Somebody can help???

[Lan]

Hello:

I'm very curious about PLC but I don't know much about that. I have a question to solve:
For changing the set-point of an automatic votage regulator(AVR)I need to have an up/down ramp with values between the limit 0 to + 10V dc.
How can I use a PLC to do this?

Thank you

 

[DesertDog]

In terms as general as the specifications given... Connect an analog output card to the PLC capable of a -/= 10V or 0-10V output. Write a program to ramp from 0 to the max output value (Depends on PLC used) at the rate needed, where 0 = 0 volts and max output value = 10 V.

 

[The Hien]

Hi LAN,
Desert Dog's idea is right. please tell me what type of PLC you
are using, i can help you more.
................
Tran The Hien banghead

 

[Lan]

Hello The Hien


Thank you very muuch for your kind help. I can use a Siemens or OMRON PLC. It will be a dedicated PLC for this function.

My problem is how todo that.

I wait for your sugestion.

Thanks

Lan

 

[The Hien]

Hi LAN,
About your application, tell more details about it. For example :
- you need a 0-10V signal to control AVR.
But you want to set the desired value by hand or automatically by a program
- How many AVR you have
....All things about your application
According to it, i can help you a good solution!

Do you think you really need PLC to do that ?

Using PLC, you need: PLC CPU (Siemens or Omron as you said), power supply unit (24 VDC), analog output module (0-10V output signal) and a user - machine interface (it is a place where you can set desired value for AVR, it can be a computer with SCADA software,...)
But if you want to control your AVR automatically by a program, you don't need a user-machine interface.

About Siemens and Omron PLC, are you familiar with them ?
Do you have manuals ?
i am ready to help you !
Forgive me, i ask you a private question: is LAN a Vietnamese name ?
Bye
.........
Tran The Hien

 

[zezito]

Hi Lan
i have some experience on siemens plc's, and i think you should first to look if you have the right instructions on your plc
i.e. siemens 2xx has diferent functions compare to S7 3xx and S7 4xx.
what is the aplication for that program?

i am ready to give some help

 

[Lan]

Hello:

First of all I wish to thank to "The Hien" and 2zezito" for beeing so kind and so interested on helping me.
I'm going to try to decribe in more detail the aplication and what I need:
An AVR is an automatic voltage regulator, ie, an equipment that is used to regulate or control the excitation of a generator (alternator) in order to controll the reactive load. Normaly, it can work on two different ways: Constant power factor or constant reactive power.
Supose that we want to work on constant power factor but with diferent set-points during the thay, ie, PF=0.8 between 8AM to 8PM (during the day)and PF=1 between 8PM to 8AM ( during the night).
To work with PF=0.8 I need to aplly a voltage of 9V dc, for example, and to change to PF=1 I need to change the input voltage to 0V or 0.5V dc.This values will change every day according to the clock.
The order to change the PF from one value to other is given by a potential free contact that exists on the energy counter and that changes from close to open or viceversa depending from a signal sent throw the grid by the energy distributing company ( Like EDF infrance). Intead of a 0 to 10V signal, a 4 to 20 mA signal can also be used. This is the real aplication I need.I hope I have been clear.

I'll be very pleased if you can help.

P.S. I'm not from Vietnam, but from Portugal beerchug


Good by and thank you


Lan

 

[khalil]

its easy...

hi Lan ,

you can use S7 200 siemens(optional), you need a RTC (real time clock) to control the avr during day time according to your requirements.
and you need an analog output module to 0-10v to be connected from your plc to the avr.

are you familiar with s7 200(microwin)??

 

[zezito]

hi
khalil is right all you need is an anallogue output that you'll connect to the avr and something that can count the hours or minuts that your mode it's ON/OFF, and yes, a s7 2xx it's enough!
all the rest is programing, know how to program a S7? if you need i can give more information

by the way i'm also portugues!

 

[Lan]

Thak you khalil, Obrigado Zezito.

I think I was not clear enough: I don't need a clock becaus the order to change from one set-point to the other is given by the contatc existing in the energy counter: on it opens I must get a certain voltage and when it closes I must have another one: any of them between 0 to 10 V but diferent.

I underestand that an S200 + an amallogue card output must be used, but I'm not familiared wthi S7 and so, any help is welcome.


Thank you both once again

Regards

LAN

 

[khalil]

IT is NOt a "must"

hi LAN,

its not a Must its an option cause you said :

I can use a Siemens or OMRON PLC

you can use any plc with an analog output card...its simple ..



good luck with your efforts


regards.khalil

 

[DesertDog]

Figure the Voltage you want and move the required values into the output word according to the porportion relationship of 0=0 and 10=27648. Move one value into the output when the contact is closed and move the other value in when the contact is open.

Contact     |------|

--| |-------| MOVE |

            |      |

     10000  |      | Output

            |      |

            |------|



Contact     |------|

--|/|-------| MOVE |

            |      |

     20000  |      | Output

            |      |

            |------|

 

[Lan]

Dear DesertDog

I have 2 questions:

How did you get the value 10=27648 ?

In my case I must have an up and down ramp between the programed values. How can I doo that?

Thank you

 

[DesertDog]

Dear DesertDog

I have 2 questions:

How did you get the value 10=27648 ?

In my case I must have an up and down ramp between the programed values. How can I doo that?

Thank you

1. RTFM found here. Page 219 (4-13) covers value representation.

2. The voltage will follow the numerical value. Ramp this value using a timer, ramp function, or simply add/subtract a value to/from it each scan until the upper/lower limit is reached.

 

[Lan]

Tank you very much, Desert Dog

Regards