Distinguish conductor and inductor...7 Chapter 2: Electrical motors...9 1, a Separately Excited DC Motor...9 1.1, Definition of a Separately Excited DC Motor...9 1.2, Working Principle o
Introduction to inductor
Definition
An inductor, often referred to as a coil, choke, or reactor, is a passive electrical component with two terminals that stores energy in a magnetic field when current passes through it Typically made of insulated wire wound into a coil, inductors play a crucial role in various electrical circuits.
An inductor is defined by its inductance, which measures the relationship between voltage and the rate of change of current The standard unit of inductance in the International System of Units (SI) is the henry (H), named after the 19th-century American scientist Joseph Henry.
When the current in a coil changes, a time-varying magnetic field induces an electromotive force (e.m.f.) in the conductor, as explained by Faraday's law of induction Lenz's law states that this induced voltage has a polarity that opposes the current change that produced it, causing inductors to resist any fluctuations in current.
An inductor typically comprises a coil of insulated copper wire, which can be wrapped around a core made of plastic for air-core inductors or ferromagnetic material for iron-core inductors The ferromagnetic core enhances the magnetic field and increases inductance due to its high permeability Low-frequency inductors are designed similarly to transformers, utilizing laminated electrical steel cores to minimize eddy currents For applications above audio frequencies, 'soft' ferrites are preferred as they reduce energy losses compared to conventional iron alloys Inductors are available in various shapes, with some featuring adjustable cores to modify inductance, while others, designed to block very high frequencies, may incorporate ferrite beads strung on wires.
Small inductors can be directly etched onto printed circuit boards in a spiral pattern, often utilizing a planar core Integrated circuits can also incorporate small value inductors using processes similar to interconnect fabrication, typically employing aluminum in a spiral coil layout However, the limited dimensions of these inductors restrict their inductance, leading to the common use of a gyrator circuit that combines a capacitor and active components to mimic inductive behavior Due to their low inductances and minimal power dissipation, on-die inductors are primarily utilized in high-frequency RF circuits.
An antenna tuning coil used in an AM radio station exemplifies a high power, high Q design It features a single layer winding with spaced turns to minimize proximity effect losses Constructed from silver-plated tubing, it effectively reduces skin effect losses Additionally, narrow insulating strips support the coil, further decreasing dielectric losses.
Air core coils are inductors that utilize nonmagnetic materials, such as plastic or ceramic, instead of ferromagnetic cores While they typically exhibit lower inductance compared to their ferromagnetic counterparts, air core coils are preferred for high-frequency applications due to their immunity to core losses, which escalate with frequency However, a potential drawback of air core coils is 'microphony,' where mechanical vibrations of unsupported windings can lead to fluctuations in inductance.
Inductors designed for higher frequencies utilize ferrite cores, which are made from a nonconductive ceramic ferrimagnetic material This unique property prevents the flow of eddy currents within the ferrite, enhancing efficiency The chemical composition of ferrite is represented as xxFe2O4, where "xx" indicates different metallic elements Soft ferrites, characterized by their low coercivity, are preferred for inductor cores due to their minimal hysteresis losses.
A variety of types of ferrite core inductors and transformers
Ferromagnetic-core inductors, also known as iron-core inductors, utilize a core made from ferromagnetic or ferrimagnetic materials like iron or ferrite to significantly enhance inductance By incorporating a magnetic core, these inductors can boost the inductance of a coil by several thousand times, thanks to the core's superior magnetic permeability, which amplifies the magnetic field.
The most prevalent type of variable inductor features a movable ferrite magnetic core that can be adjusted within the coil By inserting the core deeper into the coil, both permeability and inductance increase due to a stronger magnetic field In radio applications, particularly those operating below 100 MHz, adjustable cores are essential for tuning inductors to precise values, compensating for manufacturing tolerances For frequencies exceeding 100 MHz, cores made from highly conductive non-magnetic materials like aluminum are sometimes used, although these can reduce inductance as the magnetic field must navigate around them.
