In this guide, we break down how to find the Full Load Amps (FLA) for different motor types—single-phase, three-phase, and DC—using NEC tables and adjusting for voltage or power factor when needed. You’ll learn how to read the right columns, apply the correct multipliers, and avoid common pitfalls like missing footnotes.
When you're diving into motor calculations, the golden rule is: Start with the FLA (Full Load Amps).
Single-Phase Motors (Table 45)
Most of the time, you’ll see voltages like 115V or 230V. If your question throws a different voltage at you (like 208V), don't panic — check the NOTES under the table. They’ll tell you what multiplier to use.
Example:
Motor: 1ø, 5HP, 208V
Table 45 says: 28A
Note 1 tells us: Add 10% for 208V
So: 28A×1.10 = 30.8A ← That’s the FLA you’ll use!
Three-Phase Motors (Table 44)
Squirrel Cage, Wound Rotor Motor, Synchronous
Pay close attention! You need the right voltage column AND the right motor type. Also, don’t forget to read the Notes—Power Factor (PF) might throw a multiplier at you.
Example:
Motor: 3ø, 60HP Synchronous, 575V, 80% PF
Table 44 says: 51A
Note 3 says: Multiply by 1.1 for 80% PF
So: 51A × 1.1 = 60.5A ← That’s your new FLA!
Final Tip!
If the motor has a Nameplate — go with what it says! If not, grab those tables and get calculating.