Category Archives: Electrical

Introduction to Solar Power Technology

Solar Power is conversion of sunlight to electricity, directly either using (PV) Photovoltaic or indirectly using (CSP) concentrated solar power. Systems of concentrated solar power use mirrors or lenses and tracking systems for focusing large sunlight area to small beams. Photovoltaic converts light to electric current by utilizing photovoltaic effects. Photovoltaic was solely initially used as electricity sources for medium and small sized applications. This is from calculators powered by 1 solar cell to homes remote being powered by rooftop off-grid PV system. As costs of solar electricity falls, numbers of grid connected PV solar systems have grown to millions. Utility scaled solar power stations with megawatts in hundreds are built. PV solar is rapidly becoming low carbon, inexpensive technology for harnessing renewable energies from Sun.

Emerging technologies after photovoltaic cell (PV cell) or solar cell: Concentrator photovoltaic (CPV): This system employs sunlight being concentrated onto surfaces of photovoltaic for purposes of electrical power productions. Opposite to conventional PV systems, it uses curved mirrors and lenses for focusing sunlight to small, but too much highly efficient multi- junction solar cell. Solar concentrators of many varieties are used. These are mounted often on solar trackers for keeping focal points on cells with movement of sun across sky. Luminescent Solar Concentrators plus PV solar cell is regarded as CPV system. CPV are useful because they improve PV solar panels efficiency drastically. Floatovoltaics: This is emerging form of the PV systems which floats on surfaces of tailing ponds, irrigation canals, quarry lakes and water reservoirs. This system in turn reduces requirement of land area valued and drinking water saved. This water could be lost by means of evaporation. Then there is showing of high efficiencies of solar energy conversions. This is as panels have been kept at cool temperatures than their presence on land. Hybrid Systems: This combines CSP and CPV with each other or with different forms of generations like biogas, diesel and wind. Generation’s combined form enables systems modulating power outputs as demanding functions or reducing at least fluctuating solar power natures and consumption of fuel non-renewable. These hybrid systems are often found on islands.

CSP/CPV system: Novel solar CSP/CPV hybrid system is proposed. It combines concentrator photovoltaic with non-PV technologies of concentrated solar powers. This is called also concentrated solar thermal. ISCC system: There is combination of CSP with gas turbines. In this, 25 megawatt CSP parabolic trough arrays supplement much large 130 megawatt combined turbine cycle gas plant. PVT system: This is Hybrid PV/T system. It is called Photovoltaic Thermal Hybrid Solar Collectors. This converts solar radiations to electrical and thermal energy. This system combines Solar PV modules with solar thermal collectors in complementary ways. CPVT system: It is Concentrated Photovoltaic Thermal Hybrid system being same as PVT system. This utilizes concentrated photovoltaic (CPV) in place of conventional PV technologies. This combines it with solar thermal collectors. PV diesel system: This combines PV system with diesel generator. Combination with different renewables has been possible that includes wind turbines. PV-thermoelectric system: Thermovoltaic, thermoelectric devices convert temperature differences in between dissimilar materials to electric currents. Solar cells use high frequency radiation parts only. Low frequency heat energy is wasted. Plenty of patents regarding use of the thermoelectric devices in solar cell’s tandem have been filed. Idea is increasing efficiencies of combined thermoelectric/solar system for converting solar radiations to useful electricity.

Parabolic trough in turn consists of linear parabolic reflectors which has concentration of light to receivers being positioned through focal line of reflector. Receiver is tube being positioned just right above middle of parabolic mirrors. This is filled with working fluids.

Radial Feeder Protection: Overview and Configuration

Protective relay function is causing quick removals from services of power system elements that suffer short circuits. There is starting of operation in abnormal manners which causes damage or holding up with operation effectively of rest system. Secondary functions of Radial Feeder Protection are indication provision of failure types. Automatic oscillograph and human observation records provide analysis of fault prevention effectiveness. This includes features of relay protection itself.

