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 Post subject: 5000 cal rating
PostPosted: Fri Jul 30, 2010 8:07 pm 
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at work we have a ab drive line up with about 5 PF 700 drives. They pull around 1500-2400 amps total. these drives have 480 feeding a breaker then thru a NRU that converts it to DC and that feeds the buss for the drives then back to ac that feeds the motors and they have a 5000 cal rating, they said it could not be any lower. they allow operators to turn the disconnects on /off on these drives with just cat 0 PPE, Is this safe or should there be some type of remote operation on the drive disconnects located outside of the AF boundary of 20 ft? What would be the correct way according to 70 E?


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PostPosted: Fri Jul 30, 2010 8:34 pm 
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One line

Here is the one line


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PostPosted: Fri Jul 30, 2010 9:27 pm 
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The arcing fault current less than 10kA makes it pretty clear that the fault is just clearing in a long long time. Are the trip settings in the upstream breaker loaded correctly in the software? Are you aware that you can apply a manual cutoff time (minimum 2s)?

Can the breaker settings be adjusted to something faster for the projected arcing current range while still maintaining coordination with downstream devices? if not, can the breaker be replaced with another breaker with more trip curve adjustment options or with fuses (as long as coordination is still achieved)?

5000 cal/cm2 can definitely be reduced in your case by orders of magnitude, even if for some reason (say, coordination) you have to get light and overcurrent sensors (e.g. ABB REA systems) that send a trip signal to the upstream breaker.


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PostPosted: Sun Aug 01, 2010 7:55 am 
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PICKWICKBUCKTAIL wrote:
at work we have a ab drive line up with about 5 PF 700 drives. They pull around 1500-2400 amps total. these drives have 480 feeding a breaker then thru a NRU that converts it to DC and that feeds the buss for the drives then back to ac that feeds the motors and they have a 5000 cal rating, they said it could not be any lower. they allow operators to turn the disconnects on /off on these drives with just cat 0 PPE, Is this safe or should there be some type of remote operation on the drive disconnects located outside of the AF boundary of 20 ft? What would be the correct way according to 70 E?


If you really have a 5000cal situation, you AFB should be more than 20 Feet. Something is not right. But there are remote wirless devices that will operate your disconnects.


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PostPosted: Sun Aug 01, 2010 9:21 am 
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typo

i left a zero out, a little over 200 ft


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PostPosted: Sun Aug 01, 2010 5:59 pm 
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PICKWICKBUCKTAIL wrote:
i left a zero out, a little over 200 ft


Makes more sense, still should be mitigated and/or use remote switching.


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PostPosted: Wed Aug 04, 2010 8:45 am 
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PICKWICKBUCKTAIL wrote:
at work we have a ab drive line up with about 5 PF 700 drives. They pull around 1500-2400 amps total. these drives have 480 feeding a breaker then thru a NRU that converts it to DC and that feeds the buss for the drives then back to ac that feeds the motors and they have a 5000 cal rating, they said it could not be any lower. they allow operators to turn the disconnects on /off on these drives with just cat 0 PPE, Is this safe or should there be some type of remote operation on the drive disconnects located outside of the AF boundary of 20 ft? What would be the correct way according to 70 E?



What type and rating are the fuses between buses 1330 and 1340? Is X29 a reactor and was it included in the survey? Are the two fuses independent of each other or are they mounted on the same fuse clip?


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