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| Interesting spark gap application |
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| Kenyan_guy:
--- Quote from: T3sl4co1l on January 01, 2019, 05:16:14 am ---Yes, this is also often seen on common mode chokes (these are normal mode chokes, for filtering line noise it would seem). It's probably done to improve reliability during ESD testing -- if the inductor's insulation breaks down when zapped, it will tend to fail shorted. Tim --- End quote --- Thanks for the information, yes that reasoning does make sense doing it along the line. I will check the parallel RL characteristics to check the filter cutoff |
| Kenyan_guy:
--- Quote from: MasterTech on January 01, 2019, 07:45:04 am ---What power analyzer is that? and could you post a quick teardown with pictures? --- End quote --- The egauge pro https://www.egauge.net/ I will send more pictures by Thursday. |
| Kenyan_guy:
--- Quote from: coppercone2 on January 01, 2019, 11:09:22 am ---I was always interested in big multi conductor common mode spark gaps, as far as interesting goes. Imagine matching a big spark gap to a entire bus. But the application is extremely interesting, because I ran into a chicken and egg protection problem (do you want the filter taking the edge off for the MOVs and stuff? is the x2 cap stronger? how does that inductor fare? etc). --- End quote --- Its all a catch 22! I believe the reasoning given above of the sparkgap preventing the inductor failing short due toinsulator breakdown above is true. As to the RL filter purpose, all MOVs in the design are ZNR14511U from panasonic whose application tolerances are attached. The purpose of the RL filter may be to act as a high impedance to frequencies above the sensitivity of the downstream components. Example, the transformer, there is also an opamp that performs signal conditioning before passing it off to a 200kHz SAR ADC to sample the state of the voltage on the line for analysis under control of an MCU. I believe this makes sense, unless anybody has a separate view. |
| coppercone2:
i am not sure, but if you have non identical protection components you want a impedance between them (for instance for a GDT to fire before/during the MOV clamp so the MOV does not clamp and prevent the GDT from firing). the RL might also prevent inrush into C but IDK why its before the MOV. it must be protecting it some how? maybe they found high frequencies can break it some how (kind of what comes to mind is induction heating is frequency dependent and it heats the surface of objects but idk if this is relevant its just something that comes to mind when I think about it, maybe because I view the MOV as a grainy bunch of balls that are sintered together). maybe its not frequency specific but they just found that Spark gap, resistor, inductor combination restricts energy and is more robust then the MOV and it ends up lasting longer if you set it up that way. I figure it must be hard to break a inductor and a resistor. I think you would need to test both ways to make sure, it might be very hard to determine what is more protected and against what. it may be that against specific interference functions putting the MOV first would make more sense then after, but I really don't have a clue. also maybe maybe the MOV acts as a frequency mixer for RF and ends up making it even higher in frequency/worse to deal with, so they try to restrict it. normally you want the MOV to blow a fuse though |
| dmills:
The resistor is a classic way to lower the Q of the inductor and reduce the things tendency to turn a fast transient into a ringy mess, nothing more. You see something broadly similar in low voltage DC filters for critical things where the objective to to avoid the resonant peaking (There is some discussion in 'advanced black magic'). Regards, Dan. |
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