3 Motors to Run Using 'Start' and 'Stop' Pushbutton Switches but no Latch Coil

Just put a NC contact from each starter in the coil circuit of each other starter. First one On locks out the other two, you cannot start either (or any) unless all 3 are off.

So, each starter has 1NO and 2NC aux contact.

The NO of each one goes to the Start / Stop circuit as a Seal-In contact for the Start button.

NC #1 of Starter A goes in series with the Stop button of Starter B, NC #2 of A goes in series with the Stop button of Starter C.

Repeat.

Thanks Raef. But can you please represent this in Ladder Logic, I'm quite new to ladder logic and all it entails, I'm studying hard to know more. Thanks once again.

This is the best I can do with no-vertical-rail typography:

(1)---Start 1---(3)

(1)---1R,NO----(3)---2R,NC---3R,NC---Stop 1---(1R)---(2)

(1)---Start 2---(4)

(1)---2R,NO----(4)---1R,NC---3R,NC---Stop 2---(2R)---(2)

(1)---Start 3---(5)

(1)---3R,NO----(5)---1R,NC---2R,NC---Stop 3---(3R)---(2)

[All (n) of the same number hook up to each other; i.e., wire numbers.]

Thanks so much Tornado. But the challenge here is I dont want to make use of any Latched coil. Is that possible?

There may be a question of terminology about this. A "latched coil" relay could be a specific configuration such as in an "alternator."

If you are trying to avoid having an NO contact latch in a plain-Jane relay coil, I don't off hand know how (short of mechanical latching, which I guess we're avoiding).

What exactly needs to happen? For instance, if power is interrupted and then restored, should the pump come back on automatically, or only manually?

...What exactly needs to happen? For instance, if power is interrupted and then restored, should the pump come back on automatically, or only manually? ...No, the pump should only be started manually after a power interruption.

<...don't want to use a latching coil in the design...>

Why not?

To me, "latched" means a mechanical latching relay, one that has two coils, a Latch Coil and an Unlatch Coil. I did not mean that.

In my scheme, the concept is a "sealed-in" contactor. The coil is strictly one way, Energized or De-energized and you use a NO contact of the same contactor to seal the circuit around a momentary Start push button contact.

This is basic stuff. I suspect you are either a student or you are not an Engineer. Please go through the following basic courses from the beginning to learn how motor controls work, then post your questions on anything that you did not understand.

Basics of Control Components

Thanks so much everyone. During my undergraduate days we never went into motor control this deeply. I am doing a personal development in understanding all of these. In doing that, someone confronted me with this question and says it is a possibility. I came up with a latch and unlatch Motor solution but he insisted there is a way around it. Thanks once again. I find your responses really enlightening.

You need 3 circuits, with NC contacts from the other two motor starters in series with the one being controlled. This way, once one circuit is running the other two are inhibited from running. The NC Stop is a normally closed, push to open, pushbutton and the NO Start is a normally open, push to close, pushbutton. The NO MS? contact is called a holding contact and will normally hold the energized motor starter in as long as the NC stop button isn't pushed. Note: This is not a latch motor starter coil since removing power from the circuit will cause any energized motor starter coil to return to the "off" state.

.NC MS2 ..NC MS3 .. NC Stop 1 ......NO Start 1

---]/[------]\[--------o o-------------o o-------------(MS1)-------

............................................|....... MS1......|

............................................|-----] [-------|

NC MS1 NC MS3 NC Stop 2 NO Start 2

---]/[------]\[--------o o-------------o o-------------(MS2)-------

............................................|....... MS2......|

............................................|-----] [-------|

.NC MS1 ..NC MS2 ..NC Stop 3 .......NO Start 3

---]/[------]\[--------o o-------------o o-------------(MS3)-------

............................................|....... MS1.......|

............................................|-----] [-------|

Note: I had to space the components with dots since the editor removed all extra spaces I'd put in to align the diagram.

I hope this helps.

Greg

Good one. i assume you intend to wire one NO contact of the contactor across the Start NO pb for the 'hold' action?

Toba says "Starting one motor stops any running motor". This is not achieved here i think ?

A follow up:

I just reread the original question. He wanted pressing any start button to drop out the other two starters and pick up the selected starter.

This can be accomplished by adding a second NO contact on each start pushbutton and wiring it in parallel with the two MS NC contacts at the start, left end, of each of the individual motor starter's rungs of logic.

Presing a start button will energize the selected MS contactor. The NC contacts on that MS contactor will drop out any other MS contactor that is energized, stopping any motor except the selected one.

Thanks,
Greg

Thanks so much Greg and Kvsridhar. Everyone in fact.

I finally thought of the solution and it someway aligns with your contributions.

I will post that up soon.

Regards all.

Try this

Struggling with image upload.

Please help, I need a way to upload images directly from my pc, so I can show y'all the solution I came up with. Similar concepts but different design. I saw part of a discussion in the forum on image upload, but it doesn't correlate at all with the edit page i see here. ...So now you have the file in your system, Left Click in the Text Editor in the Forum, (where you want that graphic), go to the small button which looks like a camera... Regards.

This is a slight variation from before. This one uses Start pushbuttons having one NO contact for starting the desired pump, and two NC contacts to stop the other pump(s). I think you have to have the NO holding contact for each pump, or else what keeps it going once you release the Start button?

(1)---Start 1---(3)

(1)---1R,NO----(3)---Start 2,NC---Start 3,NC---Stop 1---(1R)---(2)

(1)---Start 2---(4)

(1)---2R,NO----(4)---Start 1,NC---Start 3,NC---Stop 2---(2R)---(2)

(1)---Start 3---(5)

(1)---3R,NO----(5)---Start 1,NC---Start 2,NC---Stop 3---(3R)---(2)

Yes! that's exactly the concept I came up with. . I think you have to have the NO holding contact for each pump, or else what keeps it going once you release the Start button? And yes at that...In my design I simply connected the motor NO contact in parallel to the start of each Motor and then connected the stop NO contact for each motor to a memory output.