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MCCB KA selection

Created by: PISCEAN 2010 at: 11/19/2010 5:26 AM (27 Replies)

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11/19/2010 5:26 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello Experts, I ahve to select 3 pole MCCB at input side of a machine. My question is whether I should go for 25 KA capacity MCCB or 50 KA capacity MCCB?Can any one help me. Thanks in advance. DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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11/22/2010 10:59 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello everybody, 30 views so far but not a single reply. Is it so difficult? DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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11/26/2010 9:53 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello Experts, Ok I will put this in another way. While selecting MCCB which one should be prefered i.e. 25 KA capacity or 50 KA capacity. Regards, DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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12/2/2010 11:48 AM	Rate (0)
srrr-in Posts: 7 Rating: (0)	Dear Deep, MCCB selection is depends on the Fault level of your Busbar ( or IncomingTransformer KA fault level). Based on your Fault level you can select the MCCB. Regards, Srrr
srrr-in Posts: 7 Rating: (0)
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12/2/2010 11:51 AM	Rate (0)
srrr-in Posts: 7 Rating: (0)	Dear Deep, MCCB selection is depends on the Fault level of your Busbar ( or IncomingTransformer KA fault level). Based on your Fault level you can select the MCCB. Regards, Srrr
srrr-in Posts: 7 Rating: (0)
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12/5/2010 7:23 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello srrr-in, Thanks for your reply. But we have equipped with Distribution panel board system & in this case e.g. suppose connected load is 70 Kw 3 phase, 415 Volt, 50 Hz. Main supply protection SFU is 160 Amp capacity, aluminium bus bar capacity is 25 mm x 3 mm 1 no per line. In this case what capacity MCCB to be selected means 50 KA or 25 KA? & what are the selection creteria? Thanks in advance. DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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12/16/2010 1:14 PM	Rate (0)
srrr-in Posts: 7 Rating: (0)	Dear Deep, What is yourLT Transformer Fault Level???? Sridhar
srrr-in Posts: 7 Rating: (0)
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12/20/2010 1:30 PM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hi srrr-in, Where shall I get that information. Regards, DEEP
PISCEAN 2010 Posts: 8092 Rating: (884)
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2/11/2011 3:31 PM	Rate (0)
Sentronix Posts: 66 Rating: (4)	Hello Deep, As an example you could check the "Planning Manual - Planning with SIVACON S8, Flexible Low-Voltage Switchboard", available on http://support.automation.siemens.com/WW/view/en/20356391/133300. Chapter 8.10 provides a table showing short-circuit currents of three-phase distribution transformers. These are maximum values on the transformer output. The longer the cable way from the transformer to your panel the lower this value (impedance of the cable). Regards, Sentronix
Sentronix Posts: 66 Rating: (4)
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2/12/2011 7:56 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hi sentronix, thank you very much for your valuable information. From the table, existing transformer short circuit currentof transformer is 32,791 (tranformer rating is 1500 KVA) But agin my basic question is what capacity MCCB should I select 25 KAor 50 KA? & why? Thanks & regards, DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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