Mike, et al, Thanx for mentioning my name; by now you should be able to
tell the stories as we’ve talked thru these things before.
From my experience, protection is primarily needed for cord and
plug connected equipment where the earthing/grounding is not considered
reliable – which includes North America. Most such equipment is allowed to
have higher touch current under fault conditions, where the fault current
exceeds 5ma the GFCI provides the needed protection
Since GFCIs look for the ‘lost to ground current’, the
differential current in the power cord, they also work in circumstances where
the earth/ground doesn’t exist (a 2-wire installation) or where it should
exist but doesn’t. Many are installed in older 2-wire installations because of
this in the USA.
RCDs rated to trip at 30mA are working right at the c1
Ventricular Fibrillation level of IEC 60479-1 so should provide that protection
for most people.
Not sure if RCDs are tested or rated for catching performance
degradation in machines but you apparently have experience with that. It would
be nice to see a paper on that performance feature.
North American GFCIs are rated at 5mA which is the
letgo-immobilization limit specified in IEC 60479-1. (Yes, I know the
allowable range is not trip at 4mA but must trip at 6mA; the rated trip current
is still 5mA.) You can still disengage from the current at that level,
providing that level of protection.
Both North American GFCIs and Euro RCDs are not rated to deal
well with high frequency signals generated by Switch Mode Power Supplies and
Variable Speed Drives for motors. Lots of ‘nuisance tripping’ results. There
is an ongoing UL project to get a handle on this and get it fixed here in NA.
Yes, EV chargers are being provided with GFCIs at higher levels,
depending upon the installation/application parameters.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 1067
Albany, ORe 97321-0413
503/452-1201
IEEE Life Fellow
IEEE PSES 2020 Distinguished Lecturer
<http://www.researchgate.net/Peter%20Perkins> www.researchgate.net search my
name
<mailto:[email protected]> [email protected]
Entropy ain’t what it used to be
From: MIKE SHERMAN <[email protected]>
Sent: Thursday, February 3, 2022 12:48 PM
To: [email protected]
Subject: Re: [PSES] Machinery Leakage Current
Doug --
Thanks for mentioning this!
Yes, I've seen these 30 mA RCDs or RCCBs before, but not an RCBO (confused?
Google can explain these acronyms).
I've even recommended these for large machinery. The ones we used had
adjustable trip points up to 30 mA. Note that I recommended these for MACHINE
protection, not PERSONAL protection. The theory was to monitor potential
breakdown of the dielectric of the machine by watching the ground leakage
current. As I recall, early on we found, before it failed completely, a
variable speed fan drive motor with bridged dielectric that was grounding out
through a shaft bearing.
I'd love to hear what PETE PERKINS has to say about this!
Personally, given that North American GFCIs for 120 VAC have trip points of 4-6
mA, I've tended to not like to exceed that number. As I recall, Pete has
demonstrated that even 5 mA will be a current to remember if you conduct it.
That said, I think Pete told me a while back that the NEC is raising the
allowable leakage current for EV chargers to something quite above 5 mA. I'm
sure there's a good story behind that.
Note also that GFCIs, and as I recall the RCD we were using, could fail
silently and thus needed to be tested regularly to ensure continued protection.
Mike Sherman
On 02/03/2022 8:23 AM Doug Nix <[email protected] <mailto:[email protected]> > wrote:
Hi Mark,
I’ve seen mains filters used for 400 V 3 ph. 200A services with leakage
currents close to 30 mA. Consider that RCBOs commonly used outside North
America have a design trip current of 30 mA, so leakage currents above 30 mA
will cause the RCBO to trip. None the less, these large leakage currents can be
startling the first time you see them “in the wild”.
Doug Nix
[email protected] <mailto:[email protected]>
+1 (519) 729-5704
On 1-Feb-22, at 13:24, Stultz, Mark
<[email protected]
<mailto:[email protected]> > wrote:
Hello,
Is there a hard limit for leakage current for machinery in the EU? IEC 60204-1
provides instructions in clause 8.2.8 for “equipment having earth leakage
currents higher than 10 mA”. This seems quite high so we have applied the 3.5
mA limits for class 1 stationary equipment in IEC 60335-1. Is there another
source for leakage current limits that is machinery-specific? There is nothing
in the type-C standard for this product type.
Thanks,
Mark Stultz
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