1. UNIT VI ILLUMINATION, HEATING & WELDING

2. Q. 1 Explain the different factors to be considered while designing the lighting scheme? Q. 2 What is induction heating? State the factors affecting choice of frequency in induction heating. Q. 3 Estimate the number and wattage of lamps which would be required to illuminate a workshop space 60 ×15 m by means of lamps mounted 5m above the working plane. The average illumination required is about 100 Lux. Coefficient of utilization is 0.4; Luminous efficiency is 16 Lumens / watt. Assume a space- height ration of unity and candle power depreciation 20%. Q. 4Discuss the factors affecting design procedure of good lighting scheme. Q. 5What is polar curve? How it is useful for illumination engineer. Q. 6It is desire to illuminate a drawing hall with an average illumination of about 250 Lux. The area of the hall is 30m× 20 m. The Lamps are to be fitted at 5m height. Find the number and the size of incandescent lamp required for an efficient of 12 lumens/ watt. Utilization factor is 0.4 and maintenance factor = 0.85

3. Q. 7Explain briefly the various method of lighting calculation. Q. 8What is resistance welding? What is its limitation? Q. 9Describe the method of arc welding. Q. 10 A class room of size 30m × 30 m is to be illuminated with 75 lux. The lamps are required to be hung 5 meter above the working plane. Assume Space–Height ration between 0.9 to 1.0. Utilization factor of lamp = 50%, Depreciation factor = 80%, Lamp efficiency = 15 Lumens/watt. Calculate the number & rating of lamp. Q. 11Explain different types of lighting scheme. Q. 12Define & Explain following terms :- i)Glare ii)Space- Height Ratio iii)Depreciation factor iv)Candle Power. v)Utilization factor vi)Waste light factor

4. Q. 13 A machine shop 30 m long by 15m wide is to have general illumination of 150 mm on working plane provided by lamps mounted 5m above it. Assuming coefficient of Utilization of 0.55 design suitable installation : i)Using filament lamps ii)Using slandered 80 watt fluorescent lamp. Q. 14Write short note on street lighting.

5. INTRODUCTION: Light Natural light Artificial light NATURE OF LIGHT Light is a form of radiant energy from a hot body which produces the visual sensation upon the human eye denoted by Q lumen-hours and is analogous to watt-hour incandescent bodies are the sources of light light emitted by such bodies depend upon the temperature of bodies Heat energy is radiated into the medium by a body which is hotter than the medium surrounding it

6. NATURE OF LIGHT heat of the body can be classified as red-hot or white-hot While the body is red-hot the wave-length of radiated energy will be sufficiently large and the energy available is in the form of heat When the temperature increases the body changes from red-hot to white-hot state wavelength of energy radiated becomes smaller and enters into the range of the wavelength of light hot bodies emit heat as well as light energy, the velocity of these being to 3x 10 8 m/s. light wave have wavelengths varying from 0.00075 mm to 0.0004 mm.

7. NATURE OF LIGHT The wavelength of light is usually expressed in Angstrom (Ǻ ) i.e. 1 Ǻ = 10 -10 m The ratio of the energy emitted by body in the form of light to the total energy emitted by body is known as the ‘radiant energy’ of the body which depends upon the temperature the wavelength of radiant energy and higher the radiant efficiency radiant efficiency will be maximum when the temperature of the body will be such that the wavelength of the shortest wave radiated by the body is 0.0004 mm (4000 Ǻ).

8. TERMS USED IN ILLUMINATION Light. Form of radiant energy from a hot body which produces the visual sensation upon the human eye. It is usually denoted by Q, expressed in lumen-hours and is analogous to watt-hour. Luminous Flux. The total quantity of light energy emitted per second from a luminous body. represented by symbol F and is measured in lumens. The conception of luminous flux helps us to specify the output and efficiency of a given light source. Luminous Intensity. in any given direction is the luminous flux emitted by the source per unit solid angle, measured in the direction in which the intensity is required. It is denoted by symbol I and is measured in candela (cd) or lumens per steradian. Lumen. It is the unit of Luminous Flux and is defined as the amount of Luminous Flux given out in a space represented by one unit of solid angle by a source having an intensity of one candle power in all directions. i.e. Lumens = = Candle power x solid angle = CP x

9. Candle Power. It is defined as the number of lumens given out by the source in a unit solid angle in a given direction. It is denoted by CP. Illumination. When the light falls upon any surface, the phenomenon is called the illumination. It is defined as the number of lumens, falling on the surface, per unit area. denoted by a symbol E and is measured in lumens per square meter or lux or meter-candle. If luminous flux of F lumens falls on the surface of area A, then the illumination of that surface is E = lumens/m 2 or lux (lx) Lux or Metre-Candle. It is the unit of illumination and is defined as defined as the amount of luminous flux falling per square meter on the surface which is everywhere perpendicular to the ray of light from a source of one candle power and one meter away from it.

