here is some details about automation of electrical & electronics , Sensor, Drives,Timer
AUTOMATION IN ELECTRICAL & ELECTRONICS
A Summer Training Report
Bachelor of Technology
in ELECTRICAL ENGINEERING
Submitted by: YOGESH.R
IV YEAR , EE
Supervisor: Mr. R.K. KUMAWAT
Associate Lecture of Electrical
DEPARTMENT OF ELECTRICAL ENGINEERING Mewar University, NH - 79 Gangrar, Chittorgarh (Rajasthan) – 312901
This is to certify that the Report titled “ Automation in Electrical & Electronics ” was prepared and presented by YOGESH.R (10MUBEE136) of Mewar University, Chittorgarh in partial fulfilment of the requirement as a part of curriculum under the Mewar University, Chittorgarh during the B.Tech program in the session 2013 - 2014
Mr. S.K.Singh HOD (EE)
I YOGESH.R, IV Year VII Semester B.Tech. (E.E.), student of Mewar
University, Chittorgarh do hereby declare that the Training report entitled “Automation in Electrical and Electronics” is the original work carried out by me under the supervision of Mr R. K. Kumawat towards partial fulfillment of the requirement of B.Tech. Degree.
YOGESH.R B. Tech Final Year Electrical Engineering
I am very pleased to express my deep sense of gratitude to my esteem guide “Mr. Prabhakar” for his valuable training, encouragement and facilities provided during the Training Work. There were umpteen moments when I learned heavily from him. It is the fact, without his construction and simulating criticism arduous but invaluable advice sought time to time, masterly guidance deep personal interest and attention, this work would not have seen the down of the day and could never have attend the present stage. I am also heartily thanks to Mr. Ashok Gadiya(Honorable,Chancellor), Mr. Harish Gurnani(Director, Training and placement), Mr. S. K. Singh (HOD, Department of EE) and all faculty members for their co-operation . I extend my sincere thanks to my friends who were there with me directly or in directly during the Work. YOGESH.R B.Tech, IV year Electrical Engineering PLACE : Mewar University DATE : 07-09-13
Automation devices such as controllers and data systems and/or services. Systems and methods are provided that receive statements or other unit of data interaction from an automation device, provide the statements to an appropriate system or service for processing, and optionally return a response such as a result set. An Automation in electrical and electronics or Automatic controller is a soft and hard computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. Automation are used in many industries and machines. An electrical switch is any device used to interrupt the flow of electrons in a circuit.A sensor (also called detector) is a converter that measures a physical quantity and converts it into a signal which can be read by an observer or by an (today mostly electronic) instrument. Sensors is an important component in closed loop automation system. Timer is an effective tool in each and every industry. They keep beat of an enterprise or an industry in synchrony.A timer provides a way to perform a delayed action or a periodic action. The timer waits until a certain time interval has elapsed and then fires, sending a specified message to a specified object. For example, you could create a timer that sends a message to a controller object, telling it to update a particular value after a certain time interval.
S. No TITLE CERTIFICATE DECLARATION AKNOWNLEGMENT ABSTRACT PAGE.NO
ii iii iv 1-4 1 1 4 5 - 13 5 5 6 8 9 9 10 10 11 11
1.1 1.2 1.3 Introduction Significance of automation Application of automation
2.1 2.2 2.3
Introduction Criteria to choose a sensor Classification of sensor Temperature sensor 2.4.1. 2.4.2. 2.4.3. Thermocouple RTD Thermistor
Proximity sensor Different types of proximity sensor 2.6.1. inductive sensor
CHAPTER 1 AUTOMATION
Industrial automation or numerical control is the use of control systems such as computers to control industrial machinery and processes, reducing the need for human intervention. In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provided human operators with machinery to assist them with the physical requirements of work, automation greatly reduces the need for human sensory and mental requirements as well. Processes and systems can also be automated. Automation plays an increasingly important role in the global economy and in daily experience. Engineers strive to combine automated devices with mathematical and organizational tools to create complex systems for a rapidly expanding range of applications and human activities.Many roles for humans in industrial processes presently lie beyond the scope of automation. Humanlevel pattern recognition, language recognition, and language production ability are well beyond the capabilities of modem mechanical and computer sys.ms. Tasks requiring subjective assessment or synthesis of complex sensory data, such as scents and sounds, as well as high-level tasks such as strategic planning, currently require human expertise. In many cases, the use of humans is more cost-effective than mechanical approaches even where automation of industrial tasks is possible.
