Electrical Lab Manual PDF - Delhi Technological University

DELHI TECHNOLOGICAL UNIVERSITY LABORATORY MANUAL SKILL ENHANCEMENT COURSE (Ist Semester) Laboratory: Electrical Workshop (SEC 1) (Part-I) DEPARTMENT OF ELECTRICAL ENGINEERING DELHI TECHNOLOGICAL UNIVERSITY (Formerly Delhi Co...

DELHI TECHNOLOGICAL UNIVERSITY LABORATORY MANUAL SKILL ENHANCEMENT COURSE (Ist Semester) Laboratory: Electrical Workshop (SEC 1) (Part-I) DEPARTMENT OF ELECTRICAL ENGINEERING DELHI TECHNOLOGICAL UNIVERSITY (Formerly Delhi College of Engineering) BAWANA ROAD, DELHI-110042 August 2023 ELECTRICAL ENGINEERING DEPARTMENT  DELHI TECHNOLOGICAL UNIVERSITY ELECTRICAL ENGINEERING DEPARTMENT  DELHI TECHNOLOGICAL UNIVERSITY List of Experiments (Part-I) 1. To prepare a single line circuit diagram for staircase wiring using 2-way switches, bill of materials and build up electrical wiring on wooden Board. Evaluate the total cost with all electrical fixtures. 2. To prepare a single line circuit diagram for bed switch wiring using 1-way switches, bill of materials and build up electrical wiring on wooden Board. Evaluate the total cost with all electrical fixtures. 3. To study the various Low Tension (LT) MCBs, Fuses, Switches, Lamps, LED tube light and bulbs, Regulators, Electrical Fixtures, Variac, and explore the limitation of their usages. 4. To study different types of LT conductors and SWG cables. 5. To measure Lumen of various lamps. ELECTRICAL ENGINEERING DEPARTMENT  DELHI TECHNOLOGICAL UNIVERSITY ELECTRICAL ENGINEERING DEPARTMENT  Electrical Symbols S. No. Name Symbol S. No. Name Symbol 1. Electrical Wire 20. Rheostat (IEC) 2. Connected Wires 21. Trimmer Resistor 3. Not connected 22. Thermistor wires 4. SPST Toggle 23. Photoresistor Switch 5. SPDT Toggle 24. Polarized Switch capacitor 6. Pushbutton Switch 25. Capacitor (NO) 7. Pushbutton Switch 26. Variable (NC) Capacitor 8. DIP Switch 27. Inductor 9. SPST Relay 28. Iron Core Inductor 10. SPDT Relay 29. Variable Inductor 11. Jumper 30. Voltage Source 12. Earth Ground 31. Current Source 13. Chassis Ground 32. AC Voltage Source 14. Common/Digital 33. Generator Ground 15. Resistor (IEEE) 34. Battery Cell 16. Resistor (IEC) 35. Battery 17. Potentiometer 36. Controlled (IEEE) Voltage Source 18. Potentiometer 37. Controlled (IEC) Current Source 19. Rheostat (IEEE) 38. Voltmeter S. No. Name Symbol S. No. Name Symbol 39. Ammeter 55. JFET-P Transistor 40. Ohmeter 56. NMOS Transistor 41. Wattmeter 57. Motor 42. Lamp/Light Bulb 58. Transformer 43. Lamp/Light Bulb 59. Electric Bell 44. Lamp/Light Bulb 60. Fuse 45. Diode 61. Bus 46. Zener Diode 62. Optoisolator 47. Scottky diode 63. Loudspeaker 48. Varicap diode 64. Microphone 49. Tunnel Diode 65. Operational Amplifier 50. Light Emitting 66. Schmitt Diode Trigger 51. Photodiode 67. Analog to Digital Converter 52. NPN Bipolar 68. Digital to Transistor Analog Converter 53. PNP Bipolar 69. Crystal Transistor Oscillator 54. Darlington Pair 70. Direct Current  Electrical Safety Electrical safety is a general practice of handling and maintaining electrically powered equipment to prevent incidents. Adequate training is required to properly identify and control hazards to keep the environment safe for those around. 1. Electrical Hazards Examples 2. Tips for Safety : 2.1. Overhead Power Lines: Overhead powered and energized electrical lines have high voltages which can cause major burns and electrocution to workers. Remember to maintain a minimum distance of 10 feet from overhead power lines and nearby equipment. 2.2. Damaged Tools and Equipment: Exposure to damaged electrical tools and equipment can be very dangerous. Do not fix anything unless you are qualified to do so. 2.3. Inadequate Wiring and Overloaded Circuits: Using wires of inappropriate size for the current can cause overheating and fires to occur. Use the correct wire suitable for the operation and the electrical load to work on. Use the correct extension cord designed for heavy-duty use. 2.4. Exposed Electrical Parts: Examples of exposed electrical parts include temporary lighting, open power distribution units, and detached insulation parts on electrical cords. 2.5. Improper Grounding: The most common electrical violation is the improper grounding of equipment. Proper grounding can eliminate unwanted voltage and reduce the risk of electrocution. 2.6. Damaged Insulation: Defective or inadequate insulation is a hazard. Be aware of damaged insulation and report it immediately. 2.7. Wet Conditions: Never operate electrical equipment in wet locations. Water greatly increases the risk of electrocution especially if the equipment has damaged insulation. 3. Understanding Safety Signs: There are four main categories of signs and they are: 3.1. Green Emergency – square or rectangular with a white image on a green background. Found on emergency exits, escape routes, and on first aid kits. 3.2. Blue Mandatory – round sign with white images on a blue background. Instructions to wash hands, use a safety harness, or wear safety glasses for example. 3.3. Yellow Warning – triangular with black edging and black image on yellow background. Warnings of electric shocks, biological hazards, magnetic fields, and other nearby hazards. 3.4. Red Prohibition – round with black image on white background and red edging with a red diagonal line. Instruction to not touch, not enter, no access, and even evacuation. 4. Electrical Safety Signs: These signs provide information regarding the type of accident that may occur and the possible outcome. 2.1 Lightning Bolt the common signal for electricity is a lightning bolt. A one-word description may be written across the sign to indicate the danger. 2.2 Bolt through this voltage or shock hazard symbol Hand indicates that injury or death may occur via high-voltage electrical equipment 2.3 Bolt with identifying buried electricity cables Downward- pointing Arrow 2.4 Skull and fatal Cross Bones INSTRUCTIONS FOR EXPERIMENTS IN THE ELECTRICAL LAB/WORKSHOP General Instructions The aim of performing experiments are to develop skills and attitudes that will help students to deepen their understanding through relating theory to practice and enable them to operate effectively and professionally in an engineering workplace. Each student has to follow the following laid down procedures: 1.1 Student must bring an auxiliary notebook during each laboratory exercise to record meticulously all the experimental observations during the experiment, linking the theory and practice. 