10. Foot-Candle. It is also the unit of illumination and defined as the flux falling per square foot on the surface which is everywhere perpendicular to the ray of light from a source of one candle power and one foot away from it. i.e. 1 Foot-candle = 1 lumen/ft 2 =10.76 meter-candle or lux Candela. It is also the unit of luminous intensity. It is defined as1/60 th of luminous intensity per cm2 of a black body radiator at the temperature of solidification of platinum (2043 K). Mean Horizontal Candle Power (MHCP). It is defined as the mean of candle power in all directions in the horizontal plane containing the source of light Mean Spherical Candle Power (MSCP). The mean of candle power in all directions and in all planes from the source of light is termed as Mean Spherical Candle Power Mean Hemispherical Candle Power (MHSCP). It is defined as the mean of candle power in all directions above or below the horizontal plane passing through the source of light. Reduction Factor. Reduction factor of source of light is the ratio of its mean spherical candle power to its mean horizontal candle power.

11. Lamp Efficiency. It is defined as the ratio of the luminous flux to the power input. It is expressed in lumens per watts. Specific Consumption. It is defined as the ratio of the power input to the average candle power. It is expressed in watts per candela. Brightness or Luminance. It is defined as the luminous intensity per unit projected area of either a surface source of light or a reflecting surface and is denoted by L. Glare. It may be defined as the brightness within the field of vision of such character as to cause annoyance, discomfort, interference with vision or eye fatigue. Space-height Ratio. It is defined as the ratio of horizontal distance between adjacent lamps and height of their mountings. Utilization Factor or Coefficient of Utilization. It is defined as the ratio of total lumens reaching the working plane to total lumens given out by the lamp.

12. Maintenance Factor. The ratio of illumination under normal working condition when the things are perfectly clean is known as maintenance factor. Depreciation Factor. This is merely \the inverse of the maintenance factor and is defined as the ratio of initial metre-candles to the ultimate maintained metre-candles on the working plane. Its value is more than unity. Waste Light Factor. Whenever a surface is illuminated by a number of sources of light, there is always a certain amount of waste of light on account of overlapping and falling of light outside the edges of the surface. The effect is taken into account by multiplying the theoretical value of lumens required by 1.2 for rectangular areas and 1.5 for irregular areas and objects such as statues, monuments, etc. Absorption Factor. In the places where atmosphere is full of smokes fumes, such as in foundries, there is a possibility of absorption of light. The ratio of total lumens available after absorption to the total lumens emitted by the source of light is called the absorption factor. Its value varies from unity for clean atmosphere to 0.5 for foundries. Beam Factor. The ratio of lumens in the beam of a projector to the lumens given out by lamps is called the beam factor. This factor takes into account the absorption of light by reflector and front glass of the projector lamp. Its values vary from 0.3 to 0.6.

13. Reflection Factor. When a ray of light impinges on a surface it is reflected from the surface at the angle of incidence, A certain portion of incident light is absorbed by the surface. The ratio of reflected light to the incident light is called the ‘ reflection factor ’. It is always less than unity. Solid Angle. It is the angle generated by the surface passing through the point in space and periphery of the area. Solid angle is denoted by expressed in steradians and is given by the ratio of the area of the surface to the square of the distance between the area and point

14. GOOD LIGHTING SCHEME REQUIREMENT 1. Illumination Level:- depends upon a)Size of object – smaller the size of object, greater will be he illumination required for its proper perception, b)Distance from the observer – greater the distance from the observer greater will be he illumination required for its proper perception, c) Contrast between the object and back ground – greater the contrast between the colour object and back ground, greater will be illumination required to distinguish the object properly. Objects which is moving required more illumination than those for casual work and stationary object. 2. Uniformity of Illumination:- The human eye adjust itself automatically to brightness within the field of vision. If there is a lack of uniformity, pupil or iris of the eye has to adjust more frequently and thus fatigue is caused to the eye and productivity is reduced. 3. Colour of Light:- The appearance of the body colour entirely depends upon the colour of the incident light.

15. 4. Shadow:- In lightning installations, formation of long and hard shadows causes fatigue of eyes and therefore is considered to be a short-coming. Complete absence of shadows altogether again does not necessarily mean an ideal condition of lighting installations. 5. Glare:- It may come directly from the light source or it may be reflected brightness such as from a desk top, nickeled machine parts. 6. Mounting Height:- The mounting height will largely be governed by the type of the building and type of lighting scheme employed. 7. Spacing of Luminaires:- Correct spacing is of great importance to provide uniform illumination over the whole area and thus do away with comparatively dark areas which are so often found when the fittings are badly spaced. 8. Colour of Surrounding Walls:- The illumination in any room depends upon the light reflected from the walls and ceiling. While walls and ceiling reflect more light as compared to coloured ones.

