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Reply to "GOOD CIRCUIT BREAKER?"

Edit:  I see GRJ beat me to this, but maybe this is still helpful.

Mike, I'm also somewhat of a novice with TVS diodes, but I've been studying it and reading the advice of others with more experience and an in depth understanding of Transient Voltage propagation. I'm especially a novice when it comes to working with DCS control and wiring.

What I think I understand correctly from what others more knowledgeable than me have written (and makes sense) is that the closer the TVS diodes are to what they're intended to protect the better they protect it.  The ideal place would be in the trains right next to their sensitive electronics, wired directly across the incoming power wires at the circuit board end.  Additional places throughout the track circuits improve this protection.

Personally, I'm not sure I want to install TVS diodes in every locomotive, because of what would be involved.  I'm considering installing my TVS diodes at every power drop at the track end, adjacent to the track and maybe (or maybe not) in certain locos.  There is some risk by not installing the TVS diodes in the locos because of the way the high frequency transient electrical waves created by derailments "bounce" back and forth along all conductors attached to the track.

Put another way, as I understand the principle, even though a TVS diode may be clamping the voltage to a safe level at the exact spot where it's connected, inches away the voltage can oscillate substantially higher for brief periods of time until after the "instant" breaker removes the current driving this wave and the TVS diodes working in concert can sufficiently attenuate this "bouncing" voltage wave.  Maybe this isn't a 100% technically correct way of explaining the transient wave propagation, but I hope it at least gives you a better idea of what we're trying to deal with.

If I've made a misstatement, or if application of TVS diodes in a DCS environment would differ, someone else please enlighten us.

Last edited by SteveH

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