compact logix

Hi all,


Project philosophy is to switch between main power and stand by power .
So when the main power is cut I should signal the generator and vice versa .
What I am having is two air circuit breakers (ACB1 and ACB2 )in which one is connected to the main power and the other is connected to the generator .
When the main power fails I should stop ACB1 and give signal to the generator after few seconds I should start ACB 2 then when main power is obtained then I should stop ACB2 and generator ,then start ACB 1.
Like wise I have another same set with same function.
For which I have decided the inputs and output based on
v START/STOP
v TRIP ,ALARM
v DRAWOUT

This comes to around 19 inputs and 13 outputs.

So I am thinking of using the below configuration,
(ALLEN BRADLEY)
Ø 1769-L31 PLC

Ø 1769-PB2 POWER SUPPLY

Ø 1769-IQ32 Ex. Module (D.I)

Ø 1769-OW16 Ex. Module(D.O)

As always in need of your advice and suggestion .Any further information required do let me know.
Is the above configuration correct??? Or should I have to change.

Why are you doing this in a PLC and not an Auto Transfer Switch?

Also, if you do need custom functionality, I would probably use a micrologix for this. The only thing I see gained with a control logix is cost.

Hi brian ,

It is customer need thats why doing . And this PLC which I have mentioned in above post is just copy from previous project that is a differrent project which used same configuration . Now then you have mentioned micro logix I will browse for it mean while the philosophy seems to by modified which I will update shortly .

Thanks for your immediate response .

Yes, use ATS if at all possible.

Also, you definately need a UPS to allow the PLC to switch all the equipment. The UPS needs to be big enough to handle not only the PLC, but all the solenoids required for switching the ACBs. I would also size it big enough to perform a minimum of 4 switches of the system on a single battery charge.

You can also consider the AB Micro line of controllers if you want to save cost. I would consider that line along with the micrologix.

As long as you have the I/O covered, I would think that most any PLC would do the job you are asking it to do. You will also need an end cap (Terminating Resistor) for your configuration.

My main concern, would be that there is no possible way for ACB1 and ACB2 to be on at the same time. You will certainly need feedback, that these are open/closed, and I would prefer a mechanical interlock as well.

“Yes, use ATS if at all possible.

Also, you definately need a UPS to allow the PLC to switch all the equipment. The UPS needs to be big enough to handle not only the PLC, but all the solenoids required for switching the ACBs. I would also size it big enough to perform a minimum of 4 switches of the system on a single battery charge.

You can also consider the AB Micro line of controllers if you want to save cost. I would consider that line along with the micrologix. “
The customer wants these function to be automated that is the reason.
UPS yes we will use but about its rating and everything I have no idea now which I will update after receiving the details for sure
Micro line and micro I would look to it as I said the above PLC I just copied from the previous project .
Now then I have got some key word I would make a search on it .

As long as you have the I/O covered, I would think that most any PLC would do the job you are asking it to do. You will also need an end cap (Terminating Resistor) for your configuration.

My main concern would be that there is no possible way for ACB1 and ACB2 to be on at the same time. You will certainly need feedback that these are open/closed, and I would prefer a mechanical interlock as well.
1769-ECR RIGHT END CAP/TERMINATOR sorry I forgot to mention it any how I will look in to Micro logix and then again update my configuration . Also I will update accurate inputs and outputs with its philosophy shortly .

Thanks for your time and response . Will come with more information shortly .

The tricky part is going to be the UPS. If it is not up to the job then you are going to have some weird results.

Also as Brijim said you should have a linked set of contacts for the circuits. Something simliar to a reversing contact. This way only one can be on at a time feeding the system. Also on the generator side I would have a voltage meter that let me know when the generator was at speed befoe I brought my load online. Most generators can start up underload if the load is not to close to the generators max capicity.

So here comes the philosophy,

To make it clear understanding I have made a free hand sketch, please do correct me if there is any mistake.
View attachment Free hand sketch.pdf
Here we have two main power supplies (TF-1 & TF-2) and one generator.
We are using UV (Multifunctional relays) to sense for under voltage or over voltage or to sense the voltage.
When TF-1 is OFF UV-4 will give signal to the PLC and PLC will give signal to the generator.
There will few seconds gap for the generator to run after which UV-1 will give signal to PLC and ACB-1 will be started then again UV-5 will give signal to the PLC and ACB-5 will be started .
Same sequence will be followed by the other transformer (TF-2).
Here things which are considered for input and output are
· ACB ON/OFF - 1*7 - 7 I/p
· ACB TRIP – 1*7 - 7 I/p
· ACB DRAWOUT – 1*7 - 7 I/P
· UV – 1*7 -7 I/P
· AUTO/MANUAL -1 I/P
· POWER HEALTHY -1 I/P
TOTAL I/P -30 I/P
· ACB ON – 1*7 - 7 O/P
· ACB OFF – 1*7 -7 O/P
· ACB TRIP ALARM – 1*7 -7 O/P
· GENERATOR -1 O/P
· POWER HEALTHY - 1 O/P
TOTAL O/P -23 O/P
awaiting your suggestion , advice mean while I will post my configuration

