Micromotor repair

[EngRepair]

We need to fix that. The stator of a very old micromotor for dental laboratories was defective.

Fortunately, only one of the 3 terminals lost contact. That has been fixed and the motor is now working well.

As can be seen, it is a three-phase motor powered via a VFD for speed control up to 50,000 rpm. Probably it is 2 pole, 3-phase winding. The number of slots could be 3 or 6 or more.

But I wonder how to disassemble such a motor? Probably I need some special tools.

Does anyone have experience with this?
What does the rotor look like? What are the bearings like because the motor runs very quietly?

 

[RedSnake]

Not sure if it can be this one.

https://www.manualslib.com/manual/1682305/Kavo-Centerline-Ewl-4011.html#manual

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[EngRepair]

Thanks, RedSnake,
It's a lot like my case. It may even be the same manufacturer.
The rotor appears to be a squirrel-cage type.
Is this motor rewindable at all?
It would be nice to hear from someone who has already had the opportunity to disassemble motors like this.

 

[waross]

Look for a set screw, item 5 in RedSnake's graphic.
The motor may be assembled with interference fits and crimped joints. It is possible that it may only be destructively disassembled.

Fortunately, only one of the 3 terminals lost contact. That has been fixed and the motor is now working well.

You were very fortunate.
I suggest that you file away any information that you can get, but as long as the drill is running, don't try to take it apart.
Somehow the age and general description reminds me of a very old dentist's chair that I was able to repair in a clinic in La Ceiba.

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

 

[electricpete]

> What are the bearings like because the motor runs very quietly?
I see one deep groove ball bearing piece #2. I don't see any bearing on the other end. Maybe it's just some kind of sleeve / bushing on the other end (?)

There's always a risk taking apart something you've never taken apart before.
As our maintenance department is fond of telling me: "If it ain't broke, don't fix it!"

=====================================
(2B)+(2B)' ?

 

[waross]

Nice find on the motor cutaway, Anna.

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

 

[EngRepair]

Nr. 6 is also ball bearing. They could be the ceramic type.

 

[3DDave]

That diagram is not of the OP motor.

 

[RedSnake]

As our maintenance department is fond of telling me: "If it ain't broke, don't fix it!"

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein