Question 61
A control circuit uses a normally closed stop pushbutton and a normally open start pushbutton for a motor starter. What happens if the stop button contacts fail open?
Question 62
A motor control circuit uses several limit switches in series to stop a conveyor if any guard is opened. What is the main safety advantage of wiring these devices in series?
Question 63
In a simple control circuit, a normally closed stop button is wired in series with the coil of a motor starter. What happens when the stop button is pressed?
Question 64
Which statement is true about a stop pushbutton in a typical motor control circuit?
Question 65
In a three-wire control circuit using a maintained 'Start' pushbutton and a 'Stop' pushbutton, what is the purpose of the auxiliary contact wired in parallel with the Start button?
Question 66
In a standard 3-wire control circuit for a motor starter with start and stop pushbuttons, what happens when the stop button is pressed?
Question 67
A motor starter coil is rated 120 V, but the motor will not start when the start button is pressed. Measurement shows only 80 V at the coil terminals when the button is pressed. Which is the most likely cause?
Question 68
In a standard three-wire motor control circuit with 'START' and 'STOP' pushbuttons, how are the contacts typically wired?
Question 69
In a control circuit, what is the normal contact type for a 'STOP' pushbutton in a 3-wire start/stop station?
Question 70
A 3-phase motor installation uses a magnetic contactor with auxiliary sealing contacts in the control circuit. What is the purpose of the sealing contact?
Question 71
A control ladder diagram shows a motor starter coil controlled by a start button, stop button, overload contact, and a seal-in contact. The motor will not stay on after releasing the start button. What is the most likely cause?
Question 72
An industrial control panel includes both power and control wiring. Which practice helps reduce electrical noise and interference in sensitive control circuits?
Question 73
A motor control circuit uses a maintained 'start' selector switch and a 'stop' pushbutton in series with a contactor coil. The motor occasionally fails to stop when the stop button is pressed. Which wiring issue could cause this?
Question 74
A control ladder diagram shows a normally closed stop pushbutton in series with a normally open start pushbutton and the coil. What happens when the stop button is pressed?
Question 75
A start/stop station controls a motor via a magnetic contactor. The motor will start when the start button is pressed but drops out as soon as the button is released. Which control circuit issue is most likely?
Question 76
A control drawing shows an emergency stop (E-stop) pushbutton wired normally closed and installed in the control circuit of several machines. Why is a normally closed contact used for this function?
Question 77
You are troubleshooting a control circuit where a motor starter coil does not energize. You measure correct control voltage at both sides of the coil when the start button is pressed, but the coil does not pull in. What is the most likely problem?
Question 78
In a control circuit using a maintained selector switch and a momentary start pushbutton, what is a common reason to include a seal-in contact on a motor starter?
Question 79
In a typical three-wire motor control circuit using start and stop pushbuttons and a contactor coil, how is the stop pushbutton wired so that pressing it will de-energize the motor?
Question 80
Which of the following is the best description of a 'line diagram' for motor control circuits?
Question 81
In an industrial control panel, a journeyperson sees that control wiring is separated from power wiring into different wireways. What is the MAIN reason for this practice?
Question 82
A control circuit uses a normally closed stop pushbutton and a normally open start pushbutton to control a motor starter. What happens when the stop pushbutton is pressed?
Question 83
A 480 V motor control center (MCC) bucket will not start the motor when the start button is pressed. The control circuit fuse is good, the overloads are reset, and there is line voltage present on all three phases. However, there is no voltage at the starter coil when the start button is pressed. Which component is MOST likely causing the issue?
Question 84
A control circuit uses a normally closed stop button and a normally open start button to energize a motor starter coil. What happens if the stop button contacts fail open?
Question 85
A motor control circuit uses an auxiliary contact for a seal-in (holding) circuit. After starting, the motor drops out as soon as the start button is released. Which fault best explains this symptom?
Question 86
When installing a motor control center (MCC), what is the function of the 'bucket'?
Question 87
What is the purpose of the 'holding contact' (seal-in contact) in a 3-wire motor control circuit?
Question 88
Which component is used to electrically isolate the control circuit from the power circuit in a motor starter?
Question 89
Which type of motor braking involves injecting DC current into the stator windings of an AC motor?
Question 90
In motor control, what is 'Jogging' or 'Inching'?