Question

What are the differences between the uses of MSPs in USA versus their uses internationally?

Answer

„h MSP¡¦s USA
o Does not meet UL 489
o Cannot be used for stand alone short circuit breaking
o Can be used as ¡§group motor rating¡¨ (UL/CSA)
o NEC 430-53 (sizing guidelines)
o Indicates that a single short circuit protective device can protect several branch circuits.
o If the short circuit current exceeds the withstand rating of the MSP then fuses must be used in series to protect the circuit or the system must be redesigned to accommodate (NEC 110-10).
„h MSP¡¦s international
o IEC 947-4-1
o Recognized as a stand-alone short circuit protecting device.
o Back-up fuses are only required when the fault current exceeds breaking capacity of the MSP.

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FAQ Subcategory: None

This item was last updated on 2004-02-18
Document ID: 857

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