Actions
Forum Thread Details
  • State Not Answered
  • Replies 2 replies
  • Subscribers 278 subscribers
  • Views 232 views
  • Users 0 members are here
Related
See a helpful answer?

Be sure to click 'more' and select 'suggest as answer'!

If you're the thread creator, be sure to click 'more' then 'Verify as Answer'!

Need X1 safety capacitor ?

lwathelet

Dear all,

 

We are designing ultra miniature power supplies. I have a question regarding safety capacitors. To be conform to EN60950, we should use X1 capacitors between phase and neutral on primary circuits.

My question is: Is it allowed to use non-certifed capacitors between phase and neutral behind a fuse ? The fuse will thus protect the capacitor in case of shorcut. In case of fire, the product envelop is already UL-V0 certified.

 

Thanks in advance,

 

Luc

 

PS: attached schematic

Attachments:
image
  • 0

    Luc,

     

    When you say phase and neutral, this is in reference to AC? If so, it is recommended to get certified components.

     

    One batch of untested caps may work, another batch may explode. Just because the enclosure in UL/fire certified doesn't mean you should cut corners inside the case.

     

    You could be sued for being more concerned with saving money than making a safe product. Keep that in mind.

     

    Cabe

  • 0 in reply to Catwell

    Hi Cabe,

    Thanks for your answer. It's a very interesting discussion we have here. We sure wish to make very safe products and we won't take any risk on that side. I was wondering about a capacitor placed behind a fuse because there is a decision relative to capacitors used in switch power supply behind a rectifier. In this particular case, we can use non-certified capacitors. I thought this could be a similar application in my case. We are designing powerline communication circuits, and this capacitor is used as a decoupling capacitor to transmit and receive signals on the lines. So it has AC voltage (phase) on one side and low voltage on the other side. (assumed to be neutral)

    In fact I've just re-read the EN-60950 decisions (Decision n°91/5).

    http://www.ul.com/global/documents/offerings/industries/hightech/informationtechnology/resources/EN_60950x_DECISIONS.pdf

    They are also talking about capacitors before rectifier or after a fuse, it should be X1 capacitor.

    "The use of a mains fuse, a mains filter or a

    varistor cannot be a method to reduce installation

    category."

    So as you advised, it is definitely not a good method for saving money !

     

    Best regards,

     

    Luc