SEM thermal test

Hi All,

I have had a lot of e-mails regarding the SEM failing after they have run at a high temperature this indicates poor quality enamelled wire, so I have been testing one of my rewound stators to see if temperature had any bearing on it's performance. I have not tested any of my ignitions in this manner before so I thought it would be interesting to see what the out come would be.
The only thing I don't know is what temperature they run at when on the engine, I have run this ignition for a total of 38 hours so far varying in temperature from 90 degrees C to 185 degrees C. The class of wire I use has a threshold of 200 degrees C, So I am going to keep testing it until it dies or catches fire which ever comes first. I'll let you all know the out come at some future date.

Sparks

Hi Dale,

Yes your correct about the vibration been a killer, there are basically three things that will kill an ignition stator vibration heat and moisture all three will have the same end result if given in large quantities.

The main problem with these windings is cheap enameled wire, what I see when I strip the coil nearly always the problem is at the first row of windings on the bobbin, you can see where the enamel has deteriorated and there is small green specks where the copper has oxidised and eventually fractures.

The wire I use is of high quality enamel and can withstand higher temperatures. Before rewinding each bobbin I put one layer of a woven tape, we use in the winding trade this gives the winding a more cushion effect rather than straight on to plastic bobbin. The other thing you are up against is the thickness of the wire 0.071mm is the finest I have ever used on stator source coils, but I don't think that this is the problem to why they fail. I have lost count of how many SEM stators I have rewound up to press I have not seen one back, so all I can say it must just be the quality of the wire or lack of it that make then unreliable.

Regards

Sparks
www.uk-motoplat.com

Re:SEM stator thermal test

Hi All,

Well my rewound stator that I have had on test has finally thrown in the towel.
After extensive testing under very duress conditions hot cold and wet total hours covered was 326.
After removing all the potting compound I found the fault wasn't down to the windings but the copper tracking that the wire ends are soldered to had shorted together, I removed the carbon where the tracking had occurred tested it on the meter test OK put it in the test rig and low and behold it sparked up as normal.
Even though it only covered 326 hours the abuse it received was rather excessive and I would think one of my ignition under normal running conditions will have a lot longer life.
Comments most welcome.

Regards

Sparks.

Hi Parsko,

Good comments there, I think the reason vibration kills them is that the wire is wound directly onto the plastic bobbin and the high frequency vibration against the wire and plastic bobbin eventually kills the windings open circuit, some of the Jap ignitions suffer badly from this especially the two strokes.But no this is one force I have not put on my test stator, even though I can spin them up to 14000. RPM + I can't replicate the four stroke vibration
I wrote in one of my earlier postings that I put one turn of woven tape around the bobbin first to give the windings a cushioning effect.
It would be a good test to one in the engine that Dale mentioned in an earlier posting to see how it faired against vibration. But I can't stress enough how poor the original enameled wire is this is the biggest reason why they fail.

Sparks.