Minnesota Chapter IAEI Q&A

submitted by Sam Sampson, IAEI

Q:

NEC Section 430.6 applies to ampacity and motor rating, and refers you to Tables 430.247, 248, 249 and 259 but there is no 277-volt column in any of them. How would you determine the full-load current of a 277-volt motor?

A:

430.6 addresses motors marked in amperes rather than horsepower but does not specifically address in-between voltage ratings. However, it is not unusual to find a situation where the voltages in columns in those the Tables do not include the specific motor voltage you need, such as 277-volts.

In those instances, you need to use the motor nameplate and any other information provided by the manufacturer to determine the full load current .Also note that Section 430.7 has the specific markings required for motors.