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1 Phase Motors and Fault Calc's
2

1 Phase Motors and Fault Calc's

1 Phase Motors and Fault Calc's

(OP)
Hey All,

I didnt' think about it much, but IEEE red book does not give any guidance about the inclusion of single phase motors in fault calculations.  Am I missing something,...any reason for this?  

Mike

RE: 1 Phase Motors and Fault Calc's

Any contribution from a single-phase motor would be extremely small and short-lived.  In most industrical facilities, anything larger than 1/2hp would be three-phase.  Since most of these are 120V or 208V, any contribution beyond the transformer would have to be insignificant.   

I've always neglected single-phase motor contributions.  I think this is an allowed assumption per ANSI C37 procedures.  

RE: 1 Phase Motors and Fault Calc's

(OP)
Thanks again dpc,

Mike

RE: 1 Phase Motors and Fault Calc's

Several years back,  

Several factors contribute to make less critical the performance of SC for single phase motors:

- The power source is usualy a small transformr, producing small available SC.
- Cost of SC study was difficult to justify for small installation.
 - Single phase motors are relative small capacity typically up to 5 HP.

- At LV the cable impedance is relativelly high. Therefore the SC is damping rapidly to safe levels.
- The contribution to SC is relatively small.



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