Practice Test Geeks(E2) E2 Commercial Electrical Inspector Practice Test
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Sizing and Protection of Motor Circuits Flashcards

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  1. Per NEC 430.32(A)(1), overload protection for a motor with a service factor of 1.15 or greater must be set to trip at no more than what percentage of the motor's FLA?

    Answer: 125% of FLA

    Motors with SF ≥ 1.15 or temperature rise ≤ 40°C require overload protection set to trip at no more than 125% of FLA per NEC 430.32(A)(1).

  2. For a motor with a service factor of 1.0 and a temperature rise exceeding 40°C, what is the maximum allowable overload trip setting per NEC 430.32(A)(1)?

    Answer: 115% of FLA

    Motors without SF ≥ 1.15 or temperature rise ≤ 40°C are limited to an overload trip setting of no more than 115% of FLA.

  3. A 460V, 3-phase motor has a nameplate FLA of 22A and a service factor of 1.15. What is the maximum overload relay trip setting per NEC 430.32(A)(1)?

    Answer: 27.5A

    With SF ≥ 1.15, maximum overload setting = 125% of nameplate FLA = 1.25 × 22A = 27.5A.

  4. Per NEC 430.32(C), if the standard overload setting is insufficient to start or carry the load for a motor with SF ≥ 1.15, the maximum allowable trip setting may be increased to:

    Answer: 140% of FLA

    NEC 430.32(C) permits the trip setting to be increased up to 140% of FLA for motors with SF ≥ 1.15 when the standard setting cannot carry the load.

  5. Per NEC 430.37, how many overload sensing elements are required for a 3-wire, 3-phase motor with no neutral conductor?

    Answer: 3 elements

    NEC 430.37 requires one overload sensing element in each of the three ungrounded phase conductors for a 3-wire, 3-phase motor.

  6. Per NEC 430.32(B), a motor with a nameplate marked 'thermally protected' may use the built-in thermal protector to serve as the overload protection, provided the protector is approved for use with the motor and will:

    Answer: Prevent dangerous overheating of the motor

    NEC 430.32(B) allows built-in thermal protectors as overload protection when approved for use with the specific motor and capable of preventing dangerous overheating.

  7. Per NEC 430.43, where the automatic restarting of a motor after an overload trip could be hazardous to personnel, which type of overload device is prohibited?

    Answer: Automatic reset overload relay

    Automatic reset overload relays are prohibited where automatic restarting after a trip would endanger personnel, as no human action is required to restart the motor.