Electrical Engineering Technology

A light-emitting diode (LED) is a semiconductor device that produces light from electricity. LEDs last a long time and do not break easily (compared to incandescent lightbulbs). They can produce many different colors. They are efficient - most of the energy turns into light, not heat. (1) An LED is a type of diode that makes one color of light when electricity is sent through it in the expected direction (electrically biased in the forward direction). This effect is a kind of electroluminescence. (2)  The color of the light depends on the chemical composition of the semiconducting material used, and can be near-ultraviolet, visible or infrared. (3) The color affects how much electricity is used by the LED.  (4)  A white LED has either two or three LEDs inside, of different colors. Some white LEDs have one single-color LED inside (usually blue), combined with a phosphor that converts that single color to white. Ds are used in many places. They are the colored indicator ligh

         Totally enclosed Rising mains are with aluminium bus - bars or Copper bus-bars in suitable sections which are connected to make a vertical run. Each sections is provided with a number of wall straps for fixing  the  rising mains to the wall. The trunking consists of side channels of 14 SWG MS sheet and front and rear cover of 16 SWG to form totally enclosed metals clad construction.          The bus-bars of rectangular sections of wrought aluminium with a current density not exceeding 1.25 A per squire mm and are individually insulated with a non-deterioating material so as to prevent  any possibility of electrical fault due to presence of vermin. The aluminium bus-bars conform to IS 5082 -1969 grade 9-1 EQP. The total run in sectionalized and each section is fitted with a thrust pad to prevent the bus-bars from sliding downwards. Each section also has an expansion joint to take up expansion of that section.  2500 A bus -bars  Bus bar rising arrangement          Connections be

The LT Panel or Switch Board shall be preferably factory fabricated and of the approved manufacturer. The switchboard shall be fixed such that there shall be clear space of either less then 230 mm  or more then 762 mm in width behind the switchboard measured from the farthest outstanding part of any attachment of conductor and more then 1000 mm in width in front of the panel. There shall be a passage way from either end, both in front of or behind the panel, clear to height of at least 1829 mm. No apparatus shall project beyond and edge of the panel. No switch body shall be mounted within 25 mm of any edge of the panel and no holes, other then meant for fixing the panel shall be drilled within 13 mm of the edge of the panel. The various live parts shall be effectively screened by barriers of non- hygroscopic, non-inflammable insulating material or shall be so spaced chat an arc cannot be maintained between such parts and earth. All items of switch gear shall be readily accessible and a

Distribution substation Transformer like Indoor, outdoor and  Pole mounting, Three phase four wire system, Earth is connected in the Neutral and Earth Neutral meet point always Zero resistance . Three phase wires and neutral are brought out for onward distribution to a  particular area or locality.  The voltage between any of the three phase wire and neutral should be 230 volts if the  resistance between neutral and earth is zero . In  case the resistance between neutral and earth increase, the voltage across  phase  and  neutral  will also increase  accordingly thereby causing damage to electrical components bulbs etc.To counter this problem, the  joints  of  earth  wire  connecting  star  point  of  star winding and earth should be checked. If the joints, have gone rusty these  should  be  made again. The salt water should be poured into the earth pit  through funnel in the specially made concrete slabs or surface pit so that earth resistance is minimised.  Best  Neutral  connecte

There are several methods of applying artificial respiration,any one of which is good if applied properly. Following are some methods. Artificial Respiration  : (Method -1)  :    (a)  Lay the patient on his stomach with his face to one side. Free the neck from clothing and see           that passage of his throat is clear. Remove false teeth, tobacco etc. if any from the mouth.    (b) Kneel over him or at his side as may be convenient and place the palms of your hands flat in          the small of his back, with the thumbs nearly touching and the fingers spread out on each side           of the body under the lowest side of the ribs.            (c)   With arms staight, lean forward gradually over the patient bringing the wight of your body to                 bear on the patient for about a second Fig 1 .Next release all pressure for about 3 seconds               by swinging your body backward but without lifting yours hands from the patient Fig 2.       (d)  Repeat this application and

The human failure in handling the electrical  components or  repairing the  distribution  system  without switching off the supply,an electric current touches or flows through the body, it is known as an electric shock. The ultimate effect of electric shock on human body may be death.The result of electric shock on human body may be fatal  but it may be due to: (a)  Fibrillation of heat i.e. damaging the heart to small pieces causing the stopping of breathing. (b) Stopping of breathing action caused by blockade in the nervous system causing respiration. (c)  Local over heating action or burning of the body due to sparking.            The fibrillation of the hart is the most serious cause of death and there is no cure, although there  is a possibility of rescuing a man who has suffered by the later two cause. FACTORS ON WHICH INTENSITY OF ELECTRICAL SHOCK DEPEND           (i)  The current strength : It has been experienced that in alternating current of low frequency , the current  bet

This occurs due to either of the two reasons  i.e. firstly due to  poor  contact at a  jumper connection, Secondly, the supply being resumed to an installation without  taking care to put the neutral link back normal. Under such conditions, the neutral will assume a potential determine by the load in each of the phase because it is free to move anywhere within the triangle formed by the 3 phase potential ABC,and is no longer tied to the earthed star of the transformer.  (Star point of star winding of distribution transformer is solidly connection to keep the potential zero at the star point. The neutral conductor of 3 phase 4 wire distribution line is connected to star point of star winding of the distribution transformer). Such a neutral is called ' floating'.               Fig. A & B provide balanced load on  the three phase  i.e.230 volt between each phase and neutral.      Fig. C there are two equal load between line A & B. The floating neutral will now be at poi