what is SCADA?
Supervisory control and data acquisition is a computer system for gathering and analyzing real time data. SCADA systems are used to monitor and control a plant or equipment in industries such as telecommunications, water and waste control, energy, oil an d gas refining and transportation. SCADA systems were first used in the 1960s and are now an integral component in virtually all industrial plant and production facilities
The termSCADA (Supervisory Control and Data Acquisition) usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything from an industrial plant to a nation). Most control actions are performed automatically by RTUs or by PLCs. Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.
Sample SCADA system
How works a nuclear power plant?
what is VFD?A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s speed (RPMs). In other words, the faster the frequency, the faster the RPMs go. If an application does not require an electric motor to run at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor speed requirements change, the VFD can simply turn up or down the motor speed to meet the speed requirement.
What is HMI?
An HMI, or Human-Machine Interface, is a device or software that lets users communicate with a machine or automation system. Besides translating complex data into useable information, an HMI relays the user's commands.By providing information, alerts, commands and other tools, an HMI connects the user with the process being controlled. So the more adapted the tools are to the user, the more appropriately he or she can react.An intuitive, user-friendly HMI can make the difference between an inefficient system and a cost-effective one.Human machine interfaces vary widely, from control panels for nuclear power plants to the screen and input buttons on a cell phone. A human user needs some way to tell the machine what to do, to make requests of the machine, or to adjust the machine. All of these devices can be utilized to send commands to a system or even an interlinked set of systems.
How Does A PLC Operate? There are four basic steps in the operation of all PLCs; Input Scan, Program Scan, Output Scan, and Housekeeping. These steps continually take place in a repeating loop.
1. Input Scan :- Detects the state of all input devices that are connected to the PLC
2.Program Scan :- Executes the user created program logic
3.Output Scan :- Energizes or de-energize all output devices that are connected to the PLC.
4.Housekeeping :-This step includes communications with programming terminals,internal diagnostics .
These steps are continually processed in a loop
What Programming Language Is Used To Program A PLC? While Ladder Logic is the most commonly used PLC programming language, it is not the only one. The following table lists of some of languages that are used to program a PLC.
Ladder Diagram (LD) Traditional ladder logic is graphical programming language. Initially programmed with simple contacts that simulated the opening and closing of relays, Ladder Logic programming has been expanded to include such functions as counters, timers, shift registers, and math operations.
Structured Text (ST) – A high level text language that encourages structured programming. It has a language structure (syntax) that strongly resembles PASCAL and supports a wide range of standard functions and operators. For example;If Speed1 > 100.0 then Flow_Rate: = 50.0 + Offset_A1;Else Flow_Rate: = 100.0; Steam: = ON
Instruction List (IL): A low level “assembler like” language that is based on similar instructions list languages found in a wide range of today’s PLCs.
Sequential Function Chart (SFC) A method of programming complex control systems at a more highly structured level. A SFC program is an overview of the control system, in which the basic building blocks are entire program files. Each program file is created using one of the other types of programming languages. The SFC approach coordinates large, complicated programming tasks into smaller, more manageable tasks.
What is PLC?
A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions based upon a custom program to control the state of output devices. Almost any production line, machine function, or process can be greatly enhanced using this type of control system. However, the biggest benefit in using a PLC is the ability to change and replicate the operation or process while collecting and communicating vital information.