1.2 Read the experiment notes, available in the Lab, prior to carry out the experiment. Follow the correct operating procedure for each instrument. The lab teacher and technician/instructor will provide necessary guidance. 1.3 Take the necessary electrical and mechanical tools/instruments from the lab instructor(s), and use them carefully and efficiently. 1.4 Measure and record all the data in proper format in the auxiliary notebook and get it signed by the concerned teacher(s) after the experiment is over. 1.5 If you loose your laboratory notebook, you will not be able to write the laboratory report and you will have to do the experiment again. 1.6 If any equipment/tool is out of order or malfunctioning, report to the instructor(s). Do not use equipment that malfunctions or in your opinion may endanger yourself or your companion. It is the responsibility of the student to report malfunctioning of any equipment. 1.7 Analyse the experimental observation data and present the results and prepare a complete report on the experiment in a practical file/report. Every student must prepare their own written laboratory report/file. 1.8 The file must contain name of the student, name of the experiment, date of the experiment done and page no. in chronological manner at the indexing page of the file. 1.9 The laboratory report/file should include inter-alia the following sections methodically: (i) Aim, Apparatus/Instruments, Software Programs, Introduction/Theory, Experimental set up, Circuit Diagrams, Procedure, Data analysis, graph, results/ error analysis, and discussion linking the theory and practice. (ii) All equations, tables and figures must be numbered in sequence. Tables, graph and figures must include a caption that describes their content. All figures must be clearly specified. (iii) In the graph, the data points must be clearly marked and coordinate axes must be given meaningful names and proper units. (For any instruments used, provide either the make and model or a schematic drawing of the setup). (iv) The practical file and the auxiliary notebook are to be submitted to the concerned teacher for mid-term and end semester evaluation to determine the overall grade. (v) Note that computers and instruments and any tools to be used to carry out an experiment should neither be used unfairly nor for any personal work.  ELECTRICAL SAFETY INSTRUCTIONS IN LAB/WORKSHOP Injuries to the human being caused by electricity include electrical shock, burns, and falls. Electrical shock occurs when current passes through the body. Electrocution is a fatal electrical shock. Low voltage or low current does not mean low hazard. Even, less than 10 mA can cause a painful shock and loss of muscular control, and 50 mA can be very fatal. In order to avoid any such hazards/injuries, the following safety precautions should be followed: Use tools designed for electrical work that have a non-conductive cover. Use electrical cords only if they are in good condition. Cords must not be cracked, frayed, or have corroded prongs. Choose an extension cord appropriate for the current that will be flowing through it to avoid overheating and should be inspected before each use. Too much current flowing through a wire can cause a power cord to overheat and start a fire. Sparks from electrical equipment can ignite flammable materials. Do not leave cables and cords unsecured and hanging in areas where they can pose a trip and movement hazard. Do not leave electrical circuits exposed. Do not block access to electrical panels. Whenever possible, completely de-energize (e.g. capacitors charge) the system before performing any work. Use appropriate amp rating (e.g., 10 amps, 15 amps), voltage and type of circuit breakers and fuses ( safety devices) that protect equipment from high currents or voltages and prevent overheating of electrical wires. Always disconnect the circuit or unplug equipment before inserting an in-line fuse. Never insert in-line fuses into a live circuit. If the new fuse blows, find the reason, or have the equipment checked. Avoid being grounded. Stay at least 6 inches away from all metal materials, walls, and water sources. Wear shoes with thick, insulating soles or use non-conductive mats. Use voltmeters with appropriate rating for the voltage to be tested. A standard voltmeter could explode when subjected to a high voltage. Learn the location of your electrical panels and shut-off switches so you can quickly disconnect power in the event of an emergency. Do not allow cords to dangle from counters or hoods in such a manner that equipment could be unplugged, fall or cords could be tripped over. Do not allow cords to contact hot surfaces to prevent melting insulation. Do not lift a piece of electrical equipment by the cord or pull the cord to disconnect from the outlet in order to prevent damage. Portable power supplies are commonly used in the lab. These devices are extremely high electrical energy sources and must be used carefully. Never attach an exposed connector such as an alligator clip to a power supply.  Avoid contact with energized electrical circuits. Only qualified electrical workers may install, service or repair electrical equipment. Never wear rings, watches, bracelets, necklaces, or other electrically conductive jewellery. No unauthorized experiments should be performed. In case of an accident, the laboratory teacher/ instructor(s) should be immediately informed. Silence to be maintained in the laboratory.  INSTRUCTION SHEET FOR EXPERIMENT No. 1 AIM: To prepare a single line circuit drawing for stair case wiring using 2-way switches, bill of the material and build up wiring on wooden board. Evaluate the total estimated cost with all electrical fixtures. APPARATUS: Screw driver (12”), plier (8”), Wire cutter & stripper, electrician knife (6”), hand saw (12”) and line tester. MATERIAL REQUIRED: S.No. Material Specification 1 PVC insulated copper wire 3/20 SWG 2 2-way switch 240V, 6A 3 Bulb holder Batten type 4 Round block PVC 5 Casing-capping PVC 0.75” 6 Wooden screw 2” 7 Wooden screw ½” 8 Gang box 1-way PVC 9 Bulb 100W, 240V 10 Insulation tape PVC Route Diagram Wiring Diagram PROCEDURE: 1. Make the route diagram on the wooden board by deciding the proper placement of bulb and switches. 