1.2 SIGNIFICANCE OF AUTOMATION
For the purpose of AUTOMATION Specialized hardened computers, referred to as programmable logic controller. (PLC), are frequently used to synchronize the flow of inputs from (physical) sensors. and events with the flow of outputs to actuators and even. This leads to precisely controlled actions that permit a tight control of almost any industrial process. Human-machine interfaces (HMI) or computer human interfaces (CHI), formerly known as man-machine interface, are usually employed to communicate with PLCs and other computers, such as entering and monitoring temperatures or pressures for further automated control or emergency response. Service personnel who monitor and control these interfaces are often referred to as stationary engineers. Automation has had a noble impact in a wide range of highly visible industries beyond manufacturing. Once-ubiquitous telephone operators have been replaced largely by automat. telephone switchboards and answering machines. Medic. processes such as primary screening in electrocardiography or radiography and laboratory analysis of human genes, sera, cells, and tissues are carried out at much greater speed and accuracy by automated systems Automated teller machines have reduced the need for bank visits to obtain cash and carry out transactions. In general, automation has been responsible for the shift in the world economy from agrarian to industrial in the 19th century and from industrial to services in the 20th century. Currently, for manufacturing companies, the purpose of automation has shifted from increasing productivity and reducing costs, to broader issues, such as increasing quality and flexibility in the manufacturing process.The old focus on using automation simply to increase productivity and reduce costs was seen to be short-sighted, because it is also necessary to provide a skilled workforce
who can make repairs and manage the machinery. Moreover, the initial costs of automation were high and often could not be recommend by the time entirely new manufacturing processes replaced the old. (Japan's 'robot junkyards" were once world famous M the manufacturing industry ) Automation is now often applied primarily to increase quality in the manufacturing process, where automation can increase quality substantially For example , automobile and truck piston used to be installed into engines manually. This is rapidly being transitioned to automated machine installation, because the error rate for manual installment was around 1-1.5%, but has been reduced to 0.00001%) with automation Hazardous operations, such as oil refining, the manufacturing of industrial chemicals, and all forms of metal working, were always early contenders for automation. Another major shift in automation is the increased emphasis on flexibility and convertibility in the manufacturing process Manufacturers are increasingly demanding the ability to easily switch from manufacturing Product A to manufacturing Product B without having to completely rebuild the production lines. Flexibility and distributed
Fig 1.1 Block Diagram of Industrial Automation
1.3 APPLICATION OF AUTOMATION
ANN - Artificial neural network DCS - Distributed Control System HMI - Human Machine Interface SCADA - Supervisory Control and Data Acquisition PLC - Programmable Logic Controller Instrumentation Motion control Robotics
4) 5) 6) 7) 8)
CHAPTER 2 SENSOR
Sensors are sophisticated devices that are frequently used to detect and respond to electrical or optical signals. A Sensor converts the physical parameter (for example:- temperature, blood pressure, humidity, speed, etc.) into a signal which can be measured electrically. Let’s explain the example of temperature. The mercury in the glass thermometer expands and contracts the liquid to convert the measured temperature which can be read by a viewer on the calibrated glass tube.
2.2 CRITERIA TO CHOOSE A SENSOR
There are certain features which have to be considered when we choose a sensor. They are as given below: 1. Accuracy 2. Environmental condition - usually has limits for temperature/ humidity 3. Range - Measurement limit of sensor 4. Calibration - Essential for most of the measuring devices as the readings changes with time 5. Resolution - Smallest increment detected by the sensor 6. Cost 7. Repeatability - The reading that vanes is repeatedly measured under the same environment
2.3 CLASSIFICATION OF SENSORS:
The sensors are classified into the following antenna: 1) Property 2) Application 3) Power / energy supply requirement 4) Material and Technology Transduction principle is the fundamental criteria which are followed for an efficient approach. Usually, material and technology criteria are chosen lay the development engineering group.
