Advantages of Closed Slot Stamping vs Open Slot Stamping

[friend81]

Hi Guys,

Recently i came across an information that some manufacturers of Submersible Motors use Closed slot Stamping design in Higher kW ranges over the conventional Open slot stampings. The disadvantage of a closed slot stamping will be the delay in production as it may take upto couple of days to completly sew the coil on its core.

I wonder what could be the advantage of the Closed Slot stamping motor over the one with conventional Open Slot Stamping? Can anyone throw me some light on this issue.

 

[electricpete]

I don’t work with submersibles.

Typical arrangement is semi-enclosed stator slot for random wound windings (allows enough room to feed coils in conductor by conductor) and open stator slot for form wound windings.

Open slot is the only way to get that form wound winding in.

Closed slot has advantage to reduce slot harmonics. It also affects magnetic circuit design in subtle ways I'm not that up on.



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(2B)+(2B)' ?

 

[MagBen]

By designing the closed slot to close to saturation of core material, and so the lower permeaiblity can reduce harmonics in flux density at air gap, decrease the cogging force, however, with some sacrifice in flux linkage due to flux leakage.

 

[jpts]

Semi-closed slots are sometimes used also with form-wound windings instead of normal open slots. Coils are called "hairpin" coils, meaning that the coils are pushed axially into slots from stator ends (instead of radially placing them into slots). Of course this means that coils must be open one one end.

Benefits (as mentioned above) are reduced torque ripple and also reduced need for magnetization current, as the effective air gap becomes shorter. Also rotor surface losses will be reduced, meaning slightly higher efficiency

Basically more or less same effect can be achieved with magnetic slot wedges, which I think is much more common solution with form-wound windings

 

[jpts]

Apparently they are also called "closed-slot coils" or "plug-in coils". Here is one German company manufacturing also these:

http://en.partzsch.de/closed-slot-coils