Based upon inputs and outputs I have selected two configurations from Allen Bradley
FIRST CONFIGURATION: Compactlogix

1769-PB2 24 VDC INPUT POWER SUPPLY 2 AMPS @ 5 VDC OUTPUT

1769-L31 COMPACTLOGIX DUAL SERIAL PROCESSOR, 512K

1769-IQ32 24V DC, sinking or sourcing -------------------------------32i/p

1769-IQ6XOW4
24V DC, sinking or sourcing AC/DC n/o relay contact outputs 6i/p 4o/p

1769-OB16 24V DC, sourcing --------------------------------------------------- 16o/p

1769-OB8 24V DC, sourcing --------------------------------------------------------8o/p

1769-ECR RIGHT END CAP/TERMINATOR

TOTAL ----------------------------------------------------------------------38i/p 28o/p

SECOND CONFIGURATION:
MICROLOGIX 1200

1762-L40BXBR CPU -------------------------- 24i/p 16o/p

1762-IQ16 24V DC sink/source -----------16i/p

1762-OW16 AC/DC N.O. contact -----------------------16o/p

TOTAL---------------------------------------------- 40 i/p 32 o/p


I don’t know whether these configurations are correct if there is anything I have missed or if there is any mistake please correct me.

I don’t know which configuration is best suited for this application so I am waiting for your suggestions.

The PLC shouldn't be much of a concern. I didn't count your I/O, but both setups look ok. Either should handle the requirements of the application quite easily.

In this case, I don't think that the logic, or the PLC setup should be much of an issue. That part is fairly simple. It's the hard wiring and safety aspect of it, that should require the most attention. If an output goes bad, or a tech is trying to force an output, and turns on the wrong thing. You need to make sure TF1, TF2, and the Generator can never meet.

I wouldn't simply copy another system on this one (assuming it is OK). And if you are unsure at all, I would stay away from it. A system like this could be running for years, and never have a problem. But if there ever is a problem, it won't be a small matter with those 2500A breakers.

By your questions and work, I can tell that you are an intelligent person. Also by your questions, I would guess that you don't have much experience (which is fine, but most experienced designers aren't posting there I/O setup for confirmation) I've always maintained, that one of the most important qualities of a good Engineer/Tech (Maintenance) is being able to push themselves, when they are out of their comfort zone, but also knowing when to stop and say they need help or a task shouldn't be done.

Perhaps I'm wrong, you are a power engineer, and all this has been accounted for; we are just not seeing it. PLC's are a little new to you, so that is what you are questioning. I just want to make sure you are evaluating all the "what ifs" when dealing with multiple fairly large power supplies.

First of all I would like to thank you for your time and response.
Hope these covers most of the information.
Ø Using PLC for ATS function is just an additional Feature. Mechanical interlocks are also used.
Ø UV’s will sense the voltage in the line which in turn will give signal to the PLC and based upon which ACB’s will be controlled.
Ø After the generator is started, UV-1 will sense for the voltage and then after confirming the required voltage ACB-1 will be given signal, like wise each ACB has a UV, based upon which it will be started .
Ø All the ACB’s are MOTORISED
Ø All the outputs from the PLC will be connected to interface relay through which the motorized ACB’s will be connected
Ø Draw outs will be determined using a LIMIT SWITCH.
Ø Each ACB's have separate inputs for START and START (SHUNT TRIP AND SPRING RELEASE ) so two outputs are used .
Ø POWER HEALTHY is just used to indicate the status of power to the PLC .

And this is the sequence:

---------------generator--- acb-1-- acb-2-- acb-3-- acb-4--acb-5-- acb-6--acb-7

tf-1(on)
tf-2(on)---------- off --------off----- off -------off------ on----- off -----off ------on
-------------------------------------------------------------- -------------------------------------
tf-1(off)
tf-2(on) ----------on--------- on ----on-------off------ off-------on----- off- ----on
--------------------------------------------------------------------------------------------------
tf-1(on)
tf-2(off)----------- on------- on -----off--------on------on ------off ----on -----off
---------------------------------------------------------------------------------------------------
tf-1(off)
tf-2(off) -----------on-------- on-----on------ off------ off------- on-----off----off
-------------------------------------------------

Please correct me where ever I am wrong .Each of your post is valuable to me, so feel free to advice or correct me.

Hope the above sequence is correct if not, have look at the attached file . Sorry for the inconvenience .