2.3.1 Classification based on property:1) Temperature - Thermistors, thermocouples, RTD's, IC and many more. 2) Pressure - Fibre optic, vacuum, LVDT, electronic. 3) Flow - differential pressure, positional displacement, thermal mass , etc. 4) Level Sensors - Differential pressure, radar, thermal displacement, etc. 5) Proximity and displacement - LVDT, photoelectric, capacitive, magnetic, ultrasonic. 6) others - moisture humidity sensor,Speed sensor
2.3.2 Classification based on Application
1) Industrial use - Process control, measurement and automation 2) Non-industrial use - Aircraft, Medical products, Automobiles
2.3.3 Classification based on power or energy supply requirement
1) Active Sensor - Sensors Mat require power supply are called as Active Sensors. Example: LiDAR (Light detection and ranging), photoconductive cell. 2) Passive Sensor - Sensors that do not require power supply are called as Passive Sensors. Example: Radiometers, film photography.
2.3.4 In the current and future applications, sensors can be classified into groups as follows:1) Accelerometers - These are based on the Micro Electro Mechanical sensor technology. They are used for patient monitoring which includes pace makers and vehicle dynamic systems. 2) Biosensors - These are based on the electrochemical technology, They are used for food testing, medical care device, water testing, and biological warfare agent detection. 3) Image Sensors - These are based on the CMOS technology. They are used in consumer electronics, biometrics traffic and security surveillance and PC imaging
4) Motion Detectors - These are based on the Infra Red, Ultrasonic, Microwave/ radar . They are used in video games and simulations, light. activation and security detection.
2.4 TEMPERATURE SENSOR
This device collects information about temperature from a source and converts into a form that is understandable by other device or person. The best illustration of a temperature sensor is mercury in glass thermometer. The mercury in the glass expands and contracts depending on the alterations in temperature. The outside temperature is the source element for the temperature measurement. The position of the mercury is observed I, the viewer to measure the temperature. There are two basic types of temperature sensors: Contact Sensors - This type of sensor requires direct physical contact with the object or media that is being sensed. They supervise the temperature of solids, liquids and gases over a wide range of temperatures. Non contact Sensors - This type of sensor does not require any physical contact With the object or media that is being sensed. They supervise nonreflective solids and liquids but are not useful for gases due to natural transparency. These sensors use Plank's Law to measure temperature. This law deals with the heat radiated from the source of heat to measure the temperature.
184.108.40.206 Different types of Temperature Sensors
(i) Thermocouple - They are made of two wires (each of different homogeneous alloy or metal) Mich form a meas.., junction by joining at one end. This measufing junction is open to the elements being measured. The other end of the Wre is terminated to a measuring device where a reference junction is loaned. The current flows through the circuit since the temperature of the two junctions are different. The resulted milli-voltage is measured to determine the temperature at the junction. The diagram of thermocouple is shown below.
Fig 2.1 Thermocouple (ii) Resistance Temperature Detectors (RID) — These are types of thermal resistors that are fabricated to alter the electrical resistance with the alteration in temperature. They are very expensive than any other temperature detection devices. The diagram of Resistance Temperature Detectors is shown below.
Fig 2.2 Resistance Temperature Detectors
(iii) Thermistors — They are another kind of thermal resistor where a large change in resistance is proportional to small change in temperature.
Fig 2.3 thermistor
2.5 PROXIMITY SENSOR
A proximity sensor detects the presence of objects that are nearly placed without any point of contact. Since there is no contact between the sensors and sensed object and lack of mechanical parts, these sensors have long functional life and high reliability. The different types of proximity sensors are Inductive Proximity sensors, Capacitive Proximity sensors, Ultrasonic proximity sensors, photoelectric sensors, Hall-effect sensors, etc.
Working Process :- A proximity sensor emits an electromagnetic or electrostatic field or a beam of electromagnetic radiation (such as infrared), and waits for the return signal or changes in the field. The object which is being sensed is known as the proximity sensor's target.
