air spacing for 100v

[carmusic]

Hi i have made a custom pcb board with screws on it, i was wondering what is the minimum air spacing between 2 metal parts to be legal, the voltage may reach 100V , i currently have 0.1inch spacing (between the screw and the heatsink), is it enough, do i need to put an isolator between them?

 

[Speakerguy]

I don't know about legal requirements, but it sounds fine to me. I have used 6.3kv capacitors that had a lead spacing of only 10mm (0.4").

 

[Roff]

Google is your friend. I searched for "pcb spacing vs voltage". I found this:
IPC-2221 PCB Trace Clearance

 

[carmusic]

thanx i already know spacing for pcb's but for general use what the minimum spacing between two metal parts ?

 

[eng1]

Google for 'creepage'. This site has an on-line calculator based on an IEC standard. The distance depends on the voltage (rms or dc), on the material and on the degree of pollution.
This site lists the pollution classes.
As far as the material is concerned, you may evaluate the worst case for creepage (goup III) and check if your circuit is ok. Of course you'll calculate the minimum creepage distance.

 

[carmusic]

thanx that's perfect!

 

[Ubergeek63]

EN 60601-1 (CE medical) at 150VDC or 125VAC:

between parts of opposite polarity: AIR - 1mm, CREEPAGE - 2mm
basic insulation from HV or HP to user: AIR - 1.6mm, CREEPAGE - 3mm
double insulation: AIR - 3.2mm, CREEPAGE - 6mm

You will be hard pressed to find it on the web since they want to at least sell you the spec for $100, and hopefully 3-5 specs at $100 each in your search for this tiny bit of information. I have it because we design to it.

Dan

 

[carmusic]

ok i wiil have about 2.5mm

 

[Hero999]

Note that this is the peak voltage, if it's 100VAC then you should treat it as 141V, not that it matters in this case.