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#144803 - 01/19/06 01:30 PM dual amperage ratings  
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
New York City
So I'm looking at this old Schuko plug that's been lying at my desk for a while now....and I noticed something.

The rating printed on the face of the plug says
10/16 | 250 (10/16 amps at 250 volts, I assume).

What's with the dual amperage rating? Wouldn't it just make more sense to rate the thing at 16 amps and leave it at that?


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#144804 - 01/19/06 02:07 PM Re: dual amperage ratings  
C-H  Offline
Member
Joined: Sep 2002
Posts: 1,497
Stockholm, Sweden
10A DC
16A AC


#144805 - 01/19/06 02:09 PM Re: dual amperage ratings  
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
New York City
But if there's no DC services anymore, why do they even bother rating the plugs for DC? [Linked Image]


#144806 - 01/19/06 04:31 PM Re: dual amperage ratings  
Rick Kelly  Offline
Member
Joined: Jan 2006
Posts: 60
Iqaluit, NU, Canada
Hi...

There are loads of systems, other then services, that still use DC power. Motor drives... lifting magnets... plating systems... emergency battery banks etc. etc. The DC rating would allow the plug to be used in such a device.

[This message has been edited by Rick Kelly (edited 01-19-2006).]


#144807 - 01/19/06 06:31 PM Re: dual amperage ratings  
aussie240  Offline
Member
Joined: Jul 2005
Posts: 223
Blue Mountains, NSW, Australia
Why would AC or DC be a limiting factor? It's the RMS value of the current that will cause heating of the contacts. Could it be to do with the arc forming when the plug is withdrawn from a live socket?
In any case, using a domestic mains connector on DC is bad and potentially dangerous practice. From what I'm beginning to suspect, it seems to be only in this part of the world where there is an official low voltage DC plug and socket; ie the T configuration Clipsal 402/32, yet I am still horrified at the amount of 240V connectors being used for solar installations, boats, caravans, speaker connectors etc.


#144808 - 01/19/06 08:45 PM Re: dual amperage ratings  
Rick Kelly  Offline
Member
Joined: Jan 2006
Posts: 60
Iqaluit, NU, Canada
You are bang on... it is the interruption of the current that causes the difference.

Interrupting a DC current is a much harder thing to do as there are no "zero crossing points" in the level of the current.

As such... contacts rated for a specific amperage on AC are usually rated lighter on DC. This is true for any device that breaks the flow of current, or that can break it like a plug or a relay contact.

[This message has been edited by Rick Kelly (edited 01-19-2006).]


#144809 - 01/20/06 11:15 AM Re: dual amperage ratings  
Texas_Ranger  Offline
Member
Joined: Dec 2001
Posts: 2,392
Vienna, Austria
There used to be some weird round-pin plug that was commonly used for low-voltage DC in Austria but it went out of production.
On a train I once saw a mixture of standard Swiss 10A and BS 1363 used for 24 DC table lights. The Swiss sockets were 24V DC and 220V AC next to each other... thanks heaven I excaped the sysphus task of replacing all of them!


#144810 - 01/21/06 07:27 AM Re: dual amperage ratings  
pauluk  Offline
Member
Joined: Aug 2001
Posts: 7,520
Norfolk, England
Neither BS1363 nor BS546 connectors have ever carried dual AC/DC ratings in Britain. Mind you, the connectors are rather conservatively rated for either. A BS546 5-amp plug has pins which are pretty similar to the 10/16A Shucko devices.


#144811 - 01/21/06 08:09 AM Re: dual amperage ratings  
djk  Offline
Member
Joined: Dec 2002
Posts: 1,237
Ireland
Were BS546 used with DC though in the past?

The BS1363 plugs, at least the older versions, carried "AC ONLY" warnings on them.

For those of you who have never seen a BS546 plug:

It comes in three sizes (there were other sizes which slipped out of usage)

Triangular pin layout, same as modern UK plugs.

The 5amp version has 2 pins the size of schuko 16A plugs and an earth pin about twice that size. (The sockets, once their shutters are overriden fit Euro plugs pretty much perfectly)

The 15A version pins: 7.05 mm × 21.1 mm. Live and neutral are spaced 25.4 mm apart, and earth is 28.6 mm away from each of them and is signifigantly longer.


#144812 - 01/21/06 02:10 PM Re: dual amperage ratings  
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
New York City
I've heard that the old two-pin version of the BS-546 plug were sometimes used for DC.

You'd have one polarity at one part of town and if you moved somewhere else, or took .... a radio or record player to a friend's house....and they had a different polarity n their mains, you'd have to reverse the plug.

If you had a 3-pin plug, you'd have to undo the connections and reverse them.

Again, this is all just stories I've heard. Don't quote me on this.


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