What is the formula for three-phase motor amps?

I = (HP × 746) ÷ (1.732 × V × efficiency × power factor). A 10 hp, 460 V motor at 90% efficiency and 0.85 PF draws about 12 A.

Should I size overloads on nameplate FLA or the NEC table?

Overload protection is set from the motor nameplate FLA; the NEC table values are used for conductor and branch-circuit sizing.

More than about 10% current imbalance between legs usually points to supply voltage imbalance, a loose connection, or a shorted winding.

Formula

I = (HP × 746) / (√3 × V × η × PF)

Phase

Power unit

Motor power

Voltage

Efficiency (η)

Power factor

Full Load Amps

12.24A

10.00 HP ≈ 7.46 kW · verify against nameplate.

Overload setting (115%)

14.08A

NEC max 125% = 15.30 A

Delta winding current

7.07A

Use this for wye-delta heater sizing.

Compute single- and three-phase motor current from horsepower, voltage, efficiency and power factor.

What is the formula for three-phase motor amps?: I = (HP × 746) ÷ (1.732 × V × efficiency × power factor). A 10 hp, 460 V motor at 90% efficiency and 0.85 PF draws about 12 A.
Should I size overloads on nameplate FLA or the NEC table?: Overload protection is set from the motor nameplate FLA; the NEC table values are used for conductor and branch-circuit sizing.
What does high amp draw on one leg mean?: More than about 10% current imbalance between legs usually points to supply voltage imbalance, a loose connection, or a shorted winding.