Practice Test GeeksIEC - Independent Electrical Contractors Practice Test
← All IEC Flashcard Decks

Motors and Motor Controls Flashcards

7 cards from real IEC 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 Motor Controls flashcards as text

  1. A motor disconnecting means must be within sight of the motor and its driven machinery. 'Within sight' is defined by the NEC as visible and not more than:

    Answer: 50 feet

    Per NEC 430.102, 'within sight' means visible and not more than 50 feet distant from the motor and driven machinery.

  2. What is plugging as a method of motor braking?

    Answer: Reversing the phase sequence of the motor while it is running to create braking torque

    Plugging reverses the phase sequence applied to the motor while it is still rotating, creating a reverse rotating field that produces braking torque.

  3. Which of the following best describes a split-phase motor?

    Answer: A single-phase motor with two windings (main and auxiliary) displaced in time and space to create a rotating field

    Split-phase motors use a main running winding and an auxiliary starting winding with different impedances to create phase displacement and a rotating magnetic field.

  4. What is the primary advantage of a capacitor-start motor over a standard split-phase motor?

    Answer: Higher starting torque due to greater phase displacement between windings

    The capacitor in the starting circuit creates nearly 90° phase displacement between the main and auxiliary winding currents, producing significantly higher starting torque.

  5. In a motor control ladder diagram, the symbol for a normally open (NO) contact that is controlled by a pushbutton is:

    Answer: Two vertical lines with a diagonal line between them representing the actuator

    In ladder diagrams, a normally open pushbutton contact is represented by two vertical lines (the contact symbol) with a slanted line representing the actuator arm.

  6. The maximum rating of a dual-element (time-delay) fuse used for motor branch circuit short-circuit protection per NEC 430.52 for a Design B motor is:

    Answer: 175% of motor FLC

    Per NEC Table 430.52, the maximum rating for dual-element time-delay fuses protecting NEMA Design B motors is 175% of the motor's full-load current.

  7. A motor controller's SCCR (Short Circuit Current Rating) must be equal to or greater than:

    Answer: The available fault current at the point of installation

    The SCCR of a motor controller must be equal to or greater than the maximum available fault current at the terminals of the controller.