PCB - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: October 14, 2014, 09:19:10 am
content: how wide does a PCB track need to be to carry 250V ac 13A

author: Simon
author_rank: Unknown
timestamp: October 14, 2014, 09:37:51 am
content: Download "saturn pcb tool" and play around with putting different numbers in to your hearts content.

author: con-f-use
author_rank: Unknown
timestamp: October 14, 2014, 09:50:07 am
content: Depends on the allowed temperature rise of your board, the allowed voltage trop, its thermal resistance, the thickness of the copper layer and the length and isolation of the track.Should be about 10mm for 1oz copper.

author: Simon
author_rank: Unknown
timestamp: October 14, 2014, 10:10:44 am
content: 2oz is easily available and should definitely be considered.

author: geggi1
author_rank: Frequent Contributor
timestamp: October 14, 2014, 11:44:24 am
content: One way to have higher current capacaty on narrow PCb track is to put on ekstra solder. It is done comercialy on a lot of products.

author: Simon
author_rank: Unknown
timestamp: October 14, 2014, 12:19:11 pm
content: yes, usually referred to as plating and it's not done with solder, it's a way of starting with one thickness and building it up. Bear in mind solder is 1/10 the conductivity of copper so every 1mm of solder is like 3oz of copper (105um)

author: Unknown
author_rank: Unknown
timestamp: October 14, 2014, 12:22:49 pm
content: I saw one of Dave's videos about this a while ago. Solder plating traces ro reduce resistance. As I remember it did make quite a difference.EDIT: It may have been one of Mike's videos actually. I can't find it now.EDIT2: Found it:

author: Simon
author_rank: Unknown
timestamp: October 14, 2014, 12:25:35 pm
content: Yes you can add solder and it will help a lot because you can easily add 2mm of solder so that is like 6oz that is quite heavy.

author: Wilksey
author_rank: Super Contributor
timestamp: October 14, 2014, 12:52:28 pm
content: Couple of things.1) Mains is DANGEROUS!Ok, now that's out of the way.2) Do you really need 13A? A lot of plugs are not actually fitted with a 13A fuse, they are just commonly referred to as a "13A plug", for example, look on your laptop power supply, it might supply something like 19V @ 4.3A on the DC side, but AC will be 230-250V @ 0.6A or something, so you could get away with 2A which is <1mm.3) If you are using a AC to DC converter on a PCB, don't forget isolation slots!4) Not necessity, but I always put a PCB fuse or panel mount fuse to the equipment as if that does short out things can get a bit toasty!If you do require 13A, then go with 10mm traces as a MINIMUM I would say for 1oz copper, I would plate the traces as people have said here, or use 2oz copper.

author: con-f-use
author_rank: Unknown
timestamp: October 14, 2014, 01:26:55 pm
content: Quote from: Wilksey on October 14, 2014, 12:52:28 pmVery good point.Always(!!!) use a fuse unless you like fires around your projects. It will not save your project but might save your life.Okay and just for completeness: 250V need clearance. Keep every other trace well away from that.

author: Unknown
author_rank: Unknown
timestamp: October 14, 2014, 04:13:57 pm
content: Quote from: con-f-use on October 14, 2014, 01:26:55 pmWould routing a physical gap in the board around those traces be a way to go?

author: con-f-use
author_rank: Unknown
timestamp: October 14, 2014, 04:26:43 pm
content: Letthat. Here is acreepage/clearance calculator. For most PCBs 5mm between the tacks should be fine without routing. Routing makes the creepage distance ?.

author: Wilksey
author_rank: Super Contributor
timestamp: October 14, 2014, 04:31:28 pm
content: At 250V peak, I would suggest a clearance of around 2mm - 2.5mm between traces (IPC-2221B Calculations).If the mains is going into a transformer for example, I would get a decent gap milled between the HV and LV of the transformer, something a spark will not be able to jump across.The bigger the better / safer.

author: Monkeh
author_rank: Super Contributor
timestamp: October 14, 2014, 04:35:36 pm
content: Quote from: abdullahseba on October 14, 2014, 09:19:10 amPlease think very carefully about what you're doing and why. If you're asking such simple questions, working with mains may not be advisable.Quote from: Wilksey on October 14, 2014, 04:31:28 pm350V peak...

author: Wilksey
author_rank: Super Contributor
timestamp: October 14, 2014, 05:04:27 pm
content: Why 350V peak?

author: Monkeh
author_rank: Super Contributor
timestamp: October 14, 2014, 05:07:16 pm
content: Quote from: Wilksey on October 14, 2014, 05:04:27 pm250V RMS, ~350V peak, ~700V peak-to-peak.

author: Wilksey
author_rank: Super Contributor
timestamp: October 14, 2014, 05:25:58 pm
content: Duh,Sorry, not with it today!1.4 x VRMS is peak, of course.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 15, 2014, 01:51:41 am
content: Quote from: Wilksey on October 14, 2014, 05:04:27 pmBecause the original question said 250 VAC. Since it has no qualifiers, it's assumed to be RMS. 250 * 1.414 is pretty close to 350.