Practice Test Geeks(EETC) Electrical Technician Certification Practice Test
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Motor Controls Flashcards

7 cards from real EETC 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 Controls flashcards as text

  1. What is the purpose of a Variable Frequency Drive (VFD) in motor control?

    Answer: To control motor speed by varying output frequency and voltage

    A VFD controls AC motor speed and torque by varying the frequency and voltage of the power supplied to the motor.

  2. Which NEMA enclosure type is required in locations where ignitable concentrations of flammable gases or vapors may exist?

    Answer: NEMA 7

    NEMA 7 enclosures are rated for Class I, Division 1 hazardous locations where flammable gases or vapors may be present.

  3. In a jogging (inching) circuit, what prevents the seal-in contact from latching the contactor ON?

    Answer: A jog/run selector switch that breaks the holding circuit path during jogging

    The jog selector or jog button arrangement breaks the path to the seal-in contact, so the contactor energizes only while the jog button is held.

  4. What is the effect on motor starting torque when using an autotransformer starter set to the 65% voltage tap?

    Answer: Torque is reduced to approximately 42% of full-voltage starting torque

    Starting torque varies as the square of the voltage, so at 65% voltage, torque is 0.65² ≈ 42% of full-voltage starting torque.

  5. A motor control center (MCC) bucket typically contains which combination of components?

    Answer: A circuit breaker or fuses, contactor, overload relay, and control wiring

    An MCC bucket is a self-contained unit housing the disconnect, protection (fuses/breaker), contactor, overload relay, and associated control wiring.

  6. What causes 'single phasing' in a three-phase motor, and what is the typical result?

    Answer: One phase conductor opens; motor continues to run but overheats and eventually fails

    Single phasing occurs when one supply phase is lost; the motor may continue running on two phases but draws excessive current and overheats.

  7. In PLC-based motor control, what is a 'rung' in ladder logic?

    Answer: A horizontal line in a ladder diagram representing one control logic statement

    A rung is one horizontal row in a PLC ladder diagram, containing input conditions (contacts) and one or more output coils or instructions.