Practice Test Geeks(CEP) Certified Electrical Professional Practice Test
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Motor Control & Drive Systems Flashcards

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

Read the first 7 Motor Control & Drive Systems flashcards as text

  1. What is the primary energy-saving advantage of using a VFD for centrifugal pump and fan applications?

    Answer: Significant energy savings by reducing speed to match actual load demand, since power varies as the cube of speed

    The affinity law states that power varies as the cube of speed for centrifugal loads, so even a 20% speed reduction yields approximately 49% power savings.

  2. In motor control terminology, 'jogging' (or 'inching') refers to:

    Answer: Momentarily energizing the motor to move a load by small increments without engaging the run circuit

    Jogging momentarily energizes the motor contactor to move a load incrementally, bypassing the motor's normal holding circuit so the motor stops when the jog button is released.

  3. According to NEC Article 430.22, motor branch circuit conductors must be rated at not less than what percentage of the motor's full-load current (FLC)?

    Answer: 125% of FLC

    NEC 430.22 requires motor branch circuit conductors to be sized at no less than 125% of the motor's full-load current to account for continuous operation.

  4. A motor nameplate shows a service factor (SF) of 1.15. This means the motor can:

    Answer: Handle 115% of its rated horsepower load on a continuous basis without damaging overheating

    A service factor of 1.15 means the motor can operate continuously at 115% of its rated horsepower under normal voltage and frequency conditions.

  5. A 9-lead dual-voltage motor can be reconnected for high-voltage operation by wiring the windings in:

    Answer: Series, increasing the voltage across each winding group

    For high-voltage operation, the two winding groups are connected in series so each group sees half the total line voltage, matching the winding insulation rating.

  6. According to NEC Article 430, motors rated over 1 horsepower that are not continuously attended must be provided with:

    Answer: Running overload protection that automatically disconnects the motor if it overheats

    NEC 430.31 and 430.32 require running overload protection that automatically disconnects motors from the supply when an overload condition causes dangerous overheating.

  7. The locked rotor current (LRC) of a typical NEMA Design B AC induction motor is approximately how many times the motor's full-load current (FLC)?

    Answer: 6 to 8 times FLC

    NEMA Design B motors typically draw 6 to 8 times their full-load current at locked rotor (stall) conditions, which is why branch circuit overcurrent protection is sized generously.