EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Kjelt on July 13, 2015, 06:32:36 pm
-
just read this datasheet from 3M for a ribbon cable they sell.
What I found astonishing are the specifications of this cable, in the USA and Canada it is rated for 300V but for Europe less than 50V a factor 6 :wtf:
So is this correct and are the insulation requirements in the USA and Canada so low or what?
-
Seems much more likely that the EU "standards" were set by faceless government bureaucrats and not established on any actual scientific or engineering principles.
-
In the USA mains cords are allowed to have a single layer of insulation over the conductors (i.e. "figure 8 zip cords"). In Europe you don't see this any more. I suspect this would be the difference in the voltage rating: single insulated vs double insulated.
-
The first thought that comes to mind is maybe the specification is different for the EU and American tests. As an example, one may specify the breakdown voltage with little or no current being passed and another may do the test with the cable under maximum load. We even see differences here in the EU, when specifying maximum current capacity you will see one value for free air/cable trays and another (lower) current value when a cable is used in conduit or trunking.
-
I suspect it's just a data cable and they did simply not test the IEC/EU standards for mains voltage, so they limit it to SELV.
As IanB noted all mains carrying cables the user can touch must be doubly insulated here, but single insulation is of course ok for internal wiring.
-
it is probably just because above 50VAC/75VDC you have to comply with the EU low voltage regulations
-
Seems much more likely that the EU "standards" were set by faceless government bureaucrats and not established on any actual scientific or engineering principles.
And there ain't any of that breed over in the US?
Interesting.
-
American approach: Specify the guaranteed failure point. Use your judgement about how high to run it.
European approach: Specify the guaranteed safe operating point. Use your best guess about the margin past this point.
-
American approach: Specify the guaranteed failure point. Use your judgement about how high to run it.
European approach: Specify the guaranteed safe operating point. Use your best guess about the margin past this point.
yeh something along the lines of: functional rating vs. safety rating
-
Seems much more likely that the EU "standards" were set by faceless government bureaucrats and not established on any actual scientific or engineering principles.
And there ain't any of that breed over in the US?
Interesting.
Oh yes, of course there are. And we are becoming more "European" every year. Why here in my corner of the Colonies, we "love" our government so much, we have an EXTRA layer of bureaucracy. 6 layers of government if you count the UN.
But I think @Tomorokoshi had the best explanation.
-
Double insulation in the US is only required for Class II appliances that don't connect to earth ground.
For trays, etc, we call that plenum and there is a requirement to use plenum wiring (even for ethernet) but that only has to do with fire retardation, so that the wiring doesn't spread the fire faster.
-
Plenum cabling is frequently a lower cost conductor arrangement (e.g. solid core) for fixed installation that doesn't have to meet (e.g. multi-stranded) flex requirements needed in 'flex' applications.
In CAT-x terms - plenum cabling vs patch (flex) cables.
-
I should have stated "in the US" twice, in here it has to do more about fire safety than anything else.