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From: John Woodgate
Subject: Re: Help with snubber circuits
Date: Fri, 13 Dec 2002 22:32:32 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Fri, 13 Dec 2002 22:54:25 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that R. Lewis
wrote (in ) about 'Help with snubber
circuits', on Fri, 13 Dec 2002:
>"Paul Mathews" wrote in message
>> "Jim_12" wrote in message
>> > Hi,
>> > I have a 240VAC lampflash unit with no snubbing on the relay
>> > would like to add snubbing to this to reduce the EMI.
>> > Can anyone help explain basic snubbing and any snubbing top tips.
>> > The lamp is a 60w regular bulb and the unit flashes this at about once a
>> > second.
>> > Rds
>> > Jim
>> Probably the most effect thing you could do would be to switch the
>> lamp on/off at zero crossings of the mains voltage. A simple way to
>> do this would be to substitute a 'zero crossing switching' type of
>> solid-state relay for the electromechanical relay you are currently
>> 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
>Probably the most effective thing you could do ..... to make this a very
>dangerous set up..... would be to use a 47nF X2 cap as described above.
>I wonder which regulation this doesn't break.
Why do you say that? The relay almost certainly doesn't qualify as an
isolator, so that there needs to be a separate on/off switch as well,
irrespective of whether there is a capacitor across the relay contacts
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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