# VFD Safety Stop function



## Del (Feb 10, 2011)

Hi there Guys and Gals,

I thought I would let you know of a new function on drives that is starting to appear.

It is the Safety Stop function, enabled in european safety legislation. It is a means of stopping re-energisation of the drive IGBT diodes, on the output, after a stop. Its not an ESD or E-stop, but most of the new drives won't work without it.

We just had it fail on us on a site, and was not shown on the MCC drawings, but was in the drive manual, once we finally found one!

It's often a switched signal, or a link if not required, paired with a check back NC signal. 

I think that the drive manufacturers that target the european market will have this function- hence all the big boy drive players will have this now.

I thought this might help.

Regards

DEL

and for those of a certain wet place between the Atlantic, and the North Sea- Yes my dad is called Rodney- but thats another discussion altogether.


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## MDShunk (Jan 7, 2007)

Yeah, been doing this in the US for a couple years now. I'm mostly an Allen Bradley guy, so I use the Drive-Guard module. It's just a tiny little card that clips in the drive and you hook your two e-stop/process stop conductors on it and down to the drive's terminal strip. They have a similar product for the servo drives, but I don't know what it's called. I don't get in contact with servo drives, normally. Matter of fact, all of AB's MCC's and new MCC buckets are shipping with the DriveGuard module installed, I notice.


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## RSmike (Jul 31, 2008)

*great for servos*

The safe off function on the AB servos is a wonderful thing. No more lost home positions on power off. 

These devices are 'emergency stop' rated. So while they don't physically disconnect the power they put the drive in a 'recognized' safe and stopped state. Meaning people can put their fingers where they once couldn't when there is still power on the devices.

Plus it's a chance for the mfg to sell us something else that they mandated we needed.

RSlater,
RSmike


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