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 Table 430.52, the maximum rating of an inverse time circuit breaker for a Design B, squirrel cage motor branch circuit is:

    Answer: 250% of FLA

    Table 430.52 allows a maximum inverse time circuit breaker rating of 250% of the motor's FLA for Design B squirrel cage motors.

  2. Per NEC Table 430.52, the maximum rating for a non-time-delay fuse used for branch-circuit short-circuit protection of a Design B squirrel cage motor is:

    Answer: 300% of FLA

    Table 430.52 permits non-time-delay fuses rated up to 300% of the motor's FLA for branch-circuit short-circuit and ground-fault protection.

  3. Per NEC Table 430.52, the maximum dual element (time-delay) fuse rating for a Design B squirrel cage motor is:

    Answer: 175% of FLA

    Dual element time-delay fuses are limited to 175% of the motor FLA for Design B motors under Table 430.52.

  4. Per NEC 430.52(C)(2), if the maximum standard inverse time breaker size cannot carry the motor's starting current, the breaker rating may be increased to a maximum of:

    Answer: 400% of FLA

    NEC 430.52(C)(2) allows the inverse time breaker to be increased to a maximum of 400% of FLA when the standard 250% cannot handle motor starting current.

  5. Per NEC 430.110(A), the ampere rating of the motor circuit disconnecting means must be at least what percentage of the motor's full-load current rating?

    Answer: 115%

    NEC 430.110(A) requires the motor disconnecting means to have an ampere rating of at least 115% of the motor's full-load current rating.

  6. Per NEC 430.52(C)(1), when the maximum calculated branch-circuit protective device rating does not correspond to a standard fuse or breaker size, the installer shall use:

    Answer: The next higher standard rating

    NEC 430.52(C)(1) permits rounding up to the next higher standard fuse or breaker size when the calculated maximum value is not a standard rating.

  7. Which of the following is listed in NEC 430.109(A) as an acceptable type of motor disconnecting means?

    Answer: Motor circuit switch rated in horsepower

    NEC 430.109(A) lists motor circuit switches rated in horsepower as an approved type of disconnecting means for motor circuits.