Motor Short Circuit Current Rating

Mr. Pickle

Member
Location
Rogers MN
Occupation
Electrical
NEC requires SCCR ratings for control panel, motor controls, etc.
NEC also requires a suitable KAIC rating for distribution equipment.

As far as I can tell NEC, doesn't address the KAIC or SCCR value for motors themselves.

Why don't motors have a KAIC value?
Is there a typical KAIC vaule for motors?
Why doesn't the NEC address this?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Engineer
AIC stands for Amps Interrupting Capacity, it only applies to overcurrent protective devices that break fault currents (i.e. fuses and breakers). The applicable code section is 110.09.

SCCR stands for Short circuit Current Rating and is applicable to all devices that do not breaker fault current, but rather need to tolerate the fault current until a protective device operates. The applicable code section is 110.10.

Motors, themselves, do not need to withstand fault currents so they would not need to have an SCCR. Motor controllers do need to have an SCCR.
 

petersonra

Senior Member
110.10 Circuit Impedance, Short-Circuit Current Ratings, and
Other Characteristics. The overcurrent protective devices, the
total impedance, the equipment short-circuit current ratings,
and other characteristics of the circuit to be protected shall be
selected and coordinated to permit the circuit protective devices
used to clear a fault to do so without extensive damage to
the electrical equipment of the circuit. This fault shall be
assumed to be either between two or more of the circuit
conductors or between any circuit conductor and the equipment
grounding conductor(s) permitted in 250.118. Listed
equipment applied in accordance with their listing shall be
considered to meet the requirements of this section.
The motor would be downstream of the circuit conductors so is not an issue when considering a SCCR>
 
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