Journeyman Electrician's Motors and Motor Controls Flashcards
7 cards from real Journeyman Electrician’s Exam practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Journeyman Electrician's Motors and Motor Controls flashcards as text
In a two-speed motor (consequent pole), changing from low speed to high speed requires:
Answer: Reconnecting the stator windings to change the number of effective poles
Consequent pole motors change speed by reconnecting stator windings to alter the effective number of magnetic poles, which changes synchronous speed.
What is the primary function of the overload relay in a magnetic motor starter?
Answer: To protect the motor against sustained overcurrent that causes overheating
Overload relays protect the motor from sustained overcurrent (overloads) that would cause excessive heat buildup and winding damage over time.
According to NEC 430.32(A), a continuous-duty motor with a service factor of 1.15 must have overload protection set to trip at no more than what percentage of nameplate FLA?
Answer: 125%
NEC 430.32(A)(1) requires overload protection to trip at not more than 125% of FLA for motors with a service factor of 1.15 or higher.
A 'wye-delta' reduced-voltage starter transitions the motor from wye to delta configuration. What is the purpose of this transition?
Answer: To reduce starting current to approximately 1/3 of across-the-line current during start
During wye starting, each winding receives line voltage ÷ √3, reducing starting current to about 1/3 of across-the-line (delta) starting current.
Under NEC Article 430, the term 'controller' refers to:
Answer: Any switch or device used to start and stop a motor
NEC 430.81 defines a controller as any switch or device that is normally used to start and stop a motor by making and breaking the motor circuit current.
A motor's NEMA enclosure type '4X' indicates the enclosure is:
Answer: Watertight, dust-tight, and corrosion-resistant
NEMA Type 4X enclosures are watertight, dust-tight, and constructed of corrosion-resistant material for demanding indoor or outdoor applications.
A jogging (inching) circuit differs from a standard start/stop circuit because:
Answer: The holding contact (seal-in) is bypassed so the motor runs only while the jog button is held
In a jog circuit, the memory (seal-in) contact is not energized, so releasing the jog button immediately de-energizes the contactor and stops the motor.