Inductors play a crucial role in analog circuits and signal processing, serving various applications from large inductors in power supplies that, alongside filter capacitors, eliminate ripple from the direct current output, to small ferrite beads or toroids that mitigate radio frequency interference in cables They act as energy storage devices in switched-mode power supplies, supplying energy during "off" periods to maintain current flow and facilitating configurations where the output voltage exceeds the input voltage.
A tuned circuit, made up of an inductor and a capacitor, serves as a resonator for oscillating currents These circuits are essential in radio frequency equipment, including radio transmitters and receivers, where they function as narrow bandpass filters to isolate a specific frequency from a mixed signal Additionally, tuned circuits play a crucial role in electronic oscillators for generating sinusoidal signals.
Transformers, essential components of electric utility power grids, consist of two or more inductors with coupled magnetic flux, known as mutual inductance As frequency increases, transformer efficiency can decline due to eddy currents in the core and skin effect in the windings To mitigate this, core sizes can be reduced at higher frequencies, which is why aircraft utilize 400 hertz alternating current instead of the standard 50 or 60 hertz, resulting in significant weight savings from smaller transformers Additionally, transformers play a crucial role in switched-mode power supplies by isolating the output from the input.
Inductors, commonly known as reactors in electrical transmission systems, play a crucial role in limiting switching and fault currents Their application ensures the stability and safety of electrical networks.
Inductors exhibit parasitic effects that lead to deviations from their ideal performance, contributing to electromagnetic interference (EMI) Their physical dimensions hinder integration with semiconductor chips, resulting in a decreasing reliance on inductors in contemporary electronic devices, especially in compact and portable technologies.
7 inductors are increasingly being replaced by active circuits such as the gyrator which can synthesize inductance using capacitors.
Electrical motors
A separately excited DC motor operates with independent power supplies for both the armature and field windings Unlike other DC motors, the armature current does not flow through the field windings, as the field winding receives its power from a distinct external DC source This unique configuration influences the torque characteristics of the motor.
The torque in a separately excited DC motor can be adjusted by altering the field flux (φ), regardless of the armature current (Ia).
Figure 2 1 separately excited DC motor
In this motor design, the field coil is energized by a dedicated DC voltage supply, while the armature coil receives power from a separate source Although the armature voltage can be variable, a consistent DC voltage is applied to the field coil to create the necessary magnetic field This electrical separation between the coils is a key characteristic of this type of motor.
1.1, Definition of a Separately Excited DC Motor
For over a century, direct current motors have been utilized in adjustable speed controllers, making them the most suitable choice for applications requiring controlled electrical drives across a wide range of velocities.
Electric motors are favored for their outstanding performance and control capabilities; however, a significant drawback is the mechanical commutator, which can limit speed and power, increase inertia, and require more frequent maintenance compared to other motor types In contrast, alternating current motors eliminate the need for a commutator by utilizing variable frequency static power converters, although this complexity can lead to higher costs.
This is one of the main reasons why new AC controllers could not quickly supplant DC types, once the semiconductor technology had significantly improved.
The principle of a DC motor performing in steady-state is assumed to be known, but let us discuss some basic facts below.
1.2, Working Principle of a Separately Excited DC Motor
The schematic cross-section of a two-pole DC motor illustrates the fixed stator (S) and the cylindrical rotor, known as the armature (A) To minimize iron losses from fluctuating magnetic flux, the rotor and pole shoes are consistently connected In larger machines, the remainder of the stator is laminated to enhance performance under rapidly changing torque and speed conditions, particularly when powered by a static power converter that generates significantly distorted currents and voltages.
The basic poles (M and P) are linked to the field windings, which drive the field current and establish the main flux across the rotor and stator An armature coil, enclosed in the rotor's axial slots and connected to commutator bars, generates the armature current (ia) through brushes and the commutator This setup produces a distributed ampere-turn (mmf) wave that remains fixed in space while rotating in the direction of the quadrature axis, perpendicular to the basic axis, thereby maximizing output torque for the armature current.
