I agree, and in fact the presence of an insulation resistance
(IR)requirement in safety standards is a menace. Typically, the
requirement is 'not less than 2 Mohms' . Now the IR of a typical piece
of new equipment is around 100 Mohms, or even very much higher. If that
has degraded to 2 Mohms, the insulation concerned is deep in failure
mode and may not last the week.
I have pointed this out in the past, but it didn't have any effect.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2018-08-14 17:59, Richard Nute wrote:
Hi Ken:
Insulation resistance test and hi-pot test are two distinctly different
tests.
Insulation test (measurement) must be done with dc and is to measure the
resistance of the solid insulation. The insulation resistance meter is a
high-resistance ohmmeter; as such it needs a high-voltage source, commonly
500 or 1000 volts, and sometimes more.
Hi-pot test can be either ac or dc and is to establish the minimum electric
strength of both the solid insulation and the air insulation (clearance).
As I said before, the traditional hi-pot test voltage is twice rated voltage
plus 1000.
If your client/customer specifies insulation resistance, then the
measurement is the resistance of the solid insulation. In my opinion, this
measurement excludes the solid insulation of capacitors. And, the
capacitors will slow the measurement as the source resistance of the
insulation resistance tester charges the capacitors.
Insulation resistance measurements are common to power distribution, but no
longer common to utilization equipment. This is because modern insulations
are no longer hygroscopic (and have few other degrading effects) and are
quite good compared to older designs.
I suggest you need to clarify whether the test is insulation resistance or
electric strength. And thanks to Pat Lawler for pointing out that Ken's
original post was in regard of insulation resistance.
Best regards,
Rich
-----Original Message-----
From: Ken Javor <ken.ja...@emccompliance.com>
Sent: Tuesday, August 14, 2018 7:37 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] X & Y Cap rating due to hipot test
No one knows about the eeseal. It's a possible EMI fix. I don't know were
the 1000 V hipot test came from; I supposed it was insulation
resistance/creepage-based. The point is, it is a dc requirement and the
device will never see 1000 Vdc elsewhere, therefore it seems like an
inappropriate requirement to place on a cap as a WVDC rating, and I don't
see why it should be placed on an EMI filter external to the EUT.
Ken Javor
Phone: (256) 650-5261
From: Pat Lawler <plawl...@gmail.com>
Reply-To: Pat Lawler <plawl...@gmail.com>
Date: Tue, 14 Aug 2018 07:07:42 -0700
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] X & Y Cap rating due to hipot test
Hi Ken,
In your original post, you mentioned this was a '1000 V insulation
resistance test'.
When I hear about insulation resistance testing, I think about leakage
currents. For this reason, I think the eeseal capacitor assembly
should be installed during test.
I don't know why the test level is 1000 V. Maybe the spec writer
simply chose the most stringent Test Condition in MIL-STD-202-302
(Level C) because it looked good. If the customer knew about the
eeseal parts during writing of the product spec, maybe they saw a
'1000 V' rating somewhere in the component spec, and simply copied it.
Pat Lawler
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