2.5.1 Inductive Proximity sensors They have an oscillator as input to change the loss resistance by the proximity of an electrically conductive medium. These sensors are preferred for metal targets. 2.5.2 Capacitive Proximity sensors They convert the electrostatic capacitance variation flanked by the detecting electrode and the ground electrode. This occurs by approaching nearby object with a variation in an oscillation frequency. To detect the nearby object, the oscillation frequency is transformed into a direct current voltage which is compared with a predetermined threshold value These sensors are preferred for delectric material and fluids . 2.5.3 Ultrasonic sensor They are used to detect the presence of an object. It achieves this by emitting ultrasonic waves from the device head and then receiving the reflected ultrasonic signal from the concerned object. This helps in detecting the position, presence and movement of objects. Since ultrasonic sensors rely on sound rather than light for detection, it is widely used to measure water-levels, medical scanning procedures and in the automobile industry. Ultrasonic waves can detect transparent objects such as transparent films, glass bottles, plastic bottles, and plate glass, using its Reflective Sensors. 2.5.4 Optical sensor Photoelectric sensor are small and fairly simple optical switches. They are used in place where the environment contains conductive dust and more
sensing range is required. They have two main components : an emitter and a receiver . The emitter contains light source which is either LED or LASER . The receiver contains an Opts electronics element such as photo transistor or a photodiode that detects the light from the emitter and converts the received light intensity is “tuned” to the pulse frequency of its emitter and ignore all of the other ambient light , which is gathered by it's lens. There are three types of photoelectric sensors are available, • Thru beam • Diffused beam • Retro reflective type
i. THRU BEAM – these are consist of two devices , a light emitter and a
light receiver .these two devices are kept apart facing each other. Emitter sends pulse in the range of infrared rays , which is received by a receiver placed opposite to the emitter. On any interruption of these rays by the target , the receiver gives a signal, which is amplified & fed into the output section of the sensors. Applications– • sensing the fill level of liquid before sealing • Counting objects
DIFFUSED MODE –
these are consist of emitter and receiver
together. The emitter emits infrared rays are diffused on the receiver by the surface of object to be sensed, and switches it's output. When there is no target , no light is reflected to the receiver .
Applications – • Position sensing of objects • Counting of objects
iii. Retro reflective mode – these are consist of emitter and receiver in one
device & a reflector.the reflector reflects the rays emitted by the emitter to receiver.the sensing of objects occurs,when these rays are interrupted . Applications – • Edge detection in paper/sheet metal • Effective for non reflective surface
CHAPTER 3 FRONT CONTROL AND SWITCHING CONCEPTS
An electrical switch is any device used to interrupt the flow of electrons in a circuit. Switches are essentially binary devices: they are either completely on (“close”) or completely off (“open”), There are many different types of switches, front panel controls are nothing but different devices installed on a machine/control panel/operation console for the operator such as 1) Push buttons 2) Selector switches 3) Rocker Switches 4) Indication Lamps 5) Rotary/Cam 6) Hooters & Buzzer
3.1 PUSH BUTTON Push button switches are two-posit■to devices actuated with a button that is pressed and released. Most pushbutton switches have an internal sprIng mechanism returning the button to its out, or unpressed," position, for momentary. Pushbutton switches will latch alternately on or off with every push of the button. Other pushbutton switches stay in 'Brhs.d," Poet . nth the button is pulled back out. Ohs last type of pushbutton witches usually have a
mushroom-shaped button for easy push-pull Mon.
Working principle & application : It is a spring return switch. The NO NC contacts which can be connected as accessories get activated when the push button element is passed These Ott useful for giving momentary signal to the actuators. For example, in a motor starter the motor by passing push button momentarily, motor contactor gets latched.'
Ordering Information : • colors: such as Red, green ,Yellow,White,white,blue • illuminated/No illuminated • structure type: Flush mounting • Protection type • mushroom type • mushroom type lockable • diameter:diameter in mm such as 8,16, 22 mm
AC(V/I): 24/4,120/3,230/2 DC(V/I): 24/0.5,110/0.2
2.2 TOGGLE SWITCH
Toggle switches are actuated by a lever angled in one of two or more numbers. The common light switch used in household mono is an example of a toggle munch. Most toggle switches come to rest in hon of their lever positions, while others have an internal Wong mechanism returning the lever to a certain normal problem, allowing for what is called 'momentary" operation
Symbol of Circuit diagram :-
Working principle & application : These are similar in working to that of selector switches, and are generally used. switching of low power appliances, These switches are not modular in
nature i.e. extra contacts can't be added. • Contact types : Single pole double through (SPOT) Double pole double through (DPDT) • Ratings such as 1.5A, 3A, 5A, 10A
Indication lamp :-
Symbol of circuit diagram:-
Working principle & application:
These are used l'or visual indication of process. For example for the indication of whether some machine is ON OFF
• Type :- LED type, Lamp type Lamp • colors:- Red, Green, Yellow, WILD, and Blue
2.4 Selector Switch
Selector switches are actuated with a rotary knob or lever of some sort to select one of two or more positions.