When there is a significant distance in the quadrature direction, the armature flux becomes considerably weaker than the fundamental flux This flux can be further reduced by installing compensating coils in the axial slots of the pole shoes and connecting them in series with the armature These opposing ampere-turns counteract the quadrature field generated by the armature, effectively eliminating the unwanted armature reaction that could distort the uniform distribution of the main flux beneath the poles around the rotor's circumference.
Figure 2 2 Working Principle of a Separately Excited DC Motor
Compensating coils are primarily utilized in large machinery and converter-fed devices for heavy-duty applications, such as steel mills and traction drives These compensated DC motors can handle higher overloads compared to their uncompensated counterparts, allowing for a rapid increase in armature current Additionally, they can manage greater current harmonics without negatively affecting commutation, which is crucial for preventing brush sparking, especially when the motor is powered by a static converter.
Commutating poles (C and P) are positioned between the main poles and conduct the armature current, playing a crucial role in adjusting the magnetic field at the neutral point This adjustment facilitates rapid and spark-free commutation by generating a suitable voltage in the armature coil, which is temporarily diminished by the brushes.
The principle of commutation in a two-pole DC motor involves the closed armature section and the positioning of brushes at two consecutive moments As the brushes move to the next commutator bars, the feeding points of the winding are switched, leading to the immediate short-circuiting of the commutating winding while simultaneously inverting the current.
Each winding, encased in iron-covered slots, generates inductance, resulting in a continuous commutation process that requires a finite amount of time This limitation affects the device's operational speed, preventing excessive sparking of the brushes.
2, Equations of Voltage, Current, and Power for a Separately Excited DC Motor
In a separately excited DC motor, field and armature windings are excited to form two various DC supply voltages In this motor, we have
Armature current I = Line current = I = Ia l
Back emf developed: where V is the main voltage and Ra is the armature resistance.
Power is drawn from the main source:
Mechanical power developed (Pm) = Power input to the armature – power wasted in the armature
3, Operating Characteristics of a Separately Excited DC Motor
In both shunt-wound and separately excited DC motors, the field is supplied with a regulated voltage, resulting in a fixed field current Consequently, these motor types exhibit the same characteristics regarding speed, armature current, and torque–armature current Additionally, in a separately excited DC motor, the magnetic flux is considered constant.
3.1,Speed – Armature Current (N – Ia) Characteristics
The speed of a motor is influenced by the relationship between back EMF and flux (Eb/φ) When the load on the motor increases, both back EMF and flux decrease due to reductions in armature resistance and armature reaction However, back EMF decreases more significantly than flux, resulting in a slight drop in the motor's speed under load conditions.
3.2, Torque – Armature Current (Τ – Ia) Characteristics
Torque in this context is directly associated with flux and armature current, where the flux remains constant irrespective of armature reaction The relationship between torque and armature current (Ia) is represented by a straight line originating from the origin This indicates that substantial current is necessary to initiate movement under heavy loads, highlighting that this type of motor is not designed to start under such conditions.
4, Speed Control of a Separately Excited DC Motor
The speed of this type of DC motor is determined by the following methods:
PLC Siemens S7-300
PLC
A programmable logic controller (PLC) is a robust industrial computer designed to control manufacturing processes, including assembly lines, machinery, and robotic systems It offers high reliability, user-friendly programming, and effective fault diagnosis, making it essential for various industrial applications.
Key features of a programmable logic controller include:
The CPU processes data while I/O modules connect the PLC to machinery, providing essential information and triggering specific results These I/O modules can be either analog or digital, and they can be mixed and matched to create the optimal configuration for various applications.
In addition to input and output devices, PLCs must interface with various system types, such as SCADA (supervisory control and data acquisition) systems, which monitor multiple connected devices To enable this integration, PLCs offer a range of communication protocols and ports, ensuring seamless data export and communication with other systems.
A Human Machine Interface (HMI) is essential for users to interact effectively with a Programmable Logic Controller (PLC) These operator interfaces can range from large touchscreen panels to basic displays, enabling users to input and monitor PLC data in real-time.
In industrial automation, PLC performs a wide variety of manufacturing production, monitoring machine tool or equipment, building the system, and process control functions.
