Electrical question -Motor Control

Thread Starter

Kley

Joined Feb 4, 2021
6
20190B58-BE11-4DA1-99AE-FC3FEB63BC0B.jpeg

Had this exam question that I got wrong and was wondering if someone could help me out with the answer
 

jpanhalt

Joined Jan 18, 2008
11,088
Here's a typical run-stop relay circuit (source:Google):

1612537117935.png

Is that what you were required to show?

1) Note how once started, the start relay stays closed until the current to its coil is stopped by opening the stop switch. The start switch opens as soon as it is released. Of course there are variations on that. In your circuit, I don't see how the stop switch interrupts current to the start relay.

2) If that was a timed test, there is probably an excuse for a less than perfect schematic. If it was not a timed test, I would recommend cleaning up the schematic before submitting.
 

Thread Starter

Kley

Joined Feb 4, 2021
6
Here's a typical run-stop relay circuit (source:Google):

View attachment 229593

Is that what you were required to show?

1) Note how once started, the start relay stays closed until the current to its coil is stopped by opening the stop switch. The start switch opens as soon as it is released. Of course there are variations on that. In your circuit, I don't see how the stop switch interrupts current to the start relay.

2) If that was a timed test, there is probably an excuse for a less than perfect schematic. If it was not a timed test, I would recommend cleaning up the schematic before submitting.
Yes it was timed and I was rushed but I drew it like that.... because you just had to change the Schematic that was given
Here's a typical run-stop relay circuit (source:Google):

View attachment 229593

Is that what you were required to show?

1) Note how once started, the start relay stays closed until the current to its coil is stopped by opening the stop switch. The start switch opens as soon as it is released. Of course there are variations on that. In your circuit, I don't see how the stop switch interrupts current to the start relay.

2) If that was a timed test, there is probably an excuse for a less than perfect schematic. If it was not a timed test, I would recommend cleaning up the schematic before submitting.
So it was timed and I have to just get it done... also from the info that you gave me I’m thinking of something like this... I did this on my phone so I apologize for how crappy it looks5564BEBC-3749-4367-BF3B-F6A5BD3A8B0D.jpeg
 

MaxHeadRoom

Joined Jul 18, 2013
23,104
BTW, I forgot to mention that the old way of connecting the overloads on the R.H. side of the coil is considered a NO-NO now.
They should be on the L.H. side.
The Schneider diagrams show the old way.
It was customary to do this on early Stop/Start stations as it reduced the wiring slightly.
Max.
 

jpanhalt

Joined Jan 18, 2008
11,088
Yes it was timed and I was rushed but I drew it like that.... because you just had to change the Schematic that was given

So it was timed and I have to just get it done... also from the info that you gave me I’m thinking of something like this... I did this on my phone so I apologize for how crappy it looks
Your post is a essentially a duplicate of what I posted. Don't you see how that would apply to a 3-phase motor/load? This is homework. Let's see your best answer (time is not an issue) and work on that. Hint: You cannot just disconnect one phase.
 

Thread Starter

Kley

Joined Feb 4, 2021
6
image.jpg
So I asked around and they said that there looking for us to look at the given wiring diagram. They want us to look at the start/stop motor circuit part of the diagram and draw it out in Ladder form. But yes you are correct in what you said, basic start/stop motor Diagram.
 

MaxHeadRoom

Joined Jul 18, 2013
23,104
In the 'Wiring Book' I posted, the ladder formats start on page 16.
As I mentioned, they are using the older non-approved method of O/L position in the ladder.
You should also reference the AUX contact as being part of the M contactor. e.g. M or M aux.
M cannot be the motor itself as the AUX has to be part of a control relay or contactor.
IOW you need to include the 3ph motor circuit also.
Max.
 
Top