Electrical Systems and Controls Flashcards
7 cards from real Millwright Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems and Controls flashcards as text
What is the purpose of a control transformer in an industrial motor control panel?
Answer: To step down line voltage to a safe level for control circuit devices
A control transformer steps down the 480V line voltage to 120V (or similar), providing a safe, lower voltage for operating relays, pilot lights, pushbuttons, and PLCs.
Which device uses a small coil current to electromagnetically operate contacts that switch a larger load circuit?
Answer: Control relay (pilot relay)
A control relay uses a low-power coil signal to operate contacts rated to switch higher currents, allowing a small control signal to energize or de-energize a heavier load.
What does PLC stand for in industrial automation and control systems?
Answer: Programmable Logic Controller
PLC stands for Programmable Logic Controller, a ruggedized industrial computer that executes ladder logic or other programs to automate machinery and processes.
When performing lockout/tagout (LOTO) on electrical equipment, what is the FIRST step a millwright must complete?
Answer: Identify all energy sources associated with the equipment
OSHA LOTO procedures require identifying all hazardous energy sources first so that none are overlooked during isolation, preventing unexpected energization.
What is the key difference between a normally open (NO) and a normally closed (NC) contact in a relay?
Answer: NC contacts pass current at rest; NO contacts pass current only when energized
A normally closed (NC) contact conducts in the de-energized (rest) state, while a normally open (NO) contact only conducts when the relay coil is energized.
What is the function of a limit switch in an automated industrial system?
Answer: To detect the physical position of a machine component and signal the control system
A limit switch uses physical contact with a moving machine part to signal the control system when a specific position has been reached, triggering the next step in a sequence.
Which type of single-phase motor uses a capacitor in series with the auxiliary winding to develop adequate starting torque?
Answer: Capacitor-start induction-run motor
A capacitor-start motor places a capacitor in series with the start winding, creating the phase displacement between run and start winding currents needed to produce a rotating magnetic field for starting.