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Re: [TCML] BPS Testing

Hi Gary,

Lau, Gary wrote:
As I had mentioned, I had measured the NST's short circuit current and found it to be not far from the faceplate rating of 60mA (I don't recall the exact number).  Low voltage side (primary?) short circuit current???  I don't think that winding resistance measurements would indicate much.  I have not tried measuring the open-circuit voltage as I have no reason to suspect that it differs significantly from the faceplate rating.
Well, then it's certainly a 60mA unit. I like to measure my NST's data as much as possible to know what I'm working with, especially for these type of situations. Winding resistance does tell us impedance information, although it doesn't change a lot from the face place equated impedance (but a little). Gerry Reynolds helped iron out the NST impedance with Javatc allowing users to measure winding resistances (which almost everyone can easily do) and helps get just a little closer to reality.

Today I looked at the nearest break to break occurrence with my 15/60 test. The break occurred 1.1ms after the quench of the first break. This would require a 400mA continuous charge to get back up to the arc voltage in order to break 1.1ms later. That just seems much to ask from an NST and I'm not sure ferro resonance will do that (maybe). I know ferro resonance causes extreme voltages in cables and equipment, but there is usually a good reason for it (it's just not that easy to find the reason and that's where it gets difficult). Transformer saturation is one of those situations that can cause it.

I also looked at the entire 12.7 second measurement data today and counted number of "soon after" breaks. I don't have the info in front of me, but it was something like 83 occurrences. If I removed those 83 from the total 998 breaks during that period, bps equated to 72. There is something here that's real. It shows that charge time of caps up to the firing voltage is as it should be, but there are these series of breaks that occur soon after for some reason (either ferro resonance or possibly a partial discharge and then re-ignition). It has to be one of those two reasons.

Looking forward to your 140VAC measurements!
I'm looking forward to it also.

Take care,

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