Radial distributions had had more potential for improving system performance of itself. This factor must be encouraged. Operating practices and system designs radially, however, are based normally on flowing of radial powers. This creates challenges specifically for introduction successfully. This ensures that the distribution generation does not degrade distribution system’s reliability, quality and safety. Relay operating application, principle and design have been presented as results from laboratory tests and simulation studies through computers. Analysis spectrally of current and voltage waves are made for extracting switching times of capacitor acceptable by observations of current and transient over-voltages. Solution of mal trips is dependent on lots of factors, but more importantly on immunities of protective relay. This is against impacts of non-fault transients.

Radial Feeder Protection’s configuration: Transmission line protection’s in turn presents plenty of relaying fundamental considerations. It applies to protection of different types of system protection. All electrical elements have unique problems to themselves. Concepts of selectivity, remote and local backup, protection zones, reliability, and speed and coordination being present in 1 or more protection of electrical apparatus is present in transmission line protection surrounding consideration. The transmission lines links also to connected equipment or adjacent lines. The transmission line protection is compatible with protections of all different elements. All this needs coordination of characteristics, settings and operating times. Protection of power system purposes is detecting abnormal or faulty operating conditions, thereby, initiating correct actions. Relays must have abilities of evaluating wide parameter varieties for establishing needed correct actions. A relay, obviously, cannot prevent faults. It’s most important purpose is detecting faults and taking needed actions for minimizing damages to equipment or to system. Most important common parameters reflecting fault presence are currents and voltages at terminals of apt zone boundaries or apparatus protected. Problems fundamentally in power system’s protection are defining a quantity which differentiates in between abnormal and normal conditions. These problems are compounded on facts that “normal” in present senses mean outside zone’s protection. Electrical power distribution is portion of infrastructure power delivery which takes electricity from high voltage, highly meshed transmission circuits. It delivers this to its customers. Lines of primary distribution are “medium-voltage” circuits. This is thought normally of as 600 V to 33 kV. At distribution substations, the substation transformer take incoming transmission levelled voltages, that is, 132 kV to 33 kV. This is stepped down to many distribution’s primary circuits. This fans out from substations. Close to all end users, the distribution transformers take primary distribution voltages. This is stepped down to low voltage secondary circuits, basically, 33 kV /11 V, different voltages can be utilized as well. From distribution transformers, distribution secondary circuits connect to end users in which connections are made at service entrances. Power system networks in turn consist of distribution circuits, relay, generators, transmission line, transformers, and circuit breakers. In case fault occurs on different system’s part, it must be detected quickly and then disconnected from system.

Reasons are 1st if fault is not quickly cleared then it shall cause interruption unnecessary of services to customers. 2nd rapid disconnection of apparatus faulted limits damage amounts to it. These prevent fault effects from spreading in different system parts. Back-up relaying has been employed for protection only against the short circuits.

Stepper Motor: Its Operation and Applications

Stepper motor is also called stepping motor or step motor. It is DC brushless electric motor which divides full rotations to equal numbered steps. Position of motor is then commanded for holding and moving at 1 of steps with no feedback sensor (open loop controller). This is that much long till motor is sized carefully for application with respect to speed and torque. Switched reluctance motors have been very larger stepper motors. This is with pole count reduced and closed loop commutated.

