Re: [PSES] **External**[PSES] Fwd: Emergency Stop Function

[David Nyffenegger]

Brian,



Depending on your requirement you may need a risk assessment to something
like ISO 12100 or ISO 13849-1.  From that would be determined the minimum
performance level of the safety control system.  A single contactor could
be used as the VFD manufacturer suggests. For higher performance levels two
contactors in series with monitoring of the contacts may be required.   But
the contactor is brute force and doesn’t allow for controlled shutdown as
you have noted.  A VFD with STO input is an easier and cleaner approach and
allows controlled shutdown providing the performance level of the STO is
adequate for your requirements.  There more books, white papers, and
seminars than you can imagine on this topic.  The OEMs of the safety
control system components are more than happy to share their view and
documentation on the subject.



Note that a fundamental general requirement for an E-STOP is that releasing
the E-STOP does not in itself restart any motion.  If you are dropping a
VFD with a contactor or STO it will probably not re-start when the E-STOP
is released.  But in other cases a safety controller may be appropriate to
use with the E-STOP and STO or contactors.


-Dave

On Thu, Mar 19, 2020 at 1:31 PM Jim Hulbert 
wrote:

> I think you need a VFD with Safe Torque Off (STO) function.
>
>
>
> Jim Hulbert
>
>
>
> *From:* Brian Kunde [mailto:bkundew...@gmail.com]
> *Sent:* Thursday, March 19, 2020 1:19 PM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* **External**[PSES] Fwd: Emergency Stop Function
>
>
>
>
>
> If any of you have a Case of Corrona, I hope it is the type that comes in
> bottles or cans.
>
>
>
> First, there is a guy in this group who I chatted with in the past who is
> like an expert in the E-Stop function.  He has a Blog or Website dedicated
> to this topic which I cannot currently find.  Can anyone help me get in
> contact with him?
>
>
>
> My area of need is with integrating the E-Stop function with a Variable
> Frequency Drive (inverter).  I have to meet the international requirements
> as well as the USA and Canadian requirements.
>
>
>
> What I have is 3-phase AC power, through a Contactor, to a VFD, which
> powers a 3-phase motor.  The VFD has the motor brake feature built in.
> Under a normal STOP command, the VFD engages the motor brake.  All is
> fine.
>
>
>
> The VFD manufacturer's documentation shows to connect the E-STOP to the
> motor Contactor which OPENs power to the VFD.  When the E-Stop is engaged,
> power to the VFD is shut down; the motor continues to spin for up to 30
> seconds or more before coming to a stop.  The motor Brake does not engage
> because it is a feature of the VFD which is powered down.  This makes no
> sense to me.
>
>
>
> The E-STOP is supposed to stop motion as quickly as possible without
> causing additional Risk (according to the MD and NFPA 79 cat.2).  So how is
> the E-Stop function supposed to work with a VFD?  How is this typically
> done?  Are we buying the wrong VFD?
>
>
>
> Thanks to all.
>
>
>
> The Other Brian
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
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> emc-p...@ieee.org>
>
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> 
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/
> 
> can be used for graphics (in well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> 
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe)
> 

Re: [PSES] **External**[PSES] Fwd: Emergency Stop Function

[Jim Hulbert]

I think you need a VFD with Safe Torque Off (STO) function.

Jim Hulbert

From: Brian Kunde [mailto:bkundew...@gmail.com]
Sent: Thursday, March 19, 2020 1:19 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: **External**[PSES] Fwd: Emergency Stop Function


If any of you have a Case of Corrona, I hope it is the type that comes in 
bottles or cans.

First, there is a guy in this group who I chatted with in the past who is like 
an expert in the E-Stop function.  He has a Blog or Website dedicated to this 
topic which I cannot currently find.  Can anyone help me get in contact with 
him?

My area of need is with integrating the E-Stop function with a Variable 
Frequency Drive (inverter).  I have to meet the international requirements as 
well as the USA and Canadian requirements.

What I have is 3-phase AC power, through a Contactor, to a VFD, which powers a 
3-phase motor.  The VFD has the motor brake feature built in. Under a normal 
STOP command, the VFD engages the motor brake.  All is fine.

The VFD manufacturer's documentation shows to connect the E-STOP to the motor 
Contactor which OPENs power to the VFD.  When the E-Stop is engaged, power to 
the VFD is shut down; the motor continues to spin for up to 30 seconds or more 
before coming to a stop.  The motor Brake does not engage because it is a 
feature of the VFD which is powered down.  This makes no sense to me.

The E-STOP is supposed to stop motion as quickly as possible without causing 
additional Risk (according to the MD and NFPA 79 cat.2).  So how is the E-Stop 
function supposed to work with a VFD?  How is this typically done?  Are we 
buying the wrong VFD?

Thanks to all.

The Other Brian
-


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