Brian Use of X cap after bridge rectifier is not required. There exist OSM decision that clarifies this.
Y caps are required in complete primary circuit towards PE. I hope this helps. Best regards Boštjan Glavič SIQ Poslano iz Outlook za Android<https://aka.ms/AAb9ysg> ________________________________ Od: Richard Nute <ri...@ieee.org> Poslano: ponedeljek, 3. april 2023 20:57 Za: EMC-PSTC@LISTSERV.IEEE.ORG <EMC-PSTC@LISTSERV.IEEE.ORG> Zadeva: Re: [PSES] X-Caps after Diode Bridge CAUTION: This email originated from outside of our organisation. Do not click links or open attachments unless you recognise the sender and know the content is safe. Hi Brian: I found these explanations on the web: https://www.tecategroup.com/products/capacitors/ac-safety-capacitors.php X Capacitors: Also known as "across-the-line capacitors." Class X safety capacitors are used between the "live" wires carrying the incoming AC current. These capacitors are used in applications where failure of the capacitor will not lead to risk of electrical shock to the user. A capacitor failure in this position will usually cause a fuse or circuit breaker to open. Y Capacitors: Also known as "line-to-ground capacitors" (line bypass). Y capacitors are used in applications where failure of the capacitor could lead to the danger of electrical shock to the user, if the ground connection is lost. Filter caps are on the load (DC output) side of the rectifier. The pulse (charging) current through the capacitors returns to the rectifier, and then to the AC line. While one side of the filter caps is often connected to ground, very little pulse current returns to the AC line via the equipment PE wire. Because the filter caps are not directly across the line, they are not X capacitors. Failure of a filter cap is usually mitigated by a fuse in the AC line. For further information on X (and Y) caps, see IEC 60384-14. Hope this helps. Best regards, Rich From: Brian Kunde <bkundew...@gmail.com> Sent: Monday, April 3, 2023 9:24 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] X-Caps after Diode Bridge We use X2 caps in RF filters prior to the Diode Bridge. Do filter caps after the Diode Bridge (DC), but before the isolation transformer, have to be X2? How about filter caps to Chassis/PE after the Bridge? Do they have to be Y-caps? Thanks, The Other Brian PS: We typically buy power supplies, so I am not familiar with the downstream requirements. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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