Symbol of circuit diagram:-
Working principle & application: Selector switch are used to select position, mode or actuators. These are useful in control & low power control systems.
Ordering Information • Types: Spring return, Stay put (Maintained contact) • Switching sequence, 2 or 3-way with/without OFF position. • Illuminated/Non illuminated • Key selector two position • Right position
Len position Right & Left position.
Working principle & application: These are similar in working to that of selector switches, but due to their compactness, they are useful for switching of low power appliances. Ordering information : Contact types: ON/OFF Momentary ON Momentary OFF Both sides ON Center OFF with both Odes ON Single pole / Double pole Rating: 2, 4, 6, 10
Rotary / Cam Switches
Working principle & application: Rotary switches are like selector switches except it has three or more positions used to select position, mode or actuators. These are useful in control circuits & low power control systems
Buzzers & Hooters
they are small in size & there audible sound range is limited, whereas hooters & sirens sound can be reachable up to 2 K.M. Buzzer are normally used in low power application. Hooters are used in industry as an alarm or fault generator. Hooter uses different sound These are used where audible sound signal/ alarm is to be generated. Buzzers modes to signal various alarm level.
switching is used to have control over any electrical circuit. Switching is nothing but maiking and breaking of an electrical circuit . NO- Normally open configuration : in it's deactivated condition ie, NO mode,it does not allow the power supply to reach to load and no electrical current flows through load.In this condition , contact& load, both are deactivated . After the activation f contact it allows the power supply to reach to load (it makes the contact) and the load decides the electrical current flowing through it & contact. Activation condition of NO contact is known as Functionally Closed , i.e , FC . In this condition contact and load , both are activated. NC – Normally closed configuration in it's deactivated condition ie, NC mode,it allow the power supply to reach to load and the electrical current flows through load. Though contact is deactivated, load is activated . After the activation of contact it does not allows the power supply to reach to load (it breaks the contact) and hence,nocurrent flows through it . Activation condition of NC contact is known as Functionally Open, i.e , FO . In this condition contact is activated and load is deactivated.
CHAPTER 4 DRIVES
4.1 AC DRIVE
In an induction motors, when the 3-phase stator windings, are IS by 3— phase AC supply then, a magnetic flux of constant magnitude, but rotating at synchronous speed, is set up. The flux passes through the air gap; sweeps past the rotor surf., and so cuts the rotor conductors, which as yet, are stationary. Due to the relative speed between the rotating flux and the stationary conductors, an E.M.F. is induced in the letter according A Faraday's law of Electro—Magnetic induction. The frequency of the induced E.M.F. is the same as the supply frequency. Its magnitude is proportional to the relative velocity between the flux and the conduct°. Ad Fleming's Right HAd Rule Mves It directions.The Synchronous Speed (Ns) of an induction motor is given by, Ns = (120.1)/ P
where “ F ”= frequency “ P ”= no's of Pole. In an induction motor, the motor run at a speed, which is always less than the speed of the stator field. The difference in speeds depends upon the load on the motor. The difference between the synchronous speed Ns & the actual speed N of the rotor is known as Slip. Therefore, Slip (S) = (Ns - N) / Ns Where, N is the rotor speed. Therefore, Actual speed of shaft CY) = Ns • (I- S). The torque equation . AC motor is given as,
4.2 VOLTAGE/FREQUENCY CONCEPT
The V/F concept is mainly used in AC drives. Therefore AC drives are also known as "V/F DRIVES". In drives it is necessary for a motor to deliver rated torque at set speed. In order to change the speed of AC motor stator frequency is to be changed. Since torque delivered by motor is proportional to the product of the stator current and flux, it is essential that motor flux be to be kept constant. This means at any speed, motor can deliver torque (maximum up to rated torque) demanded by load and is roughly proportional to the product of stator current and motor flux. So we have, Torque = la * Where, la = Armature current which varies with load . = Motor flux Wash ',mans constant 4.2.1 VOLTAGE / FREQUENCY CURVE:
The EMF generated is proportional to the raW at which conductors cut the flux. So we have,
EMF = Rate of change of flux
Therefore, in order to maintain constant flux in motor, the ratio of voltage to frequency is always maintained constant so that motor can deliver rated torque through out the speed range.
