Flux strength resulting from aluminum backed laminates. 2

[Intermesher]

The desire is to insert a press-fit aluminum tube inside a stator laminate stack on an outrunning PM motor.

http://www.unicopter.com/1952.gif

The intention is to use this aluminum tube as a heat sink for the motor. A heat transfer compound (probably non-silicone) will be pasted between the inner edges of the laminates and the OD of the aluminum tube.


Will the aluminum tube be detrimental to the flux strength in the laminates?


Thanks

 

[waross]

Punching holes in a stack of laminations may have a detrimental effect on the flux or it may have almost no effect. It depends.
You should be asking:
"Will the heat developed by eddy currents in the aluminum tubes cause the stator to run much hotter than if no aluminum were inserted?"
It depends.
Another question may be;
"Will the losses due to possible eddy currents in the aluminum tubes have a detrimental effect on the efficiency of the motor?"
It depends.
And;
"Will shorting the laminations together with conductive tubes in multiple locations cause objectionable eddy currents in the laminations?"
It depends.
And;
"How can we prevent 100% of the non-silicon heat transfer medium from being scraped off when we press fit the aluminum tubes?"
Can't help you there.
This idea may not fly!

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

 

[Intermesher]

Bill

The aluminum tube will be a singular one that fits the large hole in the center of the stator. It will not be a series of small tubes near to and located around the inner circumference.

However, your remarks are probably applicable to both situations. There is obviously much researching and learning still to be done.


Thank you for listing some of the potential problems.

Dave

 

[electricpete]

Typically the stator laminations are effectively shorted by structural elements at various locations of the OD. It is not a problem because there is no path for circulating currents as long as no shorts around the id. I agree that potentially shorting the od will be a big problem.

Eddy currents may flow in the aluminum, and their extent would depend on the thickness of the aluminum as well at frequency of the field. The more eddy currents, the higher eddy losses in the aluminum and greater reduction in the magnetizing flux.

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

 

[waross]

Just blow lots of cool air through the hole.

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

 

[Intermesher]

Pete & Bill,

Thanks for the additional information.

Dave

 

[electricpete]

I think my typo was obvious from the context, but in case it wasn't, I'll offer this correciton in bold
I agree that potentially shorting the od[/b/ will be a big problem.
should've been:
I agree that potentially shorting the id[/b/ will be a big problem.

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

 

[Intermesher]

electricpete

Hi. Yes I am unsure in reference to your use of [OD] and [ID].

This motor is an 'inside-out motor', where the rotor is located outside the stator. The shoe is at the OD of the stator and yoke is at the ID of the stator.

Are you are saying that laminates can be shorted at the yoke [ID] by attaching to the frame or shorting between the individual laminates, but not at the shoe [OD]?

Thanks

Dave

 

[waross]

Laminates are use for counter tops among other things. Laminations are used to build transformers and motors. The reason for lamination is to minimize eddy currents in the core. There may be areas of a core where the laminations may be shorted without causing objectionable currents. There are areas and combinations of areas where shorting the laminations will cause objectionable currents.
But really, this site is for tips, not for the total education of someone attempting a design outside of his field of experience.

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