2. Cut the casing-capping of required length. 3. Fix the casting on the route defined with the help of wooden screws. 4. Lay the wires of proper length in casing. 5. Fix the switches on the gang boxes and bulb holder on the round block. 6. Make connections of the bulb and the switches. Fix the switches and bulb holder on their place with the help of wooden screws. 7. Get your connections checked by the teacher and then switch ON the supply and test the wiring. 8. Make the truth table according to the relationship of input and output. ESTIMATING TOTAL COST: S.No Material Specification Qty. Rate Cost and type 1 PVC insulated 3/20 SWG copper wire 2 2-way switch 240V, 6A 3 Bulb holder Batten type 4 Round block PVC 5 Casing-capping PVC 0.75” 6 Wooden screw 2” 7 Wooden screw ½” 8 Gang box 1-way PVC 9 Bulb 100W, 240V 10 Insulation tape PVC Labour Cost Total  INSTRUCTION SHEET FOR EXPERIMENT No. 2 AIM: To prepare a single line circuit drawing for bed switch wiring using 1-way switches, bill of the material and build up wiring on wooden board. Evaluate the total estimated cost with all electrical fixtures APPARATUS: Screw driver (12”), plier (8”), Wire cutter & stripper, electrician’sknife (6”), hand saw (12”) and line tester. MATERIAL REQUIRED: S.No. Material Specification 1 PVC insulated copper wire 3/20 SWG 2 1-way switch 240V, 6A 3 Bulb holder Batten type 4 Round block PVC 5 Casing-capping PVC 0.75” 6 Wooden screw 2” 7 Wooden screw ½” 8 Gang box 1-way PVC 9 Bulb 100W, 240V 10 Insulation tape PVC Route Diagram Wiring Diagram PROCEDURE: 1. Make the route diagram on the wooden board by deciding the proper placement of bulb and switches. 2. Cut the casing-capping of required length. 3. Fix the casting on the route defined with the help of wooden screws. 4. Lay the wires of proper length in casing. 5. Fix the switches on the gang boxes and bulb holder on the round block. 6. Make connections of the bulb and the switches. Fix the switches and bulb holder on their place with the help of wooden screws. 7. Get your connections checked by the teacher and then switch ON the supply and test the wiring. 8. Make the truth table according to the relationship of input and output. ESTIMATING TOTAL COST: S.No Material Specification Qty. Rate Cost and type 1 PVC insulated 3/20 SWG copper wire 2 1-way switch 240V, 6A 3 Bulb holder Batten type 4 Round block PVC 5 Casing-capping PVC 0.75” 6 Wooden screw 2” 7 Wooden screw ½” 8 Gang box 1-way PVC 9 Bulb 100W, 240V 10 Insulation tape PVC Labour Cost Total  EXPERIMENT NO. 3 AIM: To study the various low tension (LT) MCBs, fuses, switches, lamps (LED) tube light and bulbs, fluorescent tubes, incandescent bulbs, regulators, electrical fixtures, variac, earthing and explore the limitation of their usages. Background: A basic electrical circuit inter-alia consists of load, power supply source and protection devices. Lighting is the most common type of load, which can be done through bulbs such as incandescent, fluorescent, LED , etc. Fuses and MCBs are used to safeguard any equipment from damages caused due to short circuits or overcurrent. Other desirable components which are used to increase controllability and aesthetics of system are switches, fan regulators, electrical fixtures, and so on. The power lines that transport energy from the local distribution substation to the homes or other buildings of users are referred to as LT (Low Tension) lines, and they operate between 230V to 440V. LT lines may use conductors that are neither fully nor partially insulated due to the lower voltage levels involved. Basic electrical components used widely in electrical circuit are narrated below: 1. Low Tension MCB (Miniature Circuit Breaker) : It is an electromechanical device that works based on the electromagnetic as well as the thermal properties of the electric current. It offers improved operational safety. 1.1. To understand the working Principle of MCB: An electromagnetic mechanism present inside the MCB helps it to instantaneously interrupt the current flow during short circuits and the bimetallic strip present in it helps it to interrupt the current flow during overloads. When the current overflow occurs, the bimetallic strip gets heated and deflects by bending. The deflection of the bi-metallic strip releases a latch. The latch causes the MCB to turn off by stopping the current flow in the circuit. 1.2. Applications of MCBs: Home, Electrical Panels, Heaters, Lights, Industries, etc. (industries with up to 30 kA of power supply) 1.3. Types of MCB: 1.4. Types of MCB based on the number of poles: Single-pole MCB Double pole MCB 3-pole MCB 3- poles and a neutral, 4-pole MCB A single-pole The double pole A three-pole circuit Three poles and a neutral MCB circuit breaker has circuit breaker has breaker has three protects the three phases of the one switch and also two switches and switches, and they circuit. It also has a neutral switch. protects a single also protects two- also protect the three A four-pole MCB contains four phase of the circuit. phase and neutral. phases. switches for three phases, and a neutral. But unlike the former, the latter protects all the phases and the neutral. They are used in places with an unbalanced circuit. 1.5. Types of MCB based on Amps Ratings: Some of the most frequently encountered load capacities for commercial MCBs are 6 amps, 10 amps, 16 amps, 20 amps, 25 amps, and 32 amps. Selection 1.6. Selection of suitable of suitable circuit MCB for house breaker wiring: for house wiring (MCB & RCD) Room one (load 1) total load is 7.5 ampere, there for we chose 10 ampere circuit breaker Room one (load 2) total load is 15.6 ampere there for we chose 20 ampere circuit breaker Room two is same load like room one therefore we chose same MCB breakers for this room Kitchen (load 1) total load is 7.5 ampere there for we select 10 ampere CB. Water heater total load is 10.90 ampere therefor we select 16 ampere Circuit breaker. 