4.2 DC MOTOR
DC MOTOR BASICS An electrical motor is a machine, which converts electrical energy into mechanical energy. The basic principle is that when a current carrying conductor is placed in a magnetic field it experiences a mechanical force whose direction is given by Fleming's VII hand rule. There is no basic difference between the construction of a dc generator and do motor the same machine can be used as a generator or a motor. In case of a dc motor the field electromagnet kart armature conductors are supplied with the current from mains supply and mechanical force is obtained by rotation of armature. In case of dc motor, the e.m.1 (E) is less than the applied voltage (V) and the direction of the current (Ia) is the reverse of that when the machine is used as a generator. E = V — laRa OR V = E IaRa As the e.m.f. generated in the armature of a motor is in oppose on to the applied voltage, it is also referred as 'Back emf '
4.3.1 WHY WE USE A DC DRIVE ? Basically, DC drive is used due to following things: DC drive has precise control on speed & torque. DC drive is a soft starter means it has ramp input. It is useful in order to minimize the maintenance of the DC motor. DC drive has good efficiency, which is around 80 % to 95 % giving good result during running condition of DC motor. DC drive gives speed regulation means it can sense load (From no-load to full-Imd) in proper manner & maintain the same speed. DC drive has speed controlling range from 0% to 100%, so it can control speed from 0 mm rated rpm of the motor. DC drive has 0.01% accuracy which means motor can run at 001% of rated rpm speed. DC drive gives various types of protection over the motor control like Feedback loss, Integrated Overload, Ph am sequence failure, Under Co hap, Over Voltage, Over Current, Over Speed, Over temperature etc.
4.4 SPEED CONTROL OF DC MOTOR USING DC DRIVES
The speed control of DC motor is given by N = (Va laRa) From the above equation we can say that, the speed of separately excited DC motor can be varied in two ways. I Field current is kept consMnt avhile the armature voltage is varied from zero to rated value. 2 Armature voltage is kept constant at the rated value and field current is varied from maximum to minimum. These hvo speed control result in speed-torque characteristics, which are different from each other. Armature voltage control gives constant torque and variable power characteristics while variable field flux gives constant power and variable torque characteristics
220.127.116.11 Armature Voltage Control: This method is used for controlling speed up to base speed of the motor. Base speed is the ,speed at which the motor deliver. the rated power and torque at rated armature and field current. Since the field flux is kept constant, the torque is entirely dependent on the value of armature current. Once the value of starting, torque i.e. starting current is determined, the armature volt,e .n be varied smoothly ,up to base speed, keeping the armature current within the fixed limit. As the motor speeds,Eb increases and the current tends to lower but since the voltage is also increase the current level can be mainlined. As the current and the flux are kept constant the motor has constant torque characteristics and power machine rises. By abrading the armature voltage below the nominal rated voltage, motor can be made to operate at various speeds in a wader range delivering lull torque and reduce power output. It is not possible to operate the motor at higher than the base speed by increasing the armature voltage above nominal rated voltage. This method a speed control is used in crimes, rolling mills etc. Thus up to base speed the motor can be controlled easily by controlling the armature voltage, called as 'constant torque application' 18.104.22.168 Field current control: Up to the base speed, the motor is controlled by armature voltage control. Now if the speed required is more than the base speed and the armature voltage is not be increased beyond the rated voltage, the choice is to decrease the field flux. To achieve this, the field current is to be decreased. This is called 'constant power application' since power remains constant. This is also termed as field weaking of the system.
Advantage & Disadvantages of DC Drive
CHAPTER 5 TIMERS
In modern, high tech and professionally managed organization true regard of time is a prime necessity, proper, uniform, synchronous timing means no more production losses, less man hour’s wasted and precious resources saved. Timer is an effective tool in each and every industry. They keep beat of an enterprise or an industry in synchrony. Timer is a relay with an additional facility of time. It is a frequently used automation product. It starts counting time as soon as Auxiliary power supply or a start pulse is applied and actuates output according to operational mode configured. Timer coil represents an electronic circuit, it may have digital display and potential free output contacts are essential part of Timer. These potential free contacts are available in standalone NO/NC versions or are available in various combination thereof.
