Hi Raymond:
> 1. Earth continuity test
> As the class 1 is due to the additional earthing plate, how can I ignore
> the earth continuity test?
Class I is due to the adapter having an appliance
coupler with a PE terminal.
> Without this earthing plate, the unit is in fact a class 2 construction.
No.
If the unit has a PE terminal, then the unit is
Class I.
The unit may be Class II construction, but if it
has a PE terminal then it is a Class I product.
> Thus, I am a bit confused with such construction and should I follow the
> required safety tests for class 1 or class 2.
For the purposes of testing for compliance to a
safety standard, the test for Class I apply.
For the purposes of true safety, then the primary-
secondary insulation should be tested for Class II.
> I have another thought that actually, the earthing plate and the DC output
> plug earthing are functional earthing, not safety earthing, so electrical
> continuity test using multitester is sufficient and earth continuity test
> using low voltage and 25A current is not applicable.
Yes, the earthing plate and dc output earthing are
indeed functional earthing.
However, they are connected to the PE, which is
insulated from the mains be basic insulation. If
the basic insulation should fail, then the PE
becomes live. If the dc output is connected to the
PE, then the dc output will become live in the event
of a fault in basic insulation.
In a sealed unit, the only way to test the PE portion
is via the functional earthing plate and dc output
terminal. So, a 25-ampere current is required to be
applied between the dc functional earth terminal and
the PE terminal.
> 2. Hi-pot test
> The unit passes the hi-pot test at 3,000Vac if the grounding plate and the
> bridging capacitor are removed. If only the bridging capacitor is
> removed, the test voltage goes upto about 2,100Vac max. I note that there
> is breakdown around the grounding plate and the pcd side of mains female
> connector at the max. voltage.
If the unit fails the hi-pot test between the mains
and the grounding plate, then the insulation between
the mains and the grounding plate is basic insulation.
Therefore, the grounding plate (because it is connected
to an accessible part, i.e., the dc output terminal)
must be connected to the PE and must pass the 25-ampere
test.
> It seems once the production of the converter is completed, proper earth
> continuity test and hipot test are unable to be done at IQC of receiving
> warehouse. Any suggestion to do some extend of safety test without
> destruction of the finished goods is appreciated.
The construction you describe will easily pass the tests
for Class I construction, i.e., 1500-V hi-pot, and 25-
ampere earthing continuity.
Unfortunately, you cannot test the double insulation
between mains and the dc output.
Best regards,
Rich
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