Film-backed insulation (mylar) on 4kv+ motors? 2

[electricpete]

Does anyone have good or bad experience to report regarding the use of film-backed mica tape insulation in either strand, turn or groundwall insulation of motors rated 4kv and above?

This would include mylar, kapton, and polyester (not polyester resin... polyester backing).

I have heard that this type of material may be susceptible to degradation under voltage stress, disappearing and creating voids. Also doesn't permit global vpi resins to penetrate well?

 

[teco]

electricpete:- yes we have had problems with mica backed tape and kapton tape but only on "RANDOM" wound macines up to 6.6kv.we found voids were created in the end windings and when the end windings were half lapped taped to include the slot liner little if any varnish penertration even under v.p.i.was found. hence rapid deteriation under d.o.l. starting was exsperienced.
to over come the problem use mica / glass backed tape and close spiral tape, this will allow varnish penertration.
we have not had a problem with full pressed moulded coil systems.
suggest you contact jones stroued insulation systems uk.
kind regds.

 

[electricpete]

TECO - Thanks for the outstanding info. I did have the privelege to talk to Rigsby Kavanaugh from your organization who was EXTREMELY helpful/knowledgeable.

If I'm understanding your response correctly, the only problems you've seen with film insulation are on random wound machines... where it impeded the vpi impregnation.

Is it correct to assume that you've had favorable experience (impregnatiion) when film-backed insulation was used as strand/turn insulation for form-wound machines?

Thanks!

 

[teco]

electricpete:- we only use semi cured mica tapes on form wound coils were the slot section is is pressed and cured.the only time we use mica film tape is on the connection ring . to date we have not had any problems.
we tend to be a bit old fashioned and follow proven methods.
kind regds.