Practice Test Geeks(CEP) Certified Electrical Professional Practice Test
← All CEP Flashcard Decks

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. In a star-delta (wye-delta) motor starting method, the motor windings are initially connected in:

    Answer: Star (wye) configuration, reducing voltage across each winding to approximately 58% of line voltage

    During starting, windings are connected in wye (star), reducing the voltage across each winding to approximately 1/√3 (58%) of line voltage and reducing inrush current.

  2. The synchronous speed of a 4-pole AC induction motor operating on a 60 Hz supply is:

    Answer: 1800 RPM

    Synchronous speed = (120 × frequency) / number of poles = (120 × 60) / 4 = 1800 RPM.

  3. What is the primary role of a programmable logic controller (PLC) in a motor control system?

    Answer: To automate and sequence motor control operations based on programmed logic and input signals

    PLCs execute ladder logic or other programs to automate starting sequences, interlocks, and process control functions for motor systems.

  4. A motor has a synchronous speed of 1800 RPM and runs at an actual speed of 1750 RPM. What is the motor's slip?

    Answer: 2.78%

    Slip = (synchronous speed − actual speed) / synchronous speed × 100 = (1800 − 1750) / 1800 × 100 = 2.78%.

  5. Which NEMA enclosure type is rated 'watertight' and protects motor control equipment against hose-directed water?

    Answer: NEMA 4

    NEMA 4 enclosures are watertight and protect against hose-directed water from any direction, suitable for wash-down industrial environments.

  6. Regenerative braking in a VFD system works by:

    Answer: Converting the motor's kinetic energy back into electrical energy returned to the power supply

    Regenerative braking converts deceleration energy back into electrical energy fed to the supply grid, recovering energy rather than dissipating it as heat.

  7. What is the primary purpose of a dynamic braking resistor (DBR) connected to a VFD?

    Answer: To absorb and dissipate as heat the energy generated when the motor decelerates

    Dynamic braking resistors dissipate as heat the back-EMF energy generated by the motor during deceleration, providing controlled braking torque.