[chbot] Snubber circuits

[Volker Kuhlmann]

On Wed 21 Nov 2018 12:56:03 NZDT +1300, Trevor Wignall wrote:

Thanks for your summaries!

For an RC snubber the resistor limits the current into the closing
contact when the cap is charged to mains peak. 3.4A @100Ω on top of the
load current.

Going with some common values of 100Ω + 100nF, only the capacitance
value determines the power loss in the resistor. It's 100nF 1.81W, 68nF
1.23W, 47nF 0.85W.

Class Y2 caps are basically always 300Vac, 1000Vdc. Fortunately it
doesn't have to stand the spike voltage.

Through hole carbon film resistors don't really go above 500V working
voltage either, or maybe 1000V peak. That sounds OK, until the datasheet
says "Metal end caps are force fitted to the element prior to spiralling
to value" (TE CFR100J series)... So they would have the same issues as
metal film ones. Wirewound ones are available for higher voltages but
aren't made for transient performance.

Putting at least 3 in series might be wise.

Isn't it fun... ;-)

Volker

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Volker Kuhlmann
http://volker.top.geek.nz/	Please do not CC list postings to me.