside news. I looked a lot of places on Mr. Web and could find nothing on any T-T motors except some "Square Motors" or maybe that was my Asea hunt.

The square root makes a heck of a lot more sense. Thanks for clearing that up!

This thing has run for more than a decade in this spot. It has a weird hydraulic pump driven by motor that the motor stands up on. With the cover off you look in at Lake Hydraulic everything is sitting in. The pump has this 15 inch diameter four inch tall cast iron rotor you can see thru a window. Heck, you can stuck your finger in the window spin the rotor - easily.

The third time I tried the motor it started up with a turbine whine that lasted about 6 seconds and the gal said across the room, "That's what it's supposed to sound like!!". Running like that is where the above current measurements were taken. We cycled the machine several times with no issue.

It had worked flawlessly until last Tuesday when it failed to complete the start several times until the lady gave up. It failed when she showed me on Friday twice. But didn't fail me 20 minutes later on the third try and didn't fail the next two times.

I was hoping it was under volted but that's not looking so promising now.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Hi Keith,

That motor isn't young, it's about 40 years old based on the period when Thrige passed through ASEA's hands in the 1970's.

A few tests on the motor would be worthwhile. Split the links at the motor, megger each phase to earth and between each pair of phases. Measure winding resistances which should be well balanced, and insulation resistances should be very high.

If the motor is OK then it's almost begging for a little VSD. My guess is the problem is in the converter itself and not the motor.

 

[Skogsgurra]

Class B insulation. Me not think it can survive a VFD.

Could be something non-electric. We sparkies are often blamed for just about anything. Oil viscosity, lower temperature and plugged filters may be the culprit(s). Sump filters are known to clog.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ScottyUK]

"We sparkies are often blamed for just about anything."

Presumed guilty until we can prove our innocence!


Fair point on the class B insulation Gunnar, although a replacement motor isn't exactly a high value item - a decent brand machine would cost about £350GBP and an anonymous one perhaps half that.

 

[dArsonval]

One can test the electrical integrity of the motor as Scotty is suggesting.
Yet, the device works electrically as was confirmed when it actually ran the way
“the lady” said it was supposed to sound like.
You’ll likely find nothing wrong with the motor winding or the rotary phase converter.

Something [Mechanical] is now highly suspect if it has been in operation as long
as mentioned. Every single screw connection on the capacitors in the phase converter,
or quick connects should be looked at and tightened.

The tolerance of the motor’s bearing fits will also be something to consider because
over time they do indeed open up as they “work”. And if the motor (the size it appears to be)
is driving a large cast iron rotor… it’s conceivable it comes to a certain resting point when
it’s shut off where it won’t start again.

Reaching in to turn the rotor may have jostled something. I doubt the motor has a cracked rotor,
but that’s a possibility as well.

If absolutely everything electrical checks out, it’s something mechanical.
Finding what that “is”, will mean taking it off the machine for a complete inspection.

John

 

[itsmoked]

I'll be revisiting the thing tomorrow and will megger the three windings to each other and to the case and will also measure the winding resistances to see that they match.

I'll also (hopefully it with start) watch the starting current over the extended 6 second wind-up. Seems there is a massive flywheel running the pump which probably caused the long startup. The machine cycles pretty fast so maybe they use a smaller motor and store KE between punches.

If the measurements look good and connections tight I'll declare it mechanical and have a hydraulics servicing guy come by and drain the "lake" and check the intakes and any filters.

I don't actually know what a clogged inlet on, say, a gear pump does to the motor load. A centrifugal pump would likely unload with a clogged inlet (and cavitate like mad) but a hydraulic pump??

Here's a picture for you folks to chew on. You can see part of the little window I mentioned into the rotor just behind my clamp-on.

Oh, and you can see a site-glass into The Lake just below the opening into the machine.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

It's the opposite with a gear pump, Smoked. Stopping flow stops the pump. Narrowing the channel brakes the pump.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.