Consider the problem ATS $($Automatic transfer switch$).$ Draw the ladder diagram of the system and write the instruction list.

The ATS is working according to the following sequence

Fault condition

If any phase of the main source is out:$-$

instantaneously $,$ disconnect the main source through it's contactor

after time delay T$1$ start the generator field

after time delay T$2$ guild up generator voltage

check the generator o$/$p voltage through the relay

if yes stable for a time period T$3$ connect the generator through It's contactor

Normal condition

If non of the main phases is out

if yes& stable for time period T$4$ disconnect the generator through it's contactor

after a time delay T$5$ connect the main through it's contactor

after time delay shut down the generator unit $[$disconnect the field$]$