Offline SMPS isolation creepage and clearance

The safety standards don't specify requirements for functional isolation, e.g. switcher drain-source.

EN/IEC 61010 dedication is "Safety requirements for electrical equipment for measurement, control, and laboratory use". Not sure if it applies to your equipment.

The basic standard has been last revised in 2010. There are smaller ammendments and corrections since then but no fundamental changes, e.g. redefinition of clearance and creepage distances.

The parameters for clearance and creepage distances are nominal voltage, overvoltage category (expected transient voltage) and pollution degree. In some situations also resistance to tracking (insulation CTI value).

cupoftea said:

Hi,
Does anyone have the copies of the standards EN60010 and EN62368, which detail the clearance and creepage distances for EU Offline SMPS's?
I believe they changed recently?.....pri-sec is now 8mm?
Also, within the primary side.....flyback drain to Primary ground is 1.5mm?
(Where flyback drain goes up to 700Vpk).

Why is IPC2221A a free download but EN60010 and EN62368 are not?

Click to expand...

uninsulated conductor voltage spacing

For working voltage isolation (non safety)

voltage peak or DC between 30V<=V<100V spacing should be 0.1 + Vpeak X 0.01
between V=>100V spacing should be 0.6 + Vpeak X 0.005

Thanks,
In the following...
The table advises 2.5mm+1mm=3.5mm for the 700vpk of a flyback drain.
Thats for the bare pad of the to220 drain, or the RCD clamp capacitor highest voltage pad..... to eg primary ground and its control circuitry. (bare pad to bare pad)

..sorry, i meant A6, 1.5mm + 1.5mm = 2.5mm.
And its the RMS voltage that you look at...and because its over 30khz, the present standards may not apply in a soon-to-come revision

cupoftea said:

Hi,
Does anyone have the copies of the standards EN60010 and EN62368, which detail the clearance and creepage distances for EU Offline SMPS's?

Click to expand...

Please stop using the forums to ask people to pirate standards for you.

cupoftea said:

Why is IPC2221A a free download but EN60010 and EN62368 are not?

Click to expand...

They're managed by different bodies, who each get to decide what to charge for access to their standards.

Also IPC-2221 is not a safety standard.

Also IPC-2221A isn't free of charge, see https://shop.ipc.org/ipc-2221/ipc-2221-standard-only/Revision-a/english

Thanks, this is interesting....

...it says
.....>>>>>QUOTE
Requirements for HV Spacing?
There is no absolute limit per-se’ on HV spacing. The
electronics industry has used TO-220 packages to 1600 V
for many years
<<<<<<UNQUOTE

Also it says...
>>>>QUOTE
If 320 mils (0.320 inches) is the spacing for an opto rated at 5 KV peak, then the allowable spacing must be 15.7 V per 1 mil (0.001 inch) (5000/320= 15.7 V) for creepage and clearance.2. Since a TO-220 has a 0.050 clearance, this equals 785 V (15.7 * 50). This seems to agree with the industry rule of thumb of around 800 volts.
>>>>>>UNQUOTE

...so they are hashing a guess at 618V/mm for functional spacing in SMPS....as you can see, they do not use any official safety docs for the 618V/mm thing

...more estimation is done here...

>>>QUOTE
How much spacing is needed in high voltage circuits and setups? The general guideline in common use is to allow 7,500 to 10,000 volts, dc per inch in air; or 7.5 to 10 volts per 0.001 inches. These voltages will typically be lower over the surface of a material due to surface contaminants, moisture and/or the nature of the material.
>>>>>>>UNQUOTE

....kind of......give or take the odd kilovolt or so , ...whatever.

It makes you realise that its overthinking it to look very deeply into spacing for eg rcd clamp voltage to primary ground in a offline flyback.

It's actually underthinking.

Answer one question -
What are the consequences of the insulation failing?

1. Fire, house burns down.
2. A little smoke, fuse pops.
3. Granny gets electrocuted.
3. Nothing because it won't happen, the official numbers are "way too large".

In your snubber, or other places- ask yourself what will happen.

As you know, the insulation's environment (pollution degree) is also part of official spacings. Moisture, dust, altitude, tracking are taken into consideration necessitating extra allowances. Do you agree?

UL standards have specified criteria for working insulation systems inside a product - as they don't want to see limited arching lead to fire.