2. Electrical Fuses: An electrical fuse is a safety device to provide protection of electrical equipment against the excessive current in an electrical circuit and to prevent  short circuits. Figures as shown below are the different kind of fuses being used for various equipment: 2.1. To understand the working Principle of a Fuse: When a high current flows through an electrical circuit with a fuse connected , the fuse wire gets heated (i2Rt) or melts due to short circuiting or overloading. Hence the circuit is broken and the current stops flowing. This saves all the appliances of the circuit. For further understanding, take a thin fuse wire made of tin or tin-alloy having low melting point. Place this fuse wire on the porcelain fuse grip and insert the grip into the fuse holder. Now switch on all the electrical appliances of high-power rating like electric iron, water heater, air conditioner, etc. Since the melting point of the fuse wire is much lower, it melts and breaks the circuit. The phenomenon of fuse melting on over current can be practically experienced in a circuit. 2.2. Applications: A fuse of 5 amps is used in circuits where lights and fans are connected whereas a fuse of 15 amps is used in power circuits where appliances like electric  heater, geyser, electric iron and air conditioner are connected. A fuse wire with 5A capacity is thinner than a fuse with 15A capacity. 3. Switches: A switch is a component of an electric circuit that makes or breaks the circuit, turning the components on and off. 3.1. Terminologies related to switches: Pole - number of switch contact sets, Throw - number of conducting positions (used for single and double pole) Way - number of conducting positions. Momentary - switch returns to its normal position when released. Open - off position, contacts not conducting. Closed - on position, contacts conducting, there may be several on positions. 3.2. Types of Switches: 4. Electric Lamps: For illumination, various types of bulbs are in use. For example,, LED light ( also known as solid state lamps), fluorescent tubes, incandescent bulbs, etc. Incandescent bulbs: The invention of Incandescent bulb is an important moment in the history of human existence. An incandescent Light Bulb is a very old technology and very cheap. Its rating may be from 5W to 1000W. 4.1. Components of Incandescent bulb is shown below. It contains a glass globe filled with a noble gas to prevent oxidation. At the center of the globe, there is a metal filament wire, through which electricity passes. The filament heats up as electric current passes through it and as a result, it emits electromagnetic radiation in the form of visible light. The filament used in incandescent bulbs is made of Tungsten element due to its very high melting point. 4.2. Key points about Incandescent bulbs: Once widely used in residential as well as commercial lighting. Gradually being phased out due to their poor energy efficiency. Cheapest of all the light bulbs. Very good CRI (Color Rendering Index), almost equal to 100. More than 95% of energy is dissipated as heat. Low manufacturing cost. Doesn’t need any special circuit or electronics. Directly connect to power supply (AC or DC) and they start to work. 4.3 Fluorescent Lamps: The fluorescent lamps (both long tubes as well as compact lamps – CFLs) are a type of Gas Discharge Lamps, which produce light when electricity is passed through an ionized gas. Most lamps use noble gases such as Argon or Neon along with other materials such as Mercury, Sodium and Metal Halides. The electrons in the ionized gas gets excited when electric current is passed. The change in the characteristic energy of the electrons results in emission of photons (in Ultraviolet, Visible as well as Infrared Radiations). These radiations are converted to visible light by coating the inside of the tube with fluorescent element. Both long tube style and compact fluorescent lamps (CFL) are considered to be low-pressure Gas Discharge Lamps as the maximum pressure in these lamps is around 0.3% of atmospheric pressure. Fluorescent Tubes and CFLs are the alternative to incandescent bulbs due to their low energy consumption and longer life. 4.3.1 Working Principle of CFL: The CFL contains a few key components in the emission of visible light including the presence of elemental mercury vapor, a noble gas (argon, xenon, neon or krypton) and an inner coating called a phosphor which is responsible for producing visible light out of the CFL. 4.3.2 Key points about CFLs: o Used in large commercial buildings, offices, shops as well as homes. o The luminous efficiency is better than that of incandescent bulbs. o Very low CRI values. o Mercury based lamps are not being manufactured due to toxic substances. o Needs an electronic circuit (called Ballast) for proper power supply. 4.3.3 Fluorescent tube light: To construct a fluorescent tube light a lime glass tube, drop of mercury, argon gas, phosphor coating and the electrodes with their mount assemblies are required. Total set up of a lamp requires two bases and choke coil with a starter. The electrode mount assembly is almost similar to the stem press unit in the incandescent lamps. The filaments play both roles as anode and cathode. 4.4 LED bulbs: LEDs are semiconductor devices, essentially a PN Junction Diode that emits light when it is forward biased, work on the electro-luminescence phenomenon. Despite the benefits of extreme low power consumption and reasonably long life, LED Light Bulbs are costly. As the years passed by, the cost of LED Light Bulbs has come down gradually and increasingly being used for lighting in offices, commercial complex, street lights, Automotive industries,  Hospitals, Railways, Stadium, etc. The main advantage of LEDs is its high Luminous Efficacy or high Lumens per Watt ratio. 4.5 Comparative Analysis of Bulbs: 5. Fan Speed Regulators: It regulates or controls the speed of the fan motor. 5.1. Types of Regulators: 5.1.1. Resistive regulator: This is the most common type in household ceiling fans. It works by providing different taps on a wire wound resistor connected in series with the fan. It is economic but considerable power loss as heat at lower speeds, making it inefficient. Also, it is bulky, and lacks aesthetic appeal. 5.1.2. Phase angle-controlled/ Electronic regulator: Phase angle-controlled regulators employ active devices such as DIAC and TRIAC. The basic principle is to change the firing angle of the TRIAC in order to change the voltage across the fan. Continuous speed control and low power consumption are its advantages as compared to resistive type regulators. However, disadvantages are speed control not linear, and expensive. It produces humming sound and causes EMI/RFI interference creating disturbances in TV and radio sets. 5.1.3. Inductive regulator: An inductive type fan regulator has a tapping on the winding of the transformer and the inductive reactance is varied to achieve variation in speed. Speed decreases with the increase in the number of turns of the inductance coil winding. It has low heat power dissipation. But introduction of inductor makes it low power factor, costly, and bulky. 