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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 19th Jul 2017, 1:16 pm   #1
Voxophone
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Default Y2 rated capacitor question

Hi All,

I'm currently looking to replace some caps connected to the gram and aerial sockets of a radio.

My understanding is that a short circuit failure of a capacitor in this position could potentially pose a shock risk and hence a Y2 component would be selected. The sticky thread at the top of this section states the same.

However, looking at Y2 rated caps on RS I see the following warning in all of the listings:

'Capacitors are designed for connecting directly across a mains supply but should NOT be used in positions where failure of a capacitor would expose anybody to electric shock.'

This seems contradictory to me. Surely this warning should apply only to X2 caps and not Y2, as the latter are designed to fail open?

Has anyone come across this before?

Cheers

Liam
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Old 19th Jul 2017, 1:52 pm   #2
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Default Re: Y2 rated capacitor question

I agree, the warning refers to class X caps not class Y.
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Old 19th Jul 2017, 1:57 pm   #3
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Default Re: Y2 rated capacitor question

I just remember "X is a cross" ie across the mains.
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Old 19th Jul 2017, 2:05 pm   #4
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Default Re: Y2 rated capacitor question

The warning could be a mistake, or it could be the catch-all equivalent of 'may contain nuts'.
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Old 19th Jul 2017, 3:14 pm   #5
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Default Re: Y2 rated capacitor question

Get the data sheet of the capacitor from RS (they are good at that) and have a read.
 
Old 19th Jul 2017, 6:22 pm   #6
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Default Re: Y2 rated capacitor question

Some the Y2 caps I could find in RS were from the same generic range of Panasonic capacitors whose classification was X2 or Y2 depending on capacitance. Presumably bigger caps reactance is too low to limit normal operating leakage current to a safe value.

Another type http://uk.rs-online.com/web/p/polypr...itors/8752248/ for example has that warning but also says explicitly:

"KEMET R41 Series are metallized polypropylene Film Capacitors that have self-healing properties. Those polypropylene capacitors are used as interference suppressors for across-the-line applications and are suitable for use where failure of the capacitor could lead to danger of electric shock."

I guess the RS disclaimer

"Warning

Capacitors are designed for connecting directly across a mains supply but should NOT be used in positions where failure of a capacitor would expose anybody to electric shock."

Was slapped on all suppression caps willy nilly by a non technical catalogue compiler.


I've just had first hand experience of poor catalogue descriptions- a bunch of 2mm plug test leads delivered which were clearly described in the catalogue as 4mm plug test leads.
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Last edited by Herald1360; 19th Jul 2017 at 6:30 pm.
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