How can design ladder diagram

Jayaprakash,

Your posts today puzzle me. The other one about sizing an induction motor's OLR presumes it is "across the line" or DOL type starting in which the motor leads see the full load current of the motor's nameplate. This post, if it is referring to the same motor suggests you are considering a type of reduced voltage starter known as a wye-delta or star-delta starter. For it, there are two sets of motor leads with OLR's for each set. They are set at 57% of the motor's nameplate current, if I remember correctly.

Look at the manufacturer's literature for a star-delta starter. You should see a diagram of its three contactors, in which two are mechanically and electrically interlocked as well as a timing relay to control the transition. An important question is whether the starter is "open transition" or "closed transition". For a closed transition star-delta starter, the wiring gets more complicated with a few more components.

I will not tell you more than this on how to design the ladder diagram for such a starter. If you know enough to be safe, you can take the manufacturer's wiring diagram and translate it into a PLC's ladder format. If this is homework, people on this site don't take kindly to doing it for you.

--John M.

Thank you Mr.john.I need time to understand your's coments.

THANK YOU.

The starter equipment should be self-sufficient in controls to carry out its own star-delta transformation. The PLC should be sending a simple "run" output, and the drive should be doing all the rest. For one thing, the PLC cannot carry out the required mechanical interlocking between the various contactors on the drive; otherwise a forced output from the PLC at the wrong time could prove disastrous....

Thank you to all for very valuable coments

In the starting position stator wdg is Star connected and runing will be in delta.

Connect the coil contact in star as well as delta during the starting energize the coil, which is corresponding to star connection. After that turn off & on Delta coil..

Good day jayaprakash, Take the good advice from jmueller & PWslack. enough said. regards, leon

If you request, from GE Fanuc, MCC division, they can give you the ladder logic diagram for the PLC.