5.1.4. Capacitive regulator (latest): The main purpose here is to control the voltage across the fan. As we know, the voltage across the capacitor is given by the formula V= Q/C where Q is the charge across the capacitor and C is the capacitance. As C increases V decreases. Thus, the voltage across the fan increases, the speed increases. Thus, by employing suitable combinations of capacitors, fan’s speed can be regulated. Rs is a series resistance which is used in series with the capacitor in order to limit the current flowing to the capacitor to a safe value. Rp is a parallel resistance which serves as a discharging path for the capacitor for each supply cycle. Its advantages are that it is energy efficient, no humming sound, linear speed, and high reliability as compared to electronic type regulator. 6. Electrical fixtures/Luminaire: 6.1.1. Luminaires are devices that distribute, filter and transform light emitted by one or several lamps and contain all the necessary accessories to mount, protect and connect them to the power supply circuit, thereby fulfilling a triple function: photometric, mechanical and electrical. Photometrically speaking, these devices are responsible for controlling and distributing the light emitted by the lamp, thereby providing more effective illumination. 6.1.2. Fixtures are things that are secured (or ‘fixed’) to the building. Portable light fixtures are often called lamps, as in table lamp or desk lamp. The various types of lighting fixtures/luminaires is shown below: 7. Variac: A variac or variable autotransformer is a single-coil transformer in which two portions of the same coil are used as the primary and the secondary. Variacs are used to provide variable AC voltage from fixed AC voltage. The voltage can be smoothly varied between turns as the brush has a relatively high resistance (compared with a metal contact) and the actual output voltage is a function of the relative area of brush in contact with adjacent windings. They are available in single phase as well as three phase. 7.1 Advantages and disadvantages: Typically lighter and less costly than a two-winding transformer, up to a voltage ratio of about 3:1; Beyond that range, a two-winding transformer is usually more economical. However, variable autotransformers do not provide the electrical insulation between their windings like regular transformers do. This presents a safety hazard as it possibly allows a high primary’s full input voltage to pass directly to a low secondary’s output. 8. Earthing: Earthing is used to protect you from an electric shock. It does this by providing a path (a protective conductor) for a fault current to flow to earth. It also causes the protective device (either a circuit-breaker or fuse) to switch off the electric current to the circuit that has the fault. An earthing system or grounding system connects specific parts of an electric power system with the ground, typically the Earth's conductive surface, for safety and functional purposes. 8.1. Earthing Rules: According to IEE regulations and IE rules, earth pin in 3 pins plus sockets and 4 pin power sockets must be efficiently and permanently earthed. All metal casings and metal coverings containing or covering electrical supply cable or equipment must be earthed. The metallic frames of generators, transformers, stationary motors etc. Stay wires for the overhead electric lines must be connected to earth at least one strand to the earth wires. 8.2. Fault current without earthing: 8.3. Types of earthing: Earthing, or electrical grounding, is done in housing, wiring, and electrical devices. The various electric earthing systems are as shown. OBSERVATION: S. No. Name of device Rating  EXPERIMENT NO. 4 AIM: To Study different types of LT conductors and SWG Cables APPARATUS/TOOLS REQUIRED: S. No Name of Apparatus/Equipment Specification Quantity 1. Screw Gauge 2. Scale 3. Insulation/Electrical tape 4. Wire stripper/cutter/Crimping tool 5. Screwdriver 7. Tester 8. Wires 9. Alligator Clip 1. Background: The purpose of the low tension (LT) conductors/lines is to transmit electrical energy from the distribution transformer to consumers at a low voltage of 440 volts between phases and 230 volts between phase and neutral. These lines are commonly used to power homes, laboratory small business centers, etc and the conductors being used are neither fully nor partially insulated due to the lower voltage levels involved. In the LT line 4-wires are commonly used: three conductors for three-phase (RYB), and one conductor for Neutral. For single phase line, 2-conductors are used. However, the conductors used to transmit electricity from Sub-stations to Distribution Transformer are known as HT Lines at a voltage ranging from 11 kV to 400 kV or more. HT Lines are erected only at main roads of Cities or villages. 1.1 A basic electrical circuit transmitting power is broadly comprising of five components as shown below: (i) A source of electrical energy (AC or DC) as shown in the fig. (ii) A source of circuit protection (overcurrent), may be Fuse or MCB (iii) Circuit conductors or electric cables (LT lines) to supply power to the loads (iv) Circuit control through electrical switches (ON/OFF, Dimmer, Thermostat, etc.) (v) Circuit load (electric appliances, lamps, electric motors, computers, etc.) which need electricity to work. 1.2 A three-phase 4-wire LT lines from 11kV/400V AC sub-station supplying power to the loads at 400 kV and 230 kV is shown below: 1.3 In LT lines, two different ACSR (Aluminium conductor steel reinforced) conductors are used, one for phase and another for neutral. The conductor which is used for phase is Weasel 6/1/2.59 mm (6 Aluminium strands, 1 steel strands and the diameter of each strand is 2.59 mm) and the conductor used for neutral is squirrel 6/1/2.11( 6 Aluminium strands are there, 1 steel strand and diameter of each strand is 2.11 mm). 2. Wires: Solid or stranded conductors make up a wire. 2.1 Conductors: The most effective electrical conductors are Silver Gold Copper and Aluminium. They are the basic building units of wires and cables. 