Practice Test Geeks(E2) E2 Commercial Electrical Inspector Practice Test
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Motors and Transformers Flashcards

7 cards from real E2 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Motors and Transformers flashcards as text

  1. A 3-phase synchronous motor operating at unity power factor is often used in commercial facilities primarily to:

    Answer: Correct lagging power factor on the electrical system

    Synchronous motors operating at leading power factor act as capacitors, supplying reactive power and correcting lagging system power factor.

  2. Per NEC 450.14, transformers must be provided with a means to disconnect all ungrounded conductors. For a transformer rated over 600V, this disconnect must be:

    Answer: Lockable in the open position if not within sight

    NEC 450.14 requires a transformer disconnecting means that is either within sight or capable of being locked in the open position.

  3. Which motor starting method produces the lowest inrush current to the power system?

    Answer: Solid-state soft starter

    Solid-state soft starters using SCRs to ramp voltage minimizes inrush current more precisely than mechanical reduced-voltage methods.

  4. When a motor control circuit is derived from a control transformer, NEC 430.72(B) requires the control circuit conductor to be protected at no more than:

    Answer: The ampacity of the smallest conductor in the circuit

    NEC 430.72(B) requires control circuit conductors to be protected by an OCPD rated no more than the ampacity of the smallest conductor.

  5. The 'kVA' rating on a transformer nameplate represents:

    Answer: The apparent power capacity under rated conditions

    kVA is the product of rated voltage and rated current (apparent power), not accounting for load power factor.

  6. Per NEC 430.102(A), the motor controller disconnecting means must be located within sight of the controller. 'Within sight' is defined as:

    Answer: Visible and not more than 50 feet away

    NEC Article 100 defines 'within sight' as visible and not more than 50 feet from one another.

  7. A motor nameplate shows 'SF 1.15'. This means the motor can safely operate continuously at:

    Answer: 115% of its rated horsepower with acceptable temperature rise

    A service factor of 1.15 means the motor can operate at 115% of its nameplate HP with acceptable temperature rise under rated voltage and frequency.