Re: [PSES] High Touch Current in Industrial Machinery

[Douglas Powell]

Brian,

You can try a low leakage 3-phase EMI filter design.  This is where your
magnetic stage(s) are unchanged and three existing large Y-caps are tied
together to form a wye configuration between phases; the center tie point
of the wye is not directly earthed. Instead, use a fourth Y-cap tied
between this central node and earth. I think of this point as an artificial
neutral.

In essence you can make the three large caps nearly as large as you like,
just be sure they're all the same value and the voltages will nearly cancel
with respect to earth, give or take a few volts based on a slight mismatch
of the three. And the leakage current to earth through cap #4 should be
very small.  Play around with the value of that fourth cap to optimize RF
common mode emissions and simultaneously keep line frequency leakage
current low.

BTW, VFDs are one of the worst to deal with for EMC.

Good luck, Doug


Douglas E Powell
970-646-3732 (m)
Laporte, Colorado USA

On Fri, Feb 16, 2024, 2:24 PM Brian Kunde  wrote:

> I am working on an Industrial Machine with a 3-phase 5hp motor driven by a
> VFD. To pass the EMC conducted emissions requirements, we had to add a RF
> Line Filter that is recommended by the VFD manufacturer.  This filter has
> large Y-Caps. I know these currents theoretically cancel out in a balanced
> system, but when performing the traditional Touch Current test according to
> IEC 60990 6.2.2.2, Fault Condition No. 1 (open Protective Conductor) we
> measure a current about 50mA.
>
> However, the standard says that "this subclause do not apply to reliably
> earthed equipment. . . .". This Industrial Machine is either permanently
> wired or it can use an industrial grade plug and socket, so this fault test
> would not apply.
>
> So even though the measured current is high if we perform this fault test,
> because the machine is well grounded I do not have to do anything?
>
> In contrast, the IEC 62368 would require a warning label, warning in the
> manual, and a secondary PE terminal.
>
> I have read comments online such as, "in the industrial environment, they
> don't give a hoot about leakage current." Is this true?
>
> On the other hand, an industrial machine could be the size of a building
> and have dozens of VFD driven motors and line filters creating a huge
> amounts of currents in an unbalance environment. So in my case, do I have
> any concerns other than to insure the machine is well bonded to PE during
> installation? But isn't this a normal installation consideration?
>
> Thanks to all.
> The Other Brian
> --
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Re: [PSES] High Touch Current in Industrial Machinery

[Stultz, Mark]

Hi Brian,
Since this is machinery, typically IEC 60204-1 would be applied.  Check out 
clause 8.2.6 Additional requirements for electrical equipment having earth 
leakage currents higher than 10 mA.

Best regards,

Mark Stultz | CMSE(r) | Sealed Air | AUTOBAG(r) brand Equipment | Streetsboro, 
OH | 330-342-2402

From: Brian Kunde 
Sent: Friday, February 16, 2024 4:24 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] High Touch Current in Industrial Machinery

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I am working on an Industrial Machine with a 3-phase 5hp motor driven by a VFD. 
To pass the EMC conducted emissions requirements, we had to add a RF Line 
Filter that is recommended by the VFD manufacturer.  This filter has large 
Y-Caps. I know these currents theoretically cancel out in a balanced system, 
but when performing the traditional Touch Current test according to IEC 60990 
6.2.2.2, Fault Condition No. 1 (open Protective Conductor) we measure a current 
about 50mA.

However, the standard says that "this subclause do not apply to reliably 
earthed equipment. . . .". This Industrial Machine is either permanently wired 
or it can use an industrial grade plug and socket, so this fault test would not 
apply.

So even though the measured current is high if we perform this fault test, 
because the machine is well grounded I do not have to do anything?

In contrast, the IEC 62368 would require a warning label, warning in the 
manual, and a secondary PE terminal.

I have read comments online such as, "in the industrial environment, they don't 
give a hoot about leakage current." Is this true?

On the other hand, an industrial machine could be the size of a building and 
have dozens of VFD driven motors and line filters creating a huge amounts of 
currents in an unbalance environment. So in my case, do I have any concerns 
other than to insure the machine is well bonded to PE during installation? But 
isn't this a normal installation consideration?

Thanks to all.
The Other Brian


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[PSES] High Touch Current in Industrial Machinery

[Brian Kunde]

I am working on an Industrial Machine with a 3-phase 5hp motor driven by a
VFD. To pass the EMC conducted emissions requirements, we had to add a RF
Line Filter that is recommended by the VFD manufacturer.  This filter has
large Y-Caps. I know these currents theoretically cancel out in a balanced
system, but when performing the traditional Touch Current test according to
IEC 60990 6.2.2.2, Fault Condition No. 1 (open Protective Conductor) we
measure a current about 50mA.

However, the standard says that "this subclause do not apply to reliably
earthed equipment. . . .". This Industrial Machine is either permanently
wired or it can use an industrial grade plug and socket, so this fault test
would not apply.

So even though the measured current is high if we perform this fault test,
because the machine is well grounded I do not have to do anything?

In contrast, the IEC 62368 would require a warning label, warning in the
manual, and a secondary PE terminal.

I have read comments online such as, "in the industrial environment, they
don't give a hoot about leakage current." Is this true?

On the other hand, an industrial machine could be the size of a building
and have dozens of VFD driven motors and line filters creating a huge
amounts of currents in an unbalance environment. So in my case, do I have
any concerns other than to insure the machine is well bonded to PE during
installation? But isn't this a normal installation consideration?

Thanks to all.
The Other Brian

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