For the electrical power system analysis, PLC plays operation for maintenance and other main roles in the power plants and the smart grid system.
The rise of Programmable Logic Controllers (PLC) in commercial control applications highlights their ability to streamline operations, allowing tasks to be performed with minimal manpower and reduced physical effort.
For the domestic purpose, PLC act as a remote operating device or automatic sensing device We can automate some day-to-day activities with PLC.
Automation Industries where PLC is needed: Steel Industry, Glass Industry, Paper industry, Textile industry, Cement Industry, Chemical industry,
Automobile industry, Food Processing System, Oil and Gas Power Plant, Wind Turbine System, Robotic Automation System, Underground Coal Mine and many more industries…
When selecting a PLC for applications where speed is critical, it's essential to consider the total response time of the PLC, as it determines how quickly the system reacts to changes.
A Distributed Control System (DCS) is designed to manage entire processes or plants by integrating multiple Programmable Logic Controllers (PLCs) with a Human-Machine Interface (HMI) This holistic approach enables integrators to develop all components of the DCS simultaneously, ensuring seamless functionality across the system, rather than sequentially building each element like PLCs, HMIs, alarms, and historians.
Differences between PLC and relays
(PLC) is a solid-state computerized industrial controller that performs software logic by using input
& output modules, CPU, memory, and others.
Relay is an electro-mechanical switching hardware device (Hardware Switching Device).
PLC plays a monitoring as well as controlling role in designing circuits.
Relay plays only a controlling role in the designing circuit. Monitoring is not so easy with a relay.
In the PLC, we can write the program using different types of programming languages.
In the Relay, we cannot write the program.
Function PLC consists of more programming functions like timer, counter, memory, etc.
Relay gives only one fault detection function And it does not have much-advanced functionalities.
Design You can easily modify the designing circuit.
Modification of the electronic circuit is more difficult as compared to PLC.
PLC has more capabilities of input and output modules.
The relay does not have more capabilities.
PLC provides more flexibility than the relay.
The relay provides less flexibility.
You can easily find the fault by using the software.
It is very hard to find fault in the Relay circuit.
PLC has a time response of nearly 50 msec and above.
Relays have less than 10 msec response time.
It consists of memory to store the program.
It does not consist of memory.
Introduce PLC S7-300 of Siemens
The Siemens S7-300 PLC, part of the Simatic family, is a versatile multi-block programmable logic controller Its fundamental design features a basic processing unit, which can be enhanced with various standard expansion modules on the right side These external modules include functional units that can be tailored to meet specific engineering requirements.
Figure 3 5 CPU front face shape
The PLC S7-300 features a modular design that allows for versatile applications and facilitates the creation of compact systems while simplifying expansion Each application dictates the number of modules used, with at least one CPU module required Additional modules include signal transmission and reception modules, specialized function modules, and are collectively referred to as expansion modules.
The module expands the input/output (SM) port, including: DI, DO, DI/DO, AI, AO, AI/AO.
Separate control function module (FM).
Start up and create a new project
Run simulation program: PLC-SIM
Graph the program to the PLC SIM
Run simulation to see the results
In fact, PLC S7-300 is used in a variety of applications, such as: Controlling industrial robots, clean water treatment lines, controlling servo motor systems or tool-making machines v.v
SCADA
Supervisory Control And Data Acquisition (SCADA)
Supervisory control and data acquisition (SCADA) is a system of software and hardware elements that allows industrial organizations to:
Control industrial processes locally or at remote locations
Monitor, gather, and process real-time data
Directly interact with devices such as sensors, valves, pumps, motors, and more through human-machine interface (HMI) software
Record events into a log file
SCADA systems are crucial for industrial organizations since they help to maintain efficiency, process data for smarter decisions, and communicate system issues to help mitigate downtime.
The fundamental SCADA architecture relies on programmable logic controllers (PLCs) and remote terminal units (RTUs) to communicate with various devices like factory machines, sensors, and HMIs These microcomputers relay information to SCADA software, which processes and displays the data, enabling operators to analyze it for critical decision-making For instance, when a SCADA system detects a high error rate in a product batch, it alerts the operator, who can then pause operations and investigate the issue through the HMI Upon reviewing the data, the operator identifies a malfunction in Machine 4, demonstrating how SCADA systems facilitate prompt issue resolution and minimize product loss.
