Remember that per the same section in D.2.2 Interpolation of Clearance is
only permissible for a part which has no direct connection to the mains supply,
etc.
Creepage Distance shall always be at least as large as the value specified for
Clearance. ( Therefore if you are mains connected you must default to the 1.5mm
value for 300V).
Steve Costello
National Instruments
______________________________ Reply Separator _________________________________
Subject: Re: CREEPAGE DISTANCE
Author: "Ray Russell" <[email protected]> at Internet
List-Post: [email protected]
Date: 11/6/96 8:49 AM
Hello Dick,
I agree that K.3 does not apply to the main circuits. Also, in my
experience, we had an industrial computer that used surge suppressers.
The agencies allowed us to perform the Hipot test prior to putting in
the surge suppressers and putting the cover on.
Also, under D.2.2 (for working voltages under 1000 V) there's is a
statement that permits interpolation.
Good luck,
Ray Russell
[email protected]
______________________________ Reply Separator _________________________________
Subject: CREEPAGE DISTANCE
Author: Dick Kool <[email protected]> at Internet
List-Post: [email protected]
Date: 11/5/96 6:59 PM
As an electronic designer for laboratory devices, our designs have to
comply with the IEC 1010 safety standard.
At this moment I have a few questions about this topic.
- Routine tests
For EMC purposes we use 275 V varistors between fase-earth and
neutral-fase. According to annex K.2 of amendement 2, a test voltage
of about 2000 Vdc must be applied between the mains terminals
connected together (fase and neutral) on one side, and all
accessible conductive parts (earth) connected together on the other.
No breakdown or repeated flashover shall occur. It's clear that
breakdown will occur.
In annex K.3 it's noticed that if voltage limiting devices are used,
the applied voltage may be less. But this exeption does apply for
the mains test of annex K.2 to my opinion. Is this correct?
- Interpolation of CREEPAGE DISTANCE
Annex D.3 of IEC 1010 states that interpolation of CREEPAGE DISTANCE
is permissible in accordance with IEC 664 table IV.
As I'm not in the possession of this standard, I would like to know
if this is a liniar interpolation. I will give an example.
The working voltage is 240 Vac, basic insulation is required,
pollution degree 2, and installation (overvoltage) category II. The
CREEPAGE DISTANCE is determined in Table D.4.
Working voltage CREEPAGE distance on printed wiring board
150V 0.5
300V 1.5
Distance = (Working voltage / 150) - 0.5
For 240 V the CREEPAGE DISTANCE will be 1.1 mm. Is this correct?
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From: "Ray Russell" <[email protected]>
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