Ping Terry Given. PCB trace widths on motor drive.

Yep, that sounds about right for the traditional calculations based on the original IPC "warm and fuzzy" graphs. These "correct" calculations are based on old and incomplete empirical data, so take'em with a grain of salt. In relality you can often get away with less than this for track width, but it depends on your application and what you can tolerate in track losses. You can get your tracks tin plated to decrease the resistance, that helps a *lot*. If however you are using solder mask over bare copper then you have to be more careful. Specifying 2oz copper is a wise move and common practice for power stuff.

Personally I'd use more than 103mil for the spacing, just to be on the safe side.

You can't really find that kind of info, it's just "do the best you can". Using a thicker copper, tin plating, and using parallel traces on both sides of the PCB (even multi layers too) are the tricks used, and keep your necking as short as possible.

IPC-2221 has general clearances listed, but not for equipment classes.

always use a lot more than that if you can.

Hope that helps.

Dave :)

Cheers for that dave. I just need someone to double check my maths. I am using a fairly old copy (circa 5 years ago) copy of IPC standards, and half the books are missing :)

I guess the next challeng is how to maximise clearance when there is no room.

BTW: Roughly, what sort of percentage cost increase would one expect these days by moving from 1oz to 2oz copper?

Yep, your calcs work out perfectly based on the IPC data.

In this case you can use a routed slot between the tracks, that helps a lot. Although if the routing slot is small you might pay a premium for it from the manufacturer. They complain they break lots of bits this way, like it's *our* fault ;-)

Not much, around 5-10% is a ballpark figure. Does vary a lot between manufacturers of course. If you want high volume it pays to shop around.

Dave :)

Hi Guys,

I cant post to ABSE as my ISP doesnt support it :(

but I do have a PDF of the relevant graphs. email me, and I'll send it back.

0.56" is slightly off the curve, but comes in at around 12A for a 10K dT. 0.2" will have a 20K dT at a bit over 10A.

as far as necking down to pins etc - think in terms of heatsinking. a very short & skinny trace can carry a substantial current as long as both ends are well heat-sunk, ie connected to a ruddy great lump of Cu.

0.103" is a bit small for creepage and clearance. the amount required is a function of what it achieves, and the standards you are required to meet. Most standards dont actually care about "working" insulation, only safety stuff - IOW they dont care if the gear blows up. This also explains how one can use T0-220 parts with legs very, very close together.

I'd go for >= 3.2mm if I could. think condensation etc.

Cheers Terry

Cheers for that. My email is a dot pearson at tpg dot com dot au