OT: Short Circuit Current Calculation To Satisfy EN60204

[Manglemender]

Keith,

If you are installing in France ypu ned to check what type of power/earthing system will be used to supply the machine. IT supply is quite common in france; this is where star point of the transformer is not earthed. http://en.wikipedia.org/wiki/Earthing_system#IT_network

A single fault to earth/ground will not trip a breaker but will cause there to be a potential difference of line voltage between the other two phases and earth/ground. In an IT system you must detect this first fault. http://www.bender-us.com/knowledgebase/?a=ground-fault-detection-ungrounded-system

In addition you should be aware that many VFDs don't like IT systems and it is for this reason that one of my current projects being installed in France has a 500KVA isolation transformer.

Nick

 

[chud]

Sorry to chip in here Manglemender. But the drives I know you must just disconnect the earthing to the rfi filters on the drive to work with IT earthing. Or is there some othere reason i dont know about why you would supply them with an extra transformer?

 

[Manglemender]

Chud,

You are quite correct but some manufactures handle it better than others. Some are easy to alter, some have to be specifically ordered and some manufacturers put a get out clause in their manuals.

My current project in France is fitted with Bosch Rexroth servo drives but Bosch Rexroth wouldn't gaurantee the performance of the drives on an IT supply and suggest that a separate transformer is used to supply the drives with a TN-S system. It was easier to fit one large transformer for the whole machine rather than multiple smaller transformers in various panels down an 80M long production line.

Nick

 

[kamenges]

Thanks for the heads up, Nick. I will definitely check into that.

Keith

 

[kamenges]

I finally got around to getting the relevant standard and have begun a calculation of the Icc value. I does appear to be pretty straightforward.

The question I now have is related to the correction value "n" from Table 4. Is this used as part of the Icc calculation value or is it limited to determining Ipk or toher values? I am using a current-limiting fuse that would allow me to list a value of 35kA rms for Icc based on the peak let-through value of the fuse and the requirements of downstream components (I am using the value of Ics for the downstream components as opposed to the Icw value). However, if I need to use the correction value in Table 4 I need to limit the listed Icc to 17.5kA rms.
I am inclined to simply list 17.5kA as the Icc but I don't want to unduly burden my customer.

Any help would be appreciated.
Keith

 

[Sidewinder]

Please be aware that the 60439 series are in the process of being replaced.
60439-1 current UK status, current, superseded
60439-3 current UK status, current, revised
60439-5 current UK status, current, revised
All other parts are no longer current in the UK, and these parts have been replaced and are "on their way out".
I would expect the same situation throughout the EU TBH.

 

[kamenges]

What standard is it being replaced with? Or are the items listed as part of 60439 being sprinkled into other standards?

Keith

 

[Sidewinder]

The 60439 series is being replaced by the 61439 series, with updates and re-structuring.

 

[engineer.ashaban]

Dear all
I'm new at PLC programming , I hope that you can help me find a s7 300/400 ladder diagram real practical application books

 

[kamenges]

Thanks, Sidewinder. I'll make sure we stay on top of this and get the new standards when they come out. Do you know the approximate timeframe for this?

Keith

 

[Sidewinder]

Keith,
Try the link below, I hope:

http://shop.bsigroup.com/SearchResults/?q=61439&no=0&d=N)4294959469(Ne)1445&c=10&f=&t=r

This will give you an idea of the status of standards in the UK, you can search on all standards and check which is the current version even if you don't want to buy!

HTH


Paul