Applications of SCADA
SCADA systems play a crucial role in both public and private sectors by enabling industrial organizations to optimize efficiency, facilitate data distribution for informed decision-making, and promptly address system issues to reduce downtime Their versatility allows SCADA systems to be implemented in various enterprises, from straightforward setups to intricate installations, making them the backbone of numerous modern industries.
SCADA systems are integral to modern infrastructure, operating behind the scenes in various applications such as managing refrigeration in supermarkets, ensuring safety and efficiency in refineries, maintaining quality in wastewater treatment plants, and monitoring energy consumption in homes.
Implementing an effective SCADA system can lead to substantial time and cost savings Various case studies demonstrate the advantages and financial benefits associated with utilizing modern SCADA software solutions like Ignition.
SCADA systems
The structure of a SCADA system has the following basic components :
Central monitoring control station: is one or more central servers ( central host computer server ).
An intermediate data acquisition station consists of remote I/O devices, such as RTUs or PLCs, equipped with communication functions to interface with actuators like field-level sensors, switch control boxes, and actuator valves This system relies on industrial communication networks, telecommunications equipment, and multiplexing converters to effectively transmit data from the field level to control units and servers.
Human-machine interface HMI ( Human-Machine I nterface ) : Are devices that display data processing for the operator to control the system's operations.
Systems using Scada
Figure 4 4 Municipal water supply and sewage treatment
To enhance efficiency in water treatment plants and usage facilities, it's essential to ensure that monitoring equipment is current and precise While traditional SCADA (supervisory control and data acquisition) systems are widely used, the emergence of cloud-based SCADA systems offers a more reliable and advanced solution for modern operations.
A cloud-based SCADA system empowers water management plants to monitor chemical and toxin levels while providing precise, accessible records from any location This technology eliminates the limitations of fixed digital read-outs, allowing managers and operators to access critical data through their satellite or Wi-Fi-enabled devices.
The EPA is working to address the impacts of contaminated water while developing stricter regulations Americans are eager for prompt action to ensure access to safe drinking water, rather than getting caught up in bureaucratic delays.
Congress requires the EPA to demonstrate a significant opportunity for public health improvement before implementing new regulations on water utilities This lengthy and complex process has resulted in no new contaminant regulations in the past two decades, highlighting the challenges officials face in addressing water quality issues effectively.
Another benefit of a cloud-based SCADA system is that data collected in real- time from the contaminated areas can be studied, compared, and shared with
A team of 25 researchers utilizes a faster and more efficient digital approach to analyze data points, enabling them to obtain the most accurate insights This method aims to facilitate quicker results and prompt actions based on their findings.
Due to rapid industrial advancements, environmental changes are occurring at an unprecedented pace Fortunately, technological innovations, such as cloud-based SCADA solutions, enable us to effectively monitor, record, and enhance research efforts aimed at improving our understanding of these changes.
4.2 Oil and Gas SCADA Efficiency Benefits
Figure 4 5 Oil and Gas systems
SCADA significantly enhances the efficiency of processes in the oil and gas industry by enabling close monitoring of operations By optimizing the supply chain, it minimizes inefficiencies, reduces waste, and ensures proper maintenance of equipment, ultimately leading to improved performance.
Oil and gas SCADA software empowers operators to effectively monitor pipeline and gas well production, ensuring prompt detection of issues through automatic notifications and alerts This enhanced performance allows the oil and gas industry to optimize resources and processes, maintaining a competitive edge in the market.
The oil and gas industry poses significant environmental risks and safety hazards, with leaks and spills causing substantial ecological damage and financial burdens Implementing stringent environmental standards is essential for both the distribution and production processes A SCADA monitoring system enhances safety by providing advanced alarm notifications and efficient oversight.
SCADA systems enhance the speed of issue resolution by providing operators with real-time notifications on their mobile devices when a malfunction occurs This rapid response capability not only ensures public safety but also helps uphold environmental protection standards.
