Machines; Motor Control Labs Flashcards
To which terminals on a nema magnetic motor starter are the control wires connected?
2, 3
What terminals on a nema magnetic motor starter are used for motor connections?
T1, T2, T3
Nema holding contact numbers?
2,3 and 4,5
What is an issue with having the N/O start button in parallel with the N/C stop button? As opposed to in series.
Motor can run even if stop button is depressed
When wiring 2 start/stop stations to a motor starter, how many wires should we have in each of the following cases:
1) furthest start/stop to junction box
2) closest start/stop to junction box
3) from controller to junction box
3
4
3
What does an ohmmeter measure when connected across L2 and 3 on a reversing magnetic motor starter?
1) in a normal condition?
2) when reverse contactor is pushed in?
1) resistance of the forward coil
2) Open line; NC contact operated by reverse contactor has been opened.
Can the reverse contactor of a reversing magnetic motor starter be pushed in while the forward contactor is being pushed?
No: mechanically interlocked
How many overload contacts required for a reversing magnetic motor starter?
1
What type of contacts are required on a pushbutton to allow changing from one direction to the other without pressing the STOP button?
Mechanically interlocked
In a reversing magnetic motor starter with 2 start/stop stations, how are each of the following wired:
1) stop buttons with respect to eachother
2) fwd-start with respect to eachother
3) rev-start with respect to eachother
Series
Parallel
Parallel
How are the N/C contacts of a reverse-start button wired with respect to the forward holding circuit (for a reverse magnetic motor starter)
In series with the forward holding circuit
How can you tell if a motor control circuit will have positive jogging, just by looking at the schematic?
Positive jogging circuits will utilize either:
- selector switch
- additional relay w/ 2 N/O contacts
Will a regular NO/NC switch provide positive jogging?
No. Quick release of button may not give holding contacts time to open.
If a selector switch is used to provide jogging on a motor, it is connected in (series/parallel) with the holding contacts
Series
What is a disadvantage of using a selector switch to jog a motor?
Switch must be turned to jog, then start button pressed to jog.
