Searching \ for '[EE:] Switch A rating extrapolation?' in subject line. ()
Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=switch+rating+extrapolation
Search entire site for: 'Switch A rating extrapolation?'.

Exact match. Not showing close matches.
'[EE:] Switch A rating extrapolation?'
2004\01\24@182335 by

Hi,

If a switch contact is rated 0.5A @ 125VAC, what is the correct way to
calculate its rating @ 5VDC?

Thanks,
Colin

_________________________________________________________________
Protect your PC - get McAfee.com VirusScan Online

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

> If a switch contact is rated 0.5A @ 125VAC, what is the correct way to
> calculate its rating @ 5VDC?

Can't help with a specific calculation (but I'm sure it has a lot to do
with the resistance of the contacts and joules / energy)

Looking through the C&K and MEC catalogues, a typical example
for a small toggle switch is 0.25A 125VAC / 9W AC / 6W DC which
I infer from that  you de-rate by 1/3rd from AC W to DC W

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

>From: Jinx <joecolquittCLEAR.NET.NZ>
>
> > If a switch contact is rated 0.5A @ 125VAC, what is the correct way to
> > calculate its rating @ 5VDC?
>
>Can't help with a specific calculation (but I'm sure it has a lot to do
>with the resistance of the contacts and joules / energy)
>
>Looking through the C&K and MEC catalogues, a typical example
>for a small toggle switch is 0.25A 125VAC / 9W AC / 6W DC which
>I infer from that  you de-rate by 1/3rd from AC W to DC W

Looks good to me.  Thanks, Jinx.
Colin

_________________________________________________________________
Help STOP SPAM with the new MSN 8 and get 2 months FREE*
http://join.msn.com/?page=dept/bcomm&pgmarket=en-ca&RU=http%3a%2f%2fjoin.msn.com%2f%3fpage%3dmisc%2fspecialoffers%26pgmarket%3den-ca

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservmitvma.mit.edu with SET PICList DIGEST in the body

> > > If a switch contact is rated 0.5A @ 125VAC, what is the correct way to
> > > calculate its rating @ 5VDC?

> >Can't help with a specific calculation (but I'm sure it has a lot to do
> >with the resistance of the contacts and joules / energy)

> >Looking through the C&K and MEC catalogues, a typical example
> >for a small toggle switch is 0.25A 125VAC / 9W AC / 6W DC which
> >I infer from that  you de-rate by 1/3rd from AC W to DC W

That MAY be a good starting point but I'd be careful drawing conclusions
from a single data point.

There are a number of factors involved (and I certainly don't understand
them well). Dissipated energy is important BUT things like arc quenching can
make a vast difference to performance. An AC switch opening at the sort of
rate you would get with finger operation is liable to quench an arc in a
maximum of one half cycle of the switching frequency. When switching DC,
slow opening can lead to an arc over an extended period. For this reason
switches which are expressly intended for high energy per size DC switching
will often be designed to snap open to minimise arc time. Most common main
switches (at least in NZ equipment) are not provided with snap open
operation.

RM

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestmitvma.mit.edu

> > >Looking through the C&K and MEC catalogues, a typical example
> > >for a small toggle switch is 0.25A 125VAC / 9W AC / 6W DC which
> > >I infer from that  you de-rate by 1/3rd from AC W to DC W
>
> That MAY be a good starting point but I'd be careful drawing conclusions
> from a single data point.

I wasn't too happy with my answer. It seemed a little simplistic, which is
why I went looking for more info. Hardly surprising then that, given the
number of switch types and applications, the sensible upshot is that you
should seek out the proper switch for the job, especially for power. But
for low-power (eg signal) most of us just pop in somewhere and pick
up any old switch based on looks, size, poles and price

> When switching DC, slow opening can lead to an arc over an
> extended period

The switch on my brother's 12VDC compressor had a melt-down
through arcing and bad design. It was one of those plastic rocker
switchers, rated at 3A for a 2A motor. It got knocked 1/2 on and
just melted

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestmitvma.mit.edu

More... (looser matching)
- Last day of these posts
- In 2004 , 2005 only
- Today
- New search...