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Old 12-29-2011, 07:42 PM   #200
JoelWisman
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Location: STL, MO, USA
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Ok, finally heard back from someone thats been helpful in the past.

Polyester-imide is what the F twin rotax stators are insulated with.

"Polyester-imide magnet wire is insulated with a Class H modified polyester resin. It has excellent thermal endurance, solvent resistance and exhibits a low coefficient of friction to improve windability. It requires mechanical or chemical stripping."

It is rated for a maximum temperature of 180C

Since theres some reference to Aprilia here, and it's something I have some new connections with, their 650 single and 1000 CC Rotax V twin stators are insulated with Polyester A / I Topcoat.

"Polyester-amide-imide magnet wire is a two-part insulation consisting of a modified polyester basecoat with a superimposed amide-imide outer coating. This wire exhibits exceptional windability, heat shock resistance, and ability to withstand overloads. Chemical resistance to most solvents and insulating varnishes is extremely good. It is not softened by refrigerants and extractions are essentially zero."

It is rated for a maximum temperature of 200C

On A side note, I don't remember seeing many charging system problems on old BMW F singles, which were actually built by Aprilia and rebadged by BMW.


I have never had any education specific to Parallel PM regulators (shunt type, stock for all of these) Or series PM regulators. Most of my education came from the automotive industry which does not use PM alternators.

That said, as an industrial electrician I had plenty of training with PWM motor controls, which seem to me to be similar to series PM regulators, and the problem is the large voltage spikes causing Partial Discharges (PD) in the coils or complete flashover and burn out.

Maybe theres some sort of new control technology, but any time we used PWM's, we wanted a motor with a magnet wire that said something like this "Polyamideimide For inverter duty applications, this insulation is designated for use in motors that may be subject to voltage spikes".

Neither the stator insulation BMW or Aprilia uses is known for spike resistance but particularly NEMA NW30, or Polyester-imide, what the F twin uses, is just plain bad at dealing with voltage spikes.

This may not be relevant. Perhaps series regulators some how avoid spikes, or maybe they aren't high enough to offset the benefits of lower heat. I simply don't know.


I do know that for me it wouldn't have mattered cause I use nearly all 400 available watts the F8 had to deliver either way.

Also 180 and 200C magnet wire is upper end to begin with and may explain why rebuilds aren't lasting long as 155C class is the usual to rewind car alternators with.



Without going too exotic...
Temperature Class: 240 C
Insulation Type: Polyimide-ML
NEMA Specification: MW 16C
Federal Specification: JW1177/15
IEC Specification: 317-7
Insulation Characteristics:
ML is a film coated magnet wire made with polyimide resin. It is a Class 240 C thermal life insulation with exceptional resistance to chemical solvents and burnout. It will operate at a temperature up to 240 C. The outstanding cut-thru of over 400C and its ability to withstand excessive overloads extends the use of magnet wire in extreme conditions. ML is unaffected by prolonged exposure to varnish solvents and it's compatible with virtually all systems


But I can say from experience, winding the above shit without cracking or bunching it is a PITA.

Sorry, still no answers, but more information.

P.S. Potting and varnishing are not the same thing. Once the varnish fails and causes shorts, the resultant short will cause the stator magnet wire to exceed 800C and sometimes even melts the copper so like 1100C. Potting just keeps the magnet wire from moving around and abrading.

P.P.S. Denso makes the PM rotor and stator of these and many many other motorcycles, but they are a goliath company with a tun of off the shelf products and ability to cater to any buyers design. In quality control and design, Denso makes Bosch look like a bunch of fools.
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I love and miss you Jeneca and I'm sorry.

JoelWisman screwed with this post 12-29-2011 at 07:47 PM
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