I have a trace width calculator on my web site at http://www.aracnet.com/~gpatrick in the "PCB Data" section. It is based on equations from IPCWorks 97 (McHardy/Gandhi, Hughes Aircraft TP SO6-2-1). There is already some slack in the calculations, but it depends on the nature of the surge as much as how much surge current you are handling. If you are worried about a surge that occurs infrequently, for very short periods you might be able to go with the calculated value. What I normally do is calculate width at the steady-state current at a 10 degree rise, calculate trace width at the surge current at a 60 degree rise, then decide how wide to make the trace based on the time the surge is expected to be present. I am planning on incorporating some "fusing current" calculations into the calculator when I get a spare moment. These are based on a presentation from Doug Brooks at PCB East 2000. -- George Patrick Tektronix, Inc. Central Engineering, M/S 39-512 P.O. Box 500 Beaverton, OR 97077-0001 Phone: 503-627-5272 Fax: 503-627-5587 -----Original Message----- From: Amira Mohammed [mailto:[log in to unmask]] Sent: Monday, February 26, 2001 01:39 To: [log in to unmask] Subject: Re: [DC] Trace width Dear Phil and Gary, Thank you for both of you You are right .When I've asked about this,I told that we want some safty factor for surge current , so should I calculate the trace width depending on the maximum current value may be take place due to surge current, or there is another way to calculate it? Thanks in advance Regards, Amira Mohamed PCB Designer IEP www.bahgat .com > ---------- > From: Gary Ferrari[SMTP:[log in to unmask]] > Reply To: DesignerCouncil E-Mail Forum.;[log in to unmask] > Sent: Monday, February 26, 2001 4:21 AM > To: [log in to unmask] > Subject: Re: [DC] Trace width > > Amira, > > I tend to agree with Phil on this one. The 5 amp current should be a > continuos value. Is there any possiblilty that you may be seeing a surge > current of a much larger value when you turn on the circuit? > > Regards, > > Gary Ferrari > Executive Director > IPC Designers Council > 860-350-9300 > Fax 413 771-5386 > [log in to unmask] > ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------------