CPM - Certified Plant Mechanic Electrical Systems and Controls Flashcards
6 cards from real CPM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CPM - Certified Plant Mechanic Electrical Systems and Controls flashcards as text
What is the primary function of a contactor in a motor control starter circuit?
Answer: Switch high-voltage power to the motor coil
A contactor is an electromechanically operated switch that connects and disconnects the main power supply to the motor based on control circuit signals.
What does the abbreviation DOL stand for in motor starting methods?
Answer: Direct On Line
DOL (Direct On Line) starting connects the motor directly to full supply voltage, resulting in high inrush current at startup.
A star-delta (Y-Δ) starter reduces motor starting current to approximately what fraction of the DOL value?
Answer: 1/3
Star-delta starting reduces inrush current to approximately 1/3 of the DOL starting current by initially connecting windings in star configuration.
What is the purpose of a control transformer in a motor starter panel?
Answer: Step down voltage to a safe level for the control circuit
A control transformer steps line voltage down (typically to 120 V or 24 V) to power the control components such as relay coils and pilot devices.
Which type of motor control device allows a motor to run in both forward and reverse directions?
Answer: Reversing starter
A reversing starter uses two contactors wired so that energizing the second contactor swaps two of the three phase leads, reversing motor rotation.
What is the main purpose of a motor circuit disconnect switch?
Answer: Isolate the motor from power for safe maintenance
A disconnect switch provides a visible means to de-energize and lock out the motor circuit before performing maintenance, per OSHA LOTO requirements.