The physically executed power demand indicator is programmed with microprocessors in medium and large scale industries. The main setback in the demand indicator functioning using microprocessor circuitry is that it works on an unchanged program, thus, the once set command level can not be changed suiting the fluctuations requirements in loads. To address above problems, a program PLC is suggested in the microprocessor circuitry place. This has offered for elasticity in changing the maximum order level costuming to the fluctuations in the load. PLC is a controlling appliance comprising of a programmable processing unit with specialized computer languages. Characteristically the program is written in an environment development on a PC and is downloaded on to a PLC directly via a cable. The program is saved in a non-volatile PLC memory. The circuitry of PLC monitors the multiple sensor inputs status, which control the actuators output like the solenoids of motor starters. A single circuitry of PLC controls all the above each output actuators. The circuitry of PLC provides a wide range of functions with controls of relay, controls of motor, controls of process, complex networks as well as dispersed control systems. In the current work a circuitry of PLC is built relating to power distribution.
The industrial PLC specifies total power from the unit of supply and controls the distribution to the non-manufacturing and manufacturing fields of the industry through the periods of demand beyond a certain level.
In early 20th century, microprocessors are applied for controlling distribution of power among a variety of units of an industry. The microprocessor applications experience from a basic limitation that it fails to modify the maximum order level during load fluctuations. This has effected in PLC circuitry development to be integrated in the microprocessor place, in order that the order level can be changed to suit the load variations resulting in a continuous power distribution and smooth uninterrupted. PLCS are miniature individual computers using software and hardware to carry out the functions of control.