In the previous lesson you learned how to start and configure the PLC simulator and
then download the software.
Now the simulator has my PLC program in it and I can start testing the logic
As the first step, to go to the online mode, I'll click on this "monitor on/off" icon in
the toolbar.
Ok the program is now in the online mode and connected to the simulator.
These green lines here show where I have the signal as true.
As I mentioned before, the stop switch that I'm using here is a normally closed switch.
That means since this switch is already closed, in the normal mode, it will let the signal
pass and because of that, the PLC input that this switch is connected to should already
be true.
Said differently, since this switch is already closed, the 24 volts signal can reach out
to the PLC input that this switch is connected to.
This switch is connected to the second input of the digital input card.
The address for this input is I0.1.
So I should see this input here on the simulator true.
But as you can see, here it shows me that this input is false.
Now why is that?
This is because I'm testing the program with the simulator.
If the software was connected to a PLC and I had an actual normally closed switch connected
to the PLC input, I would see this input as true in the online mode but since I'm currently
testing the PLC program with the simulator, the input is false here.
Now what I can do here?
Here I can simulate having a normally closed switch connected to the I 0.1.
How?
For that I can simply go ahead and make this input in the simulator true.
Now this works exactly as I've connected a normally closed switch to this input.
Ok.
Now everything is ready to test the PLC program.
As you already know the way that this logic should work is that when the start switch
is pressed, the main and star contactors should be energized at the same time and then after
an 8 second delay which is caused by this timer here, the star contactor should be de-energized
and the delta contactor should be energized all while the main contactor is still energized.
Now I'll go ahead and press the start switch.
As you can see by doing this, the main and star contactors are going to be energized
as expected and the timer starts timing as well.
After 8 seconds, when the timer is active, this open contact will be true and de-energize
the star contactor.
At the same time, since the timer is now active and the star contactor is de-energized, the
delta contactor is going to be energized in the last network.
Now in the first network, you see that the main contactor is still active.
So now I have both the main and the delta contactors active.
This is what you can see on the simulator as well.
The first output here is the main contactor which is true, the second one is the star
contactor which is false, and the third output is the delta contactor which is true.
Now if I press the stop switch once, the whole system stops and all of the outputs are going
to be false again.
So this shows that the PLC program works exactly as I expected to.
So to sum it all up, we like the Star-Delta concept of wiring and programming to alleviate
the inrush current that occurs when starting a motor.
We have written 14 lessons on this very important topic which demonstrates the complexity as
well as the usefulness of this approach.
Through this entire series we have walked you, step by step, through the theory, the
wiring, the programming, and the testing.
This is the last video presented for this useful concept and we have enjoyed producing
the series for you.
Not only did you gain some excellent knowledge about Star-Delta wiring of motors but you
also began dipping your toes into the PLC programming environment.
We hope you enjoyed this series and as always, greatly appreciate your “likes” below.
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