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, an inductor is made of insulated wire wound into a coil.
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, it creates a time-varying magnetic field that induces an electromotive force (e.m.f.) in the conductor, as stated by Faraday's law of induction Lenz's law further explains that the induced voltage opposes the change in current that generated it, leading inductors to resist any fluctuations in current flow.
An inductor typically consists of a coil of insulated copper wire wrapped around a core, which can be 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 standard iron alloys Inductors are available in various shapes, and some feature adjustable cores to modify inductance Additionally, inductors that block very high frequencies may be constructed by threading a ferrite bead onto a wire.
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 similar processes as interconnects, typically employing aluminum in a spiral coil layout However, the limited dimensions restrict the inductance, making the gyrator circuit, which combines a capacitor and active components to mimic inductor behavior, a more common solution Due to their low inductances and minimal power dissipation, on-die inductors are primarily used in high-frequency RF circuits.
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An antenna tuning coil used in an AM radio station exemplifies high power and high Q construction It features single layer winding with spaced turns to minimize proximity effect losses The coil is crafted from silver-plated tubing to decrease skin effect losses and is supported by narrow insulating strips to further reduce dielectric losses.
Air core coils are inductors that lack a ferromagnetic core, utilizing nonmagnetic materials like plastic or ceramic for their construction These coils typically exhibit lower inductance compared to their ferromagnetic counterparts, but they are preferred for high-frequency applications due to the absence of core losses, which tend to increase with frequency However, a potential issue with air core coils is 'microphony,' where mechanical vibrations of the windings can lead to fluctuations in inductance if the windings are not securely supported.
Inductors designed for higher frequencies utilize ferrite cores, which are made from a nonconductive ceramic ferrimagnetic material that prevents the flow of eddy currents The chemical formulation of ferrite is represented as xxFe2O4, where xx indicates different metal compositions Soft ferrites, characterized by low coercivity and minimal hysteresis losses, are specifically employed for inductor cores.
A variety of types of ferrite core inductors and transformers
Ferromagnetic-core inductors utilize a core made from ferromagnetic or ferrimagnetic materials like iron or ferrite to significantly enhance inductance By improving the magnetic field through higher magnetic permeability, these cores can amplify the inductance of a coil by several thousand times.
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 the permeability and the magnetic field increase, resulting in higher inductance Adjustable cores are commonly used in radio applications below 100 MHz to fine-tune inductors, compensating for manufacturing tolerances For frequencies exceeding 100 MHz, cores made from highly conductive non-magnetic materials like aluminum are sometimes utilized, although they reduce inductance as the magnetic field must navigate around them.
Inductors play a crucial role in analog circuits and signal processing, with applications ranging from large inductors in power supplies that, alongside filter capacitors, eliminate ripple from the direct current output, to small inductors like ferrite beads that prevent radio frequency interference in cables They serve as energy storage devices in switched-mode power supplies, supplying energy during "off" periods to maintain current flow and allowing for 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 current 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 composite signal Additionally, tuned circuits are utilized in electronic oscillators to produce 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 may decline due to eddy currents in the core and skin effect in the windings To mitigate this, the core size 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 facilitate switched-mode power supplies that provide isolation between the output and input.
Inductors, often called reactors in electrical transmission systems, play a crucial role in limiting switching and fault currents.
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 portable gadgets.
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 receives its main supply independently for both the armature and field windings A key feature of this motor type is that the armature current does not flow through the field windings, as the field winding is energized by a separate external DC supply This configuration allows for greater control over the motor's performance.
The torque in a separately excited DC motor can be adjusted by altering the field flux (\( \phi \)), regardless of the armature current (\( I_a \)).
Figure 2 1 separately excited DC motor
In this type of motor, the field coil is energized by a dedicated DC voltage supply, while the armature coil receives power from a different source The armature voltage can be variable, but a constant DC voltage is applied to the field coil to induce its operation This electrical separation between the coils is a key characteristic of this motor design.
1.1, Definition of a Separately Excited DC Motor
Direct current motors have been utilized for adjustable speed controllers for over a century and remain the most suitable choice for controlled electrical drives that require a wide range of velocity levels.
The excellent performance features and control properties of these motors are notable; however, a significant drawback is the mechanical commutator, which limits speed and power, increases inertia and axial length, and requires more frequent maintenance compared to other types In contrast, alternating current motors eliminate the commutator and are powered by variable frequency static power converters, though this can lead to higher costs due to their complexity.
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 large machines, the remaining stator is laminated to accommodate rapid variations in torque and speed, particularly when powered by a static power converter that produces significantly distorted currents and voltages.
