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From: firstname.lastname@example.org (Paul Mathews)
Subject: Re: Help with snubber circuits
Date: 12 Dec 2002 11:18:15 -0800
NNTP-Posting-Date: 12 Dec 2002 19:18:15 GMT
"John Jardine" wrote in message news:...
> Paul Mathews wrote in message
> > "Jim_12" wrote in message
> > > Hi,
> > However, you can also make the voltage change across the relay
> > contacts less abrupt by paralleling the contacts with a capacitor.
> > This will reduce some types of EMI. Use an X2 capacitor. You might
> > try about 47nF. It's not true that the load has to be inductive
> > (although there always is SOME inductance) to snub contacts.
> > Paul Mathews
> Gets a slightly awkward here, as there would be an additional good and bad
> aspect ;-)
> Adding the cap will actually prolong the bulb life, as there would now be a
> continual 'warming' current of about 4ma running through the bulb (4Vac
> across it) when the switch is off.
> The down side is that the bulb can no longer be considered 'isolated' when
> the switch is off, as the contacts are at mains potential via the cap.
OK. If the relay contacts are the mains disconnection means, then you
need to limit the capacitance to 4.7nF and use a Y2 capacitor. In the
case of medical equipment, leakage currents must be even smaller.
However, it is still true that you can snub contacts switching a
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