Peter, Y capacitors are usually required to limit RFI emissions from a power supply or other noise generating parts of the product. As you say, they are connected between the supply input and the earthing point of a class 1 product or between the supply input and accessible secondary circuits of a class II product. Because a failure of the Y capacitor will increase the risk of electric shock they are always required to be approved according to the appropriate standard. The fact that the product is of class 1 or class II protection; or is a class I product not connected to an earthing circuit is irreverent to the risk of electric shock in the event of capacitor failure. In a class II product two Y capacitors are used in series unless a single capacitor is provided meeting the requirement for reinforced insulation. In much of the world earthing is not required for every socket outlet and it is accepted to connect a class I product to an ungrounded socket outlet. If you read the capacitor requirements and leakage current limits in IEC 335 or 950 this should become clear to you. Y capacitors ordinarily have the approvals necessary for world wide acceptance and are available form many major manufacturers. They do cost a bit more, but you should never consider using an ordinary unapproved capacitor in this application. Best Regards, Lou Aiken, LaMer LLC 27109 Palmetto Drive Orange Beach, AL 36561 USA tel ++ 1 251 981 6786 fax ++ 1 251 981 3054 Cell ++ 1 251 979 4648
----- Original Message ----- From: [email protected] To: [email protected] Sent: Sunday, December 07, 2003 10:55 PM Subject: Y-caps in class II Hello all, I know that Y-capacitors connecting line to ground and neutral to ground in a class I product have to be approved to IEC 384-14 and must have the appropriate rating and certification, etc. However if a class I product is used in a country where there is no ground or reliable ground, then surely the Y-capacitors have no meaning and basically can be any capacitors and not just Y1 or Y2, etc. Am I correct in this assumption? If so, can anyone point me to a clause in the 950 or an article or some kind of proof that confirms my assumption please? thanks Peter
