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3VL tripping characteristic

8/17/2011 1:25 PM	Rate (0)
lojzek Posts: 2 Rating: (0)	Hello! In our factory we have many Siemens circuit breakers (especially WL and 3VL type). I have a problem in understanding the tripping curves (which were hard to find) for ETU. Problems are in the "L" part of the curves. I understand the tripping curve of the ETU25B, which has the constant time of 10s at 6x Ir. But what about the "L" part of the ETU10 (I think - see photo) mounted on the 3VL breakers?. As it has settings for Ir, and tr also. I don't understand, how the tr setting affects the slope of the curve in "L" section, if you set it between 2,5 - 30 at let's say Ir=1? Can anybody explain me this, and show me the way, where I can find the explanation, Thanks, Branko Attachment Slika 007.jpg (788 Downloads)
lojzek Posts: 2 Rating: (0)
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8/19/2011 12:34 PM	Rate (1)
Amey Talekar Member Joined: 7/7/2010 Last visit: 7/1/2013 Posts: 2 Rating: (1)	Hi Branko, The L protection in 3VL /3WL is overload protection which follows the IDMT (Inverse Definite Mean Time curve). The time delay tr is from 2.5 sec to 30sec which is usually used to have a time base discrimation with the downstream breakers set at the same value of Ir. The time delay with increasing values would only move the curve upwards ( coordinates of the slope calculation would change),however the slope of the curve remains constant. I have attached Simaris curves output for same 400A 3P MCCB with ETU10 release. The settingsare for tr=2.5sec & tr =30sec. You can use Simaris Curves output to get the actual behaviour of the power distribution products for various fault requirements. I hope this replies your query Regards Amey Attachment Simaris Curves for 3VL47401SB360AA0.pdf (1035 Downloads)

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8/22/2011 8:24 AM	Rate (0)
lojzek Posts: 2 Rating: (0)	Thanks Amey, the explanation and attached curve was exactly the thing I was searching for! Thanks again! Branko
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