Fig 5.1 Timer
• Control circuitry of various machines & processes like… • Molding machines • Air-conditioning equipment & plants, chillier packages • Pharmaceutical machinery • Cement industries • Mixing industries • Photographic equipment • Textile/Sugar/Steel/Fertilizer processes • Power generation plants
5.1.2 Common examples • Traffic signal control • Hand dryer • Microwave oven • Washing machine • Television sets • Streetlights • Alarm clocks • Camera
5.3 OPERATING MODES OF TIMER
1) on delay 2) interval 3) cyclic OFF first 4) Cyclic ON first 5) star delta timer 6) OFF delay
5.3.1 ON Delay Timer When input auxiliary power or start instruction pulse is applied, time measurement for ‘t’ seconds beings. Time measurement is shown on the digital display, if it is available in the model. During time measurement, the output relay remains in its de-activated condition. At the end of the time measurement output relay contacts get activated. These output relay contacts get de-activated when power is removed or reset pulse is provided thus resetting the timer for the next cycle.
5.3.2 INTERNAL timer When input auxiliary power OR start instruction pulse is applied, time measurement for ‘t’ seconds beings. Time measurement is shown on the digital display, if it is available in the model. During time measurement, the output relay contacts get activated and at the end of the time measurement output relay contacts again get de-activated. One can reset the operation at any moment by providing Reset pulse or switching OFF/ON the auxiliary power supply. 5.3.3 Cyclic OFF FIRST Timer When input auxiliary power OR start instruction pulse is applied, time measurement for ‘t1’ seconds beings, which is known as OFF TIME. Time measurement for ‘t1’ is shown on the digital display, if it is available in the model. During this t1 time measurement, the output relay contacts remain deactivated and after completion of t1 time measurement output contacts get activated and timer starts time measurement for t2 duration which is known as ON TIME. Time measurement t2 is shown on the digital display, if it is available and after completion of t2 time measurement, output relay contacts get deactivated again. Till the auxiliary power supply is on, this OFF/ON cycle repeat continuously. One can reset the operation at any moment by providing Reset pulse or switching off/on the auxiliary power supply
5.3.4 Cyclic ON FIRST Timer When input auxiliary power OR start instruction pulse is applied, time measurement for ‘t1’ seconds beings, which is known as ON TIME. Time measurement for ‘t1’ is shown on the digital display, if it is available in the model. During this t1 time measurement, the output relay contacts remain
activated and after completion of t1 time measurement output contacts get deactivated and timer starts time measurement for t2 duration which is known as OFF TIME. During the Time measurement t2 is shown on the digital display, if it is available and after completion of t2 time measurement, output relay contacts get de-activated again. Till the auxiliary power supply is on, this ON/OFF cycle repeat continuously. One can reset the operation at any moment by providing Reset pulse or switching off/on the auxiliary power supply
5.3.5 OFF Delay Timer upon application of input auxiliary power, the output relay contacts get activated. These outputs contacts remain activated till the auxiliary power supply is in and further remain activated even after the withdrawal of auxiliary power supply for the pre set time “t”.Actually time measurement begins after the withdrawal of auxiliary power supply and output contacts get deactivated only after the preset time “t” is elapsed. These types of Timers are used where the next process require sometime for completion of incomplete job or to come to normal condition after power supply is off.
Fig 5.3 Operation of timer
This report has discussed the role that Automation in Electrical and Electronics have in the efficient design and control of mechanical processes.Also discussed was the understanding Automation and controlling motor and machines involved with it. Finally, the report has discussed relay logic and the evolution that auto control logic made from it. 1. Automation History: This section discussed the history and advancement controls technology, with a comparison of machines logic controllers and hardwired relays. 2. automation components: This section defined what is automation control and logic and described all hardware associated with it. 3. Automation in electrical and electronics: This section covered various technique of automation machines. 4 Automation : This section contain all basic introduction of automation system.
G.B.Gupta, Rajeev gupta, SCADA Security Strategy, Theory & performance of ELECTRICAL MACHINES, August 8, 2001
www.automationnews.com www.princetonindiana.com/wasetewater/Pages www.ref.web.cern.ch/ref/CERN www.sss-mag.com/automation.html www.automation.comwww.scrib.com