The Three Oil and Gas SCADA Applications
RTUs are effective for monitoring downstream conditions at a refinery This encompasses a significant footprint Time is required due to the complex nature and size of the sites
Monitoring temperatures in holding tanks is crucial, as elevated levels can pose serious risks SCADA systems play a vital role in the oil and gas industry by ensuring timely responses from maintenance workers and first responders, ultimately saving both time and lives These systems provide essential data that helps prevent downtime, enhances management decision-making, and mitigates risks By continuously monitoring telecommunication networks and wellheads, SCADA can detect adverse conditions at remote sites through RTUs This proactive approach alerts regional or field office managers to potential threats, such as extreme heat or pressure loss in pumps, allowing for timely interventions that significantly reduce financial losses associated with operational disruptions.
RTUs play a crucial role in midstream applications, particularly in pipelining, by monitoring flow rates to prevent overpressure and mitigate leak risks They provide timely information, allowing managers to address issues before they escalate, thus averting hazardous blowouts and spills Investing in SCADA equipment ensures long-lasting safety for valuable assets, offering peace of mind and durability for years to come.
The Main Benefits of SCADA
SCADA provides numerous benefits to companies in the gas and oil sector at every operational level These benefits are detailed below
Reducing Errors: Human error is eliminated through the automation support of SCADA This offers the precision necessary for improving efficiency and effectively decreasing expensive downtime risks
SCADA systems play a vital role in crisis response during machinery failures, allowing management to address issues promptly This immediate action not only reduces the potential for environmental disasters but also ensures the safety of workers on site.
SCADA systems collect crucial data, enabling companies to analyze information thoroughly, implement strategic responses promptly, and accurately predict trends.
Supervision from a distance is made possible through SCADA systems, enabling the control and monitoring of machinery in remote geographic areas with limited manpower This technology facilitates effective communication between remote equipment and the central control center, ensuring efficient operations.
Funtionalities of PLCs in a SCADA
Figure 4 7 Funtionalities of PLC in a SCADA
A Programmable Logic Controller (PLC) is a crucial hardware component that monitors inputs and outputs, collects essential system data, and processes multiple data points efficiently.
SCADA functions like the brain of an industrial control system, while a PLC serves as the wiring that facilitates its intelligence When programmed effectively, a PLC can manage intricate operations with high efficiency.
A programmable logic controller (PLC) processes data from connected input devices and sensors to activate outputs based on pre-set parameters According to Motion Control Online, PLCs are capable of monitoring and recording runtime data, making them robust and flexible solutions for manufacturing process control that can adapt to a wide range of applications.
A PLC and SCADA system are both necessary for a control system to operate.
As the core intelligence platform of an industrial system, SCADA relies on the data performance duties of PLCs to function.
PLCs facilitate the exchange of data with SCADA software, which assesses real-time control and monitoring requirements Subsequently, SCADA sends the necessary information back through the PLC for efficient operations.
The market is flooded with various PLC brands, but their quality and functionality vary significantly While some clients continue to use certain brands due to their historical integration in older systems, others choose more advanced options that provide enhanced features and capabilities.
When designing a control system, it is crucial to consider the performance requirements of the PLC to ensure optimal functionality Additionally, ensuring compatibility between the SCADA software and the installed PLC is essential for efficient operation, ultimately saving clients both time and money.
Compare DCS and SCADA
It used in factories and located within a more limited area It used by private companies and PSU which covers large geographical areas
A significant amount of closed loop control is present on the system
Closed loop control is not a high priority in it
It is process oriented and control of the process as its main task
It is data gathering oriented where control center and operator are its focus
More controllers used to implement advance process control technique Many RTU and PLC for collection of data This can not carry out advance process control
Its always connected to its data source.
So, it doesn’t need to maintain a database of current values
It needs to maintain database of last known good values for prompt operator display
Redudancy is usually handled by parallel equipment
Redundancy is usually handled in a distributed manner
Figure 4 9 Supervisory Control And Data Acquisition