2.2 Flexible wires: These wires consist of number of very thin strands instead of a single solid conductor as shown above. The conductor is insulated with PVC material and is useful for household portable appliances where flexibility of wire is very important. The typical specifications are 55/0.01mm (55 Cu/Al strands of 0.01mm Dia), maximum current 6A. 2.3 Standard Wire Gauge (SWG) Wire: SWG is a British wire gauge standard which is based on a series of specific wire diameters, with increasing gauge numbers indicating smaller wire sizes. The higher the gauge number, the thinner the wire or smaller the gauge number the wider is the wire. SWG is commonly having non-ferrous Copper and  Aluminium wires. Using correct wire gauge for a specific application is crucial for electrical safety and proper functioning of electrical systems. 2.4 Colour Codes for Wires and Colour Codes for a Resistor: Wiring for AC and DC power distribution branch circuits are colour coded for identification of individual wires. 2.5 Earthing Wire: In every circuit, one wire is connected to the earth, the main function of the earth wire is to protect the sudden damage of the electrical appliances or the electrical instruments due to the sudden voltage increase or the leakage of the current. Earth wire is also used for the safety measures. Accidently if any current is leaked, earth wire as given below of green color helps to ground the leakage of current. 2.6 How to make wire connections and insulated Joints? Most wires are coated in a plastic insulator. Removing insulation off the wire is called "stripping the wire", using a crimping tool. A pair of stripped wires is twisted together side by side with thumb and forefinger. Wrap the electrical tape around the wires tightly 5-6 times, making sure to cover up all the wire. This method would be useful for permanent connections that need insulated joints. Look on your spool of wire and find out what gauge your wire is. Next, cut off a small piece of wire from the spool (start with 4", this wire will just be for practice). Insert 3/4" of the wire into the hole in the wire strippers with the appropriate gauge. Grip the other end of the wire with pliers or very strong fingers and pull the wire strippers towards the closest end of the wire. After a little pressure the plastic insulation should slide off, revealing the stranded wire underneath. With alligator clips, the wires can be connected also. 2.6.1 Electrical Tape: Electrical tape is an economical general purpose insulating tape that has excellent resistance to moisture, abrasion and corrosion. It is used to insulate electrical wires, insulate other material that conduct electricity and make minor repairs to damaged wires. Electrical tape is commonly made from vinyl due to the elongation properties. trouble free installation-Always pay attention to the min and max temperature ratings of the electrical tape to ensure correct using of it. To make sure also that the tape is certified. If the tape is exposed to a flame or heat source, the adhesive on the tape can start to burn, which can cause the tape to catch fire. 2.6.2 How to wrap the electrical tape? The tape is to half-lap, as shown in the picture, which results in a double layer of tape. The rule of thumb is to do a minimum of two half-lapped layers or one and a half times the thickness of the insulation of the wire that you are wrapping, whichever is greater. The tape should be thicker than the insulation, for added protection. The tape is stretched as its being applied, it will provide more insulation protection than when it is applied loosely. To create an effective insulation, you should wrap the tape between 75% of its width to right before the breaking point. Doing this will ensure the tape will be able to withstand the element. 3. Cables: A power cable is an assembly of two or more electrical conductors, usually held together with an overall sheath. Power cables may be installed as permanent wiring within buildings, buried in the ground, run O/H, or exposed. Flexible cables are used for portable devices, mobile tools and machinery. Cables are named according to the formation, voltage and material used. They are also named according to their use, that is, low tension (LT) or high tension (HT) cables, etc., as per voltage and single core, two cores, three cores, 3 &1/2 core, etc. 3.1 Types of cables The types of cables are classified in different ways on the basis of their uses, voltage and type of insulation used for their construction. 3.1.1 Classification based on insulation material: 1. PVC (Polyvinyl Carbide Cable) 2. PILCA (Paper Insulated Lead Covered Armored Cable) 3. XLPE (Cross-linked Poly Ethylene Cable) Generally, PILC and XLPE cables are used in HT (High Tension) network, and oil or gas filled cables are used for EHV (Extra High Voltage) network. PVC armoured cables are widely used for LT distribution where conductor materials are made of Copper or Aluminium.  Low tension cables (LT): The cables which are having a voltage level of below 1.1kV called LT cables. Such cables are used in the application below 1.1kv such as domestic and industrial applications. Mostly PVC or XLPE insulation are used. 3.1.2 The voltage level of the cable depends on the insulation level only. Based on insulation, cables are classified as i. Vulcanized Indian rubber (VIR) cables: A small VIR coating of the tinned conductor is called VIR cables. They are used for house wiring. The main disadvantage of VIR is high Sulphur content corrode the copper. They are not suitable for industrial applications. ii. PVC insulated cables: Poly Vinyl Chloride material is used as insulation. They are suitable for both domestic and industrial applications. The cable withstands up to 75ᵒC. But they are not suitable for high voltage and high-power applications. iii. XLPE cables: A cross-linked polyethylene is called as XLPE cables. They withstand up to 90ᵒC and having a dielectric strength of 20kV/mm. These cables have been found very suitable for all voltages up to 33 kV. iv. Lead sheathed cables: The lead layer is used as insulating material. It is suitable for instrumentation cables. v. Paper insulated cables: Impregnated paper is used as insulation material and having good temperature proper as well as dielectric strength of 30kV/mm. vi. Oil-filled cables: It used in high voltage applications. Oil is used as an insulation medium. vii. External Pressure cables: High-pressure gas+ insulating oil is used as insulation material.  