Under NEC 430.37, how many phases must overload protection be provided for a 3-phase motor?

Under NEC 430.37, how many phases must overload protection be provided for a 3-phase motor?

• A. One
• B. Two
• C. Three
• D. None

Answer: (C)

Three-phase motors rely on all three windings to carry current and share heat. If overload protection exists on only one or two phases, a fault or excessive current on another phase can still cause overheating and damage to the motor. NEC 430.37 requires overload protection on each phase so that any overload condition interrupts power to all windings, preventing damage from an unbalanced or single-phase overload. That’s why the correct approach is protecting all three phases. Providing protection for only one or two phases, or none, would leave the motor vulnerable and noncompliant.

Three-phase motors rely on all three windings to carry current and share heat. If overload protection exists on only one or two phases, a fault or excessive current on another phase can still cause overheating and damage to the motor. NEC 430.37 requires overload protection on each phase so that any overload condition interrupts power to all windings, preventing damage from an unbalanced or single-phase overload. That’s why the correct approach is protecting all three phases. Providing protection for only one or two phases, or none, would leave the motor vulnerable and noncompliant.