The basic poles (M and P) are linked to the field windings, which control the field current and generate the main flux across the rotor and stator An armature coil is positioned in the axial slots of the rotor and is connected to commutator bars, with brushes supplying the armature current \(i_a\) This setup produces a distributed ampere-turn (mmf) wave that is stationary in space but rotates in the direction of the quadrature axis, perpendicular to the basic axis, thereby maximizing the output torque generated by the armature current.
When there is a significant distance in the quadrature direction, the armature flux becomes considerably weaker than the basic 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 induced by the armature, effectively eliminating the unwanted armature reaction that could distort the uniform distribution of the main flux across the rotor's circumference.
Figure 2 2 Working Principle of a Separately Excited DC Motor
Compensating coils are primarily used in large machines and converter-fed devices for heavy-duty applications, such as steel mills and traction drives Compensated DC motors can handle higher overloads compared to their uncompensated counterparts, allowing for a rapid increase in armature current Additionally, these motors can tolerate greater current harmonics without negatively affecting commutation, which is crucial when the motor is powered by a static converter.
The commutating poles (C and P) are positioned between the main poles and carry the armature current, playing a crucial role in adjusting the local magnetic field in the neutral zone This adjustment facilitates quick 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 time intervals As the brushes move to the next commutator bars, the feeding points of the winding are switched, leading to the short-circuiting of the commutating winding and an inversion of current Due to the inductance of the windings, which are housed in iron-covered slots, commutation is a continuous process that requires a finite amount of time, thereby limiting the operational speed of the device to prevent 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
Both shunt-wound and separately excited DC motors utilize a regulated voltage to maintain a fixed field current, resulting in similar characteristics for speed, armature current, and torque-armature current In the case of separately excited DC motors, 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, represented as \$E_b / \phi\$ When the load on the motor increases, both back EMF and flux decrease due to the effects of armature resistance and armature reaction However, the reduction in back EMF is more significant than that of the flux, resulting in a slight decrease in the motor's speed as the load increases.
3.2, Torque – Armature Current (Τ – Ia) Characteristics
Torque is directly linked to the flux and armature current, with the flux remaining constant regardless of armature reaction The relationship between torque and armature current (\$T - I_a\$) is linear, starting from the origin This indicates that a significant current is necessary to initiate movement with heavy loads, meaning this type of motor is not suitable for starting 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:
Field control is a method used to regulate the speed of a motor, where reducing the field strength increases the device's speed, while enhancing the field strength results in a decrease in speed This speed regulation is achieved by adjusting the field voltage, which involves changing the voltage in the field circuit while maintaining a constant armature terminal voltage.
PLC Siemens S7-300
PLC
A programmable logic controller (PLC) is a robust industrial computer designed for controlling manufacturing processes, including assembly lines, machines, and robotic devices It offers high reliability, user-friendly programming, and effective process fault diagnosis, making it essential for various industrial applications.
Key features of a programmable logic controller include:
The CPU processes data while input and output (I/O) modules connect the PLC to machinery, supplying the CPU with information and triggering specific outcomes 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.
PLCs must interface with various system types beyond just input and output devices For example, users often need to transfer application data from the PLC to a SCADA (supervisory control and data acquisition) system that oversees multiple connected devices To enable this communication, PLCs offer a variety of communication protocols and ports.
Users need a Human Machine Interface (HMI) to effectively interact 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 information 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 is evident, as they enable operations to function efficiently with little to no manual labor or physical effort required.
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 is essential to consider the total response time of the PLC, as it takes a specific amount of time to react to changes.
A Distributed Control System (DCS) is designed to manage an entire process or plant, integrating multiple Programmable Logic Controllers (PLCs) with a Human-Machine Interface (HMI) This cohesive approach allows for the simultaneous development of all system components, ensuring that the PLC, HMI, alarms, and historian are all aligned and function seamlessly together.
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.
Working 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.
Fault 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.
Memory It consists of memory to store the program It does not consist of memory.
Introduce PLC S7-300 of Siemens
The Siemens Simatic S7-300 is a multi-block PLC featuring a basic processing unit with the option to add standard expansion modules on the right side These external modules consist of functional units that can be customized 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 system expansion Each application determines the number of modules utilized, with at least one being the essential CPU module Additional modules include signal transmission and reception modules for external control, as well as specialized function modules, 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), which are microcomputers that interact with various devices such as factory machines, HMIs, sensors, and end devices These components relay information to computers running SCADA software, which processes, distributes, and visualizes the data for operators and employees to analyze and make critical decisions 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 the SCADA system's timely notifications enable quick resolution and minimize product loss.
Applications of SCADA
SCADA systems play a crucial role in both public and private sector industries by enhancing control, maintaining efficiency, and facilitating data distribution for informed decision-making These systems effectively communicate system issues, helping to reduce downtime Their versatility allows them to be implemented in a variety of enterprises, from simple setups to large, intricate installations, making them the backbone of many 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 at wastewater treatment facilities, and monitoring energy consumption in homes.
