Hello David! For currents if that magnitude nobody seems to think about IGBTs. They are quite OK, even for high voltages and switching frequencies up ~20kHz AFAIK. Best regards, Michael Nagel -----Original Message----- From: David Cary [mailto:[log in to unmask]] Sent: Donnerstag, 26. Juli 2001 23:18 To: [log in to unmask] Subject: [DC] high-current relay Dear Designer Council, I'm working on a project where I need to switch a little over 60 A of current. I know I could just put lots of MOSFET transistors in parallel, and they will share the current. Just like light bulbs in parallel, if one is getting more than its share, it heats up, *increases* resistance, which redirects more corrent to the other items. It looks like mechanical relays are much cheaper, although they are only rated up to 40 A (something about UL rating ?). If I just put 2 relays in parallel to switch that 60 A, will they share the current properly (like MOSFETs) ? Is there any tech notes talking about putting relays in parallel ? I didn't find any at http://siemens.com/ http://www.azettler.com/ http://www.pandbrelays.com/ . I hear that if I put lots of (BJT) npn transistors in parallel, when one gets more than its share, it heats up, *decreases* in resistance, then the positive feedback (``thermal run-away'') makes that transistor blow up, soon followed by its neighbors. That doesn't happen with relays, does it ? -- David Cary ---------------------------------------------------------------------------- ----- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------