3.1.3 Cables can be classified based on the number of conductors is used in it. They are, i. Single Core: Only one conductor is used for internal house wiring, starter wiring, panel wiring, etc. Example: 1C*2.5sqmm cable. ii. Two core: Two conductors are used for transferring electricity. They are mainly used to transferring single-phase supply, DC supply, two-phase supply, etc. Example: 2C*4sqmm cable iii. Three core: Three conductors are used to transfer 3-phase supply- 3C*6 Sqmm cable iv. Three and a half core: Three core and one is half of the core is called three and a half core, used for transferring 3-phase+Neutral supply. Example: 3.5C*10sqmm v. Four core: 4 cores are used in a single cable. Example: 4C*120sqmm 3.1.4 Flat cable/Flexible cable/Armored cable i. Flat cable: All the core in the cable will be placed in the parallel line. They can be laid on the open ground. ii. Flexible cable: The flexible does not come with the protection armored layer. iii. Armored cable: The metal armored is used as the protection layer which protects the cable from physical damage.. 3.1.5. Current-carrying capacity of the cable with respect to its size in sqmm along with the different core. > Copper cable Current (A) Carrying Capacity (XLPE insulated) Three/Four Cable Size (Sq. mm) Single Core Two Core Core 1 17 13.5 9 1.5 22 17.5 15.5 2.5 30 24 21 4 40 32 28 6 51 41 36 10 69 57 50 16 91 76 68 25 119 101 89 35 146 125 110 50 175 151 134 70 221 192 171 95 265 231 201 120 305 269 239 150 334 300 261 185 384 341 296 240 459 400 346 300 532 458 394 Aluminium cable Current Carrying Capacity (XLPE insulated) Three/Four Cable Size in (Sq. mm) Single Core Two Core Core 4 16 13 11 6 20 16 14 10 25 22 19 16 35 31 28 25 43 41 36 35 65 59 52  50 80 71 63 70 91 80 71 95 120 115 100 120 153 133 118 150 188 161 140 185 230 203 176 240 270 254 220 300 340 314 270 Note that In PVC insulation the same capacity will be reduced by 5% 4 Specification of Conductors and its Cost: 5 Specification of SWG Cables and its Cost:  EXPERIMENT NO. 5 AIM: To Measure Lumen ( Brightness) of various lamps 1. APPARATUS REQUIRED: S.No Name of Apparatus/Equipment Specification Quantity 1. Photometric Integration sphere 1m diameter 1 2. Photometric testing panel 1 3. Lamp holder in the centre of the sphere 42 cm vertically long 1 4. Lux meter 0 – 200000 lux 1 5. Variac/Autotransformer 1ɸ, 2A, 0-270V, VA 1 7. Photo sensor &Temperature Sensor in One each the sphere 8. Lamps Incandescent lamp- 60W, One each CFL- 5W, LED-8W ,2ft Fluorescent tube, etc. 1. THEORY: 1.1 Definitions Radiometry Radiometry is the study of entire optical radiation from light sources i.e. electromagnetic waves in the Ultra Violet (UV), visible and infra-r ed spectrum. It is concerned with the total energy content of the radiation. The most common unit of measurement in radiometry is the watt (W), which is the radiant flux (power). How much radiation energy is released from the light source( watt/m2/steradian) is known as radiance which is measured in watt-sec. Luminous Flux (F) in lumen Luminous flux is defined as “the rate of passage of radiant energy evaluated from a light source according to the luminous sensation produced by it to the human eyes”. The portion of the radiant power capable of affecting the sense of sight is Luminous flux. The unit for  luminous flux is the lumen. It can be measured using a Lumen meter/ Flux meter/photometric sphere. Photometry It is a branch of radiometry and concerned with human’s visual response to light. Photometry examines only the radiation that humans can see. The most common unit of measurement in photometry is the lumen (lm), which measure luminous flux. For monochromatic light of 555nm wavelength, 1 watt = 680 lumens. Light that is visible to the human eyes is a part of electromagnetic spectrum ranging from 400nm (violet) to 700nm (red). Human eyes are most sensitive to radiations of wavelength 5550 A° (555nm) which corresponds to yellowish green color. Luminous Efficacy Luminous efficacy is a measure of how much of the electrical power supplied to the lamp is turned into luminous flux. It’s unit is lumens/watt. Fig.1 Luminous Efficacy of a light source Luminous efficiency Luminous efficiency is a measure of how much of the radiant energy is visible to the human eye. It is unitless and expressed in ‘percentage’. 2.2 PHOTOMETRIC INTEGRATING SPHERE: The photometric Integrating sphere is a hollow sphere made up of a special type of fiber, coated from inside with a reflective coating of Barium Sulphate (BaSO4) powder mixed with paint and water. The inside reflective walls provide reflection to light beams radiated by lamps and integrates them. The radiance of light considers the multiple surface reflections from the sphere-wall, and surface area of the sphere. The light received by the sphere by initial reflection is mostly diffused. The sphere is made up of a special type of fiber which does not cause any variation in temperature of the outer surface with the inside temperature. The vertically long lamp holder placed inside the sphere for holding the lamp is coated with the same coating material as that of the integrating sphere wall. There is a rectangular opening of 13.5”x11.5” size on the one side of the sphere to check and measure the illumination of intensive lightings. 2.2.1 Photo Sensors A photo sensor, well shielded, is placed on one side of the Photometric Integrating sphere(Figs.2a-2c) and is used as a transducer, which converts the light, after multiple reflections of light from the inside coated surface of the photometric sphere, into the electrical signals output. The signal indicates the radiant light energy which ranges from infrared to visible to ultraviolet. It is connected at the back of the sphere at an exit port to sense the integrated light and fitted in such a manner that the light from the source should not fall on it directly. It receives only the integrated light after reflection. The optical fiber cable coming out of the lamp holder output is connected to Photometric Testing Panel. A thermal sensor is used to sense the temperature rise or fall inside the sphere. Fig.2a Photometric integrating Fig.2b FT in the Photometric Fig.2c Bulb in the Photometric sphere integrating sphere integrating sphere 2.2.2 Expression of the radiance, L (radiometric considerations): For an integrating sphere, the resulting radiance (L) of a diffuse surface for an input flux (F)must consider both multiple surface reflections and losses through the port openings  needed to admit the input flux. The total flux incident on the sphere surface is higher than the input flux due to multiple reflections inside the cavity. The radiance, the flux density per unit solid angle is given by the following expression, F  L=  W / m 2 / Sr   As 1 −  (1 − f r ) where, ρ is the reflectance, As is the surface area of the entire sphere illuminated and fr is the port fraction. 