16. LAWS OF ILLUMINATION There are two laws of illumination: i) Law of inverse squares and ii) Lambert ’ s cosine law Inverse Square Law

17. ii) Lambert ’ s cosine law Very often the illuminated surface is not normal to the direction of light as AC in fig. but inclined as AB. The area over which the light is spread is then increased in the ratio and the illumination decreases in the ratio Lambert’s Cosine Law expression for the illumination E = According to this law the illumination at any point on a surface is proportional to the cosine of the angle between the normal at that point and the direction of luminous flux

18. POLAR CURVES used to determine the mean horizontal candle power (m.h.c.p.) and mean spherical candle power (m.s.c.p.) used to determine the actual illumination of a surface. No practical type of lamp gives light uniformly distributed in all directions because of its un-symmetrical shape. It is often necessary to know the distribution of light in various directions. The luminous intensity in all directions can be represented by polar curves. If the luminous intensity in a horizontal plane passing through the lamp is plotted against angular position, a curve known as horizontal polar curve is obtained. If the luminous intensity in a vertical plane is plotted against angular position, a curve known as vertical polar curve is obtained. The typical polar curves for an ordinary filament lamp are shown in fig.

19. Polar curve for Horizontal Plane Polar curve for Vertical Plane

20. Mean spherical candle power can be determined from the vertical polar curve by Rousseau ’ s construction. Rousseau ’ s construction: A semicircle of any convenient radius is drawn with the pole of the polar diagram as centre. The line CD is drawn equal and parallel to the vertical diameter YY ’. Now this line CD ordinate equal to corresponding radius on the polar curve are set up such as BD=OK, and so on. The curve obtained by joining the ends of these ordinates is known as Rousseau ’ s curve. The mean ordinate of this curve gives the m.s.c.p. of the lamp having polar curve given in the fig. Rousseau’s construction The mean ordinate of the curve =

21. Types of Lightning System

23. METHODS OF LIGHTING CALCULATIONS

24. FACTORY LIGHTINGS

26. METHODS OF HEATING Electric heating is any process in which electrical energy is converted to heat. Common applications include space heating, cooking, water heating and industrial process Advantages of electric heating over other systems of heating such as coal, oil or gas heating are  Economical  Cleanliness  Absence of flue gases  Ease of control or adaptation  Automatic protection  Upper limit of temperature  Special heating features  High efficiency of utilization  Better working conditions  Safety  Heating of non-conducting materials

27. CLASSIFICATION OF ELECTRIC HEATING classified into two categories as Power frequency heating and High frequency heating Power frequency heating Power frequency heating Power frequency heating can be further classified as Resistance heating and Arc heating. Resistance heating:-It can be further classified as i)Direct resistance heating:- ii)Indirect resistance heating:- iii) Infrared or Radiant heating:-

29. Dielectric Heating In this method of electric heating use of dielectric losses is made to heat the non-metallic materials. Non-metallic material to be heated place between two metal electrodes across which a high voltage having high frequency is applied, the heat is developed owing to the dielectric losses taking place.

30. CLASSIFICATION OF WELDING METHODS A. Plastic Welding or Pressure Welding B. Fusion Welding or Non-Pressure Welding USE OF ELECTRICITY IN WELDING 1.RESISTANCE WELDING Butt Welding: It is of two types (a) upset butt welding which is preferred in production machines and (b) flash butt welding is used for welding chains, rail ends, rolled sections, shaft axles etc. 3.1.2 Spot Welding: By definition,spot welding is a form of resistance welding in which the parts and pieces are joined in spots, accompanied by heated relatively small sections of the parts and pieces between suitable electrodes under pressure It is usually used for joining or fabricating sheet metal structure as it only provides mechanical strength and is neither air tight nor water tight.

31. * Projection Welding: It is a modified form of spot welding. In this process the current and pressure are localised at the weld section by the use embossed, machined or coined projections on one or both pieces of the work. This type of welding is usually employed on punched, formed or stamped parts, where the projections automatically exist. * Seam Welding: It can be defined as a series of continuous spot welds. This process is employed for making a continuous joint between two overlapping pieces of sheet metal. Seam Welding is employed for welding pipes, conduits, tanks transformers, refrigerators, gasolinetanks, air crafts and various types of containers. * Percussion Welding: This is a recent development in the field of welding which depends on the arc effect for heating and not on the resistance. This is a self-timing spot welding method. In this process a current impulse is obtained by the discharge from a capacitor or from a magnetic field. It is employed for welding satellite tips to tools, copper to aluminum or stainless steel, silver contact tips to copper.

32. ARC WELDING arc welding is that process in which the pieces of the metal to be welded are brought to the proper welding temperature at point of contact by the heat liberated at the arc terminals and in the arc stream so that the metals are completely fused into each other, forming a single solid homogeneous mass, after it solidifies Carbon Arc Welding: Metal Arc Welding: Atomic Hydrogen Arc Welding: Inert Gas Metal Arc Welding: Submerged Arc Welding: