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?
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You must the dielectric strength test without the varistor between
L-PE. You must add a gas tube in line after the varistor.
The Varistor between L and N must after the fuse.
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- 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
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Linear Interpolation in the used sector.
Distance =((1,5-0,5)/ (300 - 150))*(Workingvoltage-150)+ 0.5
Distance= 1.1mm
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For 240 V the CREEPAGE DISTANCE will be 1.1 mm. Is this correct?
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mechanical engineering and environmental D - 87600 Kaufbeuren
simulation
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