2.2.3 Performance Characteristics of incandescent bulb and FT: The variation in power consumption, lumens output, luminous efficacy/efficiency and life of incandescent bulb with the variation of input ac voltage is shown in Fig.3 and Fig.4 respectively. Fig.3 Performance curve of incandescent bulb Fig.4 Performance curve of Fluorescent tube 2.3.4 Photometric testing panel Photometric testing panel (Fig.5) having 5 different digital LCD displays for measurements of luminous flux (lumen), voltage(V), current(A), power, frequency(Hz), power factor, VA and power consumption (W).There is a knob beneath the lumen meter which either read zero or C (calibration) and R (reading). The observations should be taken when the knob is at C&R. The input to the panel is given through a Variac. The optical cable and the wire from the sensor are connected to the cable at the output and the sensor respectively on the back of the panel. There are two fuses, for the input and output, which are rated between 2A to 5A. The panel will give readings accurately when the sphere is closed, otherwise it will give erroneous reading of the lamp. Fig.5 Calibration of Lumen meter in the Photometric panel 2.3.5 Photometric measurements The photometric measurements are made to determine the total luminous flux (lumens), luminous efficacy (lm/W), and luminous intensity (candelas) in one or more directions at various input AC voltages and temperature. The total flux data is to be obtained from the photometric testing panel. The electrical connection between the AC power supply, AC powered bulb/FT under test, and digital photometric testing panel (V,A,f,W,pf,Hz) enables to measure the electrical parameters viz. input RMS AC voltage, input RMS AC current, input power(wattage) of the AC powered bulbs/FT, input frequency, and power factor. When the specific lamp is switched ON, the panel will give the reading of the electrical parameters i.e., voltage, current, power, power factor, lumens and frequency, voltage and current waveforms, and the luminous flux (lumen). The effect of input voltage variation on lumens output and luminous efficacy of lamps, and variation in lumens due to difference in temperatures are to be studied. The effect of temperature variation caused by heating of the lamps and corresponding effect on lumens output and luminous efficacy of lamps are to be studied. A comparison between incandescent lamp, CFL, Fluorescent tube and LED bulbs is to be studied. 2. PROCEDURE: (i) Keep the working table clean. (ii) Check the testing panel switches and digital displays of various parameters in the  photometric testing panel. (iii) Make and check the circuit connections by patch cords between the photometric sphere, photometric testing panel and Variac. (iv) Check supply voltage (V) and frequency (Hz) of the supply. (v) The Variac is adjusted to supply the potential coil at voltages between 190V and 240V with a step of increment of 10V. (vi) Start the experiment and keep records of times (minutes)and various (vii) The window of the photometric sphere should be properly closed to avoid flux leakage from the photometric sphere. (viii) Note the various readings as tabulated on a time scale and Draw the performance characteristics of incandescent bulb, and Fluorescent tube. (ix) Make a comparative assessment on luminous efficiency for the light sources used. (x) Calibration of the Lumen Meter in the Photometric Panel (Fig.5) - An NPL tested LED bulb can be used for calibration of the Lumen Meter present in the Photometric Panel. 3. Nameplate readings of the Bulb and Calibration: Nameplate Readings of the tested Readings after Percentage Bulb Calibration error Voltage (V) Current(A) Watt (W) pf Luminous flux (lumen) Case-I Incandescent Lamps ( 60 W PHILIPS Bulb to operate at 240V- 190 V Supply voltages) Time Volt(V) I(A) Lumens PF watt(w) VA Temp Freq Efficacy (mins) (°C) (Hz) (lm/w) t 240 50.0 t+5 220 t+10 200 t+15 180 t+20 160 t+25 140  Case-II CFLS (Bajaj5 W CFL, 220-240V,50Hz, 210 Lumens, 0.85pf and 6500 °K ( to operate at 240V-190V supply voltages) Time Volt(V) I(A) Lumens PF watt(w) VA Temp Freq Efficacy (mins) (°C) (Hz) (lm/w) t+30 240 t+35 220 t+40 200 t+45 180 t+50 160 t+55 140 Case-III LED (Philips 8W LED bulb, 0.5 pf,720 lumens( to operate at 240V - 190V supply voltages) Time Volt(V) I(A) Lumens PF watt(w) VA Temp Freq Efficacy (mins) (°C) (Hz) (lm/w) t+60 240 50.0 t+65 220 t+70 200 t+75 180 t+80 160 t+85 140 Case-IV Fluorescent tube(18W, 2ft long, 220-240V,50Hz, …… Lumens, ….. pf (to operate at 240V - 190V supply voltages) Time Volt(V) I(A) Lumens PF watt(w) VA Temp Freq Efficacy (mins) (°C) (Hz) (lm/w) t+90 240 50.0 t+95 220 t+100 200 t+105 180 t+110 160 t+115 140 4. PRECAUTIONS (i) Good electrical contacts are necessary to make total luminous flux and electrical operating parameter measurements meaningful. Good quality and clean lamp socket can be used. (ii) An interior coating reflectance should be of 90% to 98 % for the sphere wall, depending on the sphere size and usage of the sphere. (iii) In total luminous flux measurements, the most obvious systematic error is the calibration uncertainty and it is to be minimized by taking appropriate measures. (iv) Flux losses through the Sphere’s port openings should be minimized. (v) Regulated power supply for operating the lamps during photometric testings is to checked. 5. CONCLUSION The performance characteristics of the light sources (viz. bulbs/FT) including variation of luminous flux at variable voltage, and luminous efficacy are studied meticulously and the results of the experimental observations are captured.