PLC – Programmable Logic Controller
A PLC is an industrial-grade digital computer designed to perform control functions—especially for industrial applications.
The majority of PLCs today are modular, allowing the user to add an assortment of functionality including discrete control, analog control, PID control, position control, motor control, serial communication, and high-speed networking. Compared to older technologies, the PLC is easier to troubleshoot, more reliable, more cost-effective, and far more versatile.
Modicon, shortened from modular digital controller, is both the name of the first PLC product and the brand that invented it. Below is a picture of a Modicon PLC.
HMI – Human Machine Interface
A human-machine interface (HMI) is the user interface that connects an operator to the PLC for an industrial system.
Industrial control systems are integrated hardware and software designed to monitor and control the operation of machinery and associated devices in industrial environments, including those that are designated critical infrastructure. An HMI includes electronic components for signalling and controlling automation systems.
Some HMIs also translate data from industrial control systems into human-readable visual representations of the systems. Through the HMI, an operator can see schematics of the systems and turn switches and pumps on or off, for example, or raise or lower temperatures. HMIs are usually deployed on Windows-based machines, communicating with programmable logic controllers (PLC) and other industrial controllers.
The accessibility of HMIs poses a risk for ICS security. The systems themselves have long been considered secure from malware because they were not connected to the Internet. In some cases, administrators have deliberately disabled security mechanisms.
VSD – Variable Speed Drive
Variable Speed Drives (VSDs) control the speed of motors, fans and pumps – matching their speed and torque to the requirements of the application and in most cases delivering considerable savings in electricity used.
In technical terms, VSDs convert the incoming electrical supply of fixed frequency and voltage into a variable frequency and variable voltage output to the motor with a corresponding change in the motor speed and torque.
The VSD manages the motor’s speed from zero rpm through to typically 100-120% of its full rated speed whilst up to 150% rated torque can be achieved at reduced speed.
Energy Savings with VSDs
Using a Variable Speed Drive to slow a fan or pump motor from 100% to 80% can save as much as 50% of the energy used
Every fan, pump or HVAC motor needs a VSD – dramatically reducing the electricity used to match the real need rather than running at full speed
The Carbon Trust recognises the benefits that Variable Speed Drives offer in the challenge to reduce electricity used, electricity costs and carbon emissions:
Reducing the speed and torque of the motor to more closely match the environment and requirements of the process, rather than running at full speed all the time – reduces the amount of electricity being used. This reduction in speed relates directly to a reduction in power and energy.
Variable Speed Drives offer significant savings in electricity consumed and can be applied in a variety of applications. A detailed site survey will determine the right application and expected energy savings.
Sounds simple – and they are…simple and effective
Servos (Drives and Controllers)
A servo drive is a special electronic amplifier used to power electric servomechanisms: its main task is to monitor the feedback signal from the servomechanism and continually adjusts for deviation from expected behavior. In this post, we’ll try to briefly summarize what it is and how it works.
The first time we should do to properly understand such topic is to look at some servo drive basics. A servo system is made up of four components including a servo motor and drive, a controller, and a feedback device. Often, the feedback device is an encoder. The controller is programmed to instruct the motor on what it must do which then triggers the drive to send sufficient electrical energy to the motor to make the required action possible.
The controller in the system is responsible for calculating the path (trajectory) needed to send a low-voltage command signal to the drive. The drive is then responsible for sending the required voltage and current to the motor which enables it to achieve the desired motion.
A servo drive is capable of controlling the torque, velocity or position. In a servo system, the servo drive typically controls the torque.
You may also hear a servo drive being called an amplifier. It’s easy to see why as the servo drive takes the control signal from the controller to amplify it to the required voltage and current before sending it to the motor.
How Does a Servo Drive Work?
There are several types of servo drives that all serve slightly different purposes. The most common type of servo drive is a torque-mode amplifier. This servo drive converts the command signal from the controller into a specified current and sends it to the motor. The Servo drive is controlling the amount of torque that the motor can produce.
A linear servo drive works slightly differently because the current is proportional to the force rather than the torque. This directly drives the motor’s force output.
There are many types of servo drives which are classified based on their application such as the AC servo motor and DC servo motor. To distinguish between the different types of servo drives there are some considerations to be had. Is the current type AC or DC? What type of communication is being used? Does the motor use brushes? Is the motor’s rotating field synchronous or asynchronous?
AC or DC are the most basic classifications for servo drives. The main difference between the two is the ability to control speed. A DC motor is characterized by the speed being directly proportional to the supply voltage with a constant load. Whereas, an AC motor the speed is determined by the frequency of the applied voltage and the number of magnetic poles.
An AC servo motor will withstand a higher current compared to DC servo motor which is why an AC servo motor is the most commonly produced by servo drive manufactures for assembly line robotics in the manufacturing industry or any other application that requires high intensity skilled and precision work.
What is a Servo Drive Controller?
Servo drive controllers are used to control servomotors in a servo system. The controller acts as the brains. It moves information from the feedback device and sends the necessary voltage signals to the drive. The nervous system in this analogy is the drive. The drive sends the required amount of current to the motor. This is an ongoing process of reading and responding to the feedback which created a closed-loop system. This is the defining feature of a servo system allowing it to improve the transient response times, reduce any steady-state errors, and reduce the sensitivity of the system to load parameters
SCADA (Supervisory Control and data aquisition)
What is SCADA? The SCADA acronym stands for Supervisory Control and Data Acquisition. When considering this term, you can conjure varying images and you should.
A SCADA system is a collection of both software and hardware components that allow supervision and control of plants, both locally and remotely.
What is SCADA? The SCADA acronym stands for Supervisory Control and Data Acquisition. When considering this term, you can conjure varying images and you should.
A SCADA system is a collection of both software and hardware components that allow supervision and control of plants, both locally and remotely.
The SCADA also examines, collects, and processes data in real time.
Human Machine Interface software facilitates interaction with field devices such as pumps, valves, motors, sensors, etc.
Also within the SCADA software is the ability to log data for historical purposes.
The structural design of a standard SCADA system starts with Remote Terminal Units and/or Programmable Logic Controllers.
As you know, RTUs and PLCs are microprocessors that communicate and interact with field devices such as valves, pumps, and HMIs.
That communication data is routed from the processors to the SCADA computers, where the software interprets and displays the data allowing for operators to analyze and react to system events.
Before SCADA, plant personnel had to monitor and control industrial processes via selector switches, push buttons, and dials for analog signals.
This meant that plants had to maintain personnel on site, during production, in order to control the processes.
As manufacturing grew and sites became more remote in nature, relays and timers were used to assist in the supervision and control of processes. With these devices employed, fewer plant personnel were required to be on site in order to oversee and control operations.
While relays and timers did provide some level of automation, the panels required for these devices took up valuable real estate, troubleshooting was a nightmare, and reconfiguring was difficult at best.
These issues, in conjunction with the need to grow even larger industrial plants, helped to facilitate the birth of automation.