Modern SCADA systems, like Ignition, can lead to substantial time and cost savings, as demonstrated by various case studies showcasing their benefits and efficiencies.
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 ).
Intermediate data acquisition stations consist of remote I/O devices, such as Remote Terminal Units (RTUs) or Programmable Logic Controllers (PLCs), equipped with communication capabilities to interface with field-level actuators, including sensors, switch control boxes, and actuator valves.
Communication system: includes industrial communication networks, telecommunications equipment and multiplexing converters that transmit field-level data 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
Water treatment plants and facilities can enhance their efficiency by ensuring their monitoring equipment is current and precise Although traditional SCADA (supervisory control and data acquisition) systems are widely used, the newer cloud-based SCADA systems are emerging as a more reliable and effective solution.
A cloud-based SCADA system empowers water management plants to monitor chemical and toxin levels while providing precise, accessible records from any location This advancement allows managers and operators to retrieve data remotely using their satellite or Wi-Fi-enabled devices, moving beyond the limitations of fixed digital read-outs on the SCADA unit.
In the study on contaminated water, the EPA aimed to address the issues while developing stricter regulations Americans prioritize access to safe drinking water and are frustrated by the slow bureaucratic process of establishing these essential guidelines.
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 contaminants being regulated in the past twenty years, highlighting the challenges faced in achieving effective water safety measures.
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 is leveraging digital tools to enhance efficiency and speed in their work By analyzing data points, they aim to gain precise insights that can facilitate quicker results and prompt actions.
Our rapid industrial advancements are causing significant environmental changes that outpace our understanding Fortunately, technological progress allows us to leverage digital tools, such as cloud-based SCADA solutions, to effectively monitor, record, and enhance research for environmental improvements.
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 performance By optimizing the supply chain, it minimizes inefficiencies, reduces waste, and ensures proper equipment maintenance.
Oil and gas SCADA software empowers operators to effectively monitor pipeline and gas well production, ensuring timely automatic notifications and alerts for any issues This enhancement in performance allows the oil and gas industry to stay competitive by optimizing resources and processes.
The oil and gas industry poses significant environmental risks and safety concerns, as leaks and spills can lead to costly damages and severe ecological harm 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 improving operational efficiency.
SCADA systems enhance the speed of issue resolution by providing operators with immediate notifications of malfunctions through mobile device integration This rapid response capability not only ensures public safety but also upholds 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 significant risks Early awareness by maintenance workers allows first responders to arrive promptly and prepared, potentially saving both time and lives SCADA systems play a vital role in the oil and gas industry by minimizing downtime, providing essential information to management, and reducing risks These systems monitor telecommunication networks and physical wellheads for upstream applications, with RTUs detecting adverse conditions at communication towers or remote well pads If a pump faces extreme heat or pressure loss, regional or field office managers are alerted before a failure occurs, thereby mitigating financial losses associated with downtime.
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 to address potential issues before they escalate, thereby averting dangerous blowouts and spills Investing in SCADA equipment ensures long-lasting safety for valuable assets and offers peace of mind for operators.
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
In times of machinery failure, SCADA systems play a vital role in crisis response by allowing management to address issues promptly This immediate action not only reduces the risk of environmental disasters but also ensures the safety of workers.
SCADA systems collect crucial data, enabling companies to analyze information thoroughly, implement strategic responses promptly, and accurately forecast trends.
Supervision from a distance is made possible by SCADA, allowing machinery to be controlled remotely, even in remote geographic areas with limited manpower This technology facilitates effective communication between remote equipment and the control center.
Funtionalities of PLCs in a SCADA
Figure 4 7 Funtionalities of PLC in a SCADA
A PLC is a crucial hardware component that monitors inputs and outputs, collects essential system data, and processes multiple data points.
A PLC serves as the essential wiring that empowers the intelligence of a SCADA system, functioning like a brain When effectively programmed, a PLC can manage intricate operations within an industrial control system with high efficiency.
Programmable logic controllers (PLCs) are essential for manufacturing process control, as they receive data from input devices and sensors, process this information, and 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 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 the necessary control and monitoring functions in real-time Subsequently, the SCADA software relays this information back through the PLC.
The market is filled with various PLC brands, but their quality and functionality can vary significantly Some clients continue to use certain brands due to their established presence in older systems, while others prefer brands that provide enhanced features and capabilities.
A successful control system design must consider the performance requirements of the PLC to ensure optimal functionality Additionally, it is crucial that the SCADA software is compatible with the installed PLC, as this compatibility guarantees efficient operations, 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