Stepper motor operation: Stepper motors different operates from brush DC motors. This rotates when voltages are applied to terminals. Stepper motors have effectively electromagnets multiple toothed being arranged about central gear shaped iron piece. Electromagnets have been energized by control circuits externally, for example, microcontrollers. For making turning of motor shafts, 1st one electromagnet is provided power. This makes teeth of gear attracted magnetically to teeth of electromagnet. Points when a tooth of gear is aligned like this to 1st electromagnet, then they are offset slightly from other electromagnet. When next electromagnets is kept ON and 1st kept OFF, then slight rotation of gear is there. This aligns next one. From this there is repetition of process. All slight rotations are known as step. This is with step’s integer numbers which makes full rotations. By this method, motor is turned by precise. Stepper motors do not continuously rotate. They rotate about in steps. 4 coils are there. It is 90 degree angles in between one another being fixed on stator. Connections of stepper motors are determined by ways interconnection of coils is there. Coils have not been connected together in stepper motors. Motors have 90 degrees rotation steps with coils energized in cyclic orders. This determines rotation direction of shaft. Motor working is done by switch operation. Coils have been activated in 1 second interval in series. Shaft rotates 90 degrees all times there is activation of next coils. Its lower torque speed shall vary directly with currents.

Application: There are security purposes: New products of surveillance for industry of security are there. There are industrial machines purposes: The stepper motors have been used in machine tooling, automated production and automotive gauges equipment. There are consumer electronics purposes: Stepper motors are utilized in digital camera’s automatic functions of zooming and focusing. There are medical purposes: Stepper motors have been utilized within respirators, fluid pumps, and machinery of blood analysis, medical scanners, digital dental photography and samplers. There are also applications like computer peripheral purposes and business machines purposes.

Control of stepper motor by clock pulses varying: Circuit of stepper motor controls is low cost simple circuit. This uses mainly low powered applications. Circuit consists of 555 timers IC as multi-vibrator stable. Timer output is thereby used as clocks for two 7474 dual “D” flip flops (U3 and U4) being configured as ring counters. When powers are switched on initially, only 1st flip-flop is set (that is, Q output of U3 at pin 5 shall be at logic “1”). Rest 3 flip-flops are reset (that is, Q output shall be at logic 0).upon receiving clock pulse, logic “1” output of 1st flip-flop becomes shifted to 2nd flip-flop (pin 9 of U3). So logic 1 output remains shifting in circular manners with all clock pulses. Outputs at Q of 4 flip-flops have been amplified by Darlington transistor arrays within ULN2003 (U2). This is connected to windings of stepper motor like black, orange, yellow and brown to 13, 16, 14 and 15 of ULN2003 and red to positive supply. Winding’s common point has been connected to +12V DC supply. This is connected also to pin 9 of ULN2003.

Passive and Active Sun Trackers

Sun trackers maximize solar panel system’s efficiency by 25% to 40% whilst tracking by motion of sun. Particularly, sun moves across sky from east to west. For making sun’s panel system efficient too much, system possibly should be perpendicularly positioned to rays of sun. In comparison to fixed PV sun’s systems, a solar tracking system increases array’s energy output by 30% to 55%. Along with tracking seasonally there is adjustment of sun’s panels on north south axis. Output of energy has been further increased. These sun trackers operate by minimization of incidence of light coming in and PV panel by itself. Totally 85% of nearly all installations commercially use sun trackers to little extents. Sun tracker systems make more than 1 MW of solar energies. Sun trackers use usually mounted ground solar arrays which allow walking underneath. It allows plants shades also for thriving under low intensified sunlight.

There are 2 types of sun trackers: One is passive. Other is active. A passive sun tracker essentially is too much slow vapour engine. These apparatus contains 2 reservoirs that contain Freon 12. This is connected by means of hydraulic cylinder or transfer hose. All containers of Freon 12 are shaded equal amounts. It allows setup containing more in 1 reservoir than different others whilst sun moves throughout sky from east to west. Tank with great sun exposures conducts collection of more heat thereby boiling more of Freon 12. There are differences in between low pressure and high pressure that retracts or extends pistons in hydraulic cylinders. When movement of piston is there, either it pulls or pushes solar panels with sun’s alignment. Freon 12 is very crucial and essential working fluid as because it has lowered boiling temperatures. It possesses head pressure enough for operating systems. But this head pressure is not sufficient enough for bursting system. It is non-explosive also and non-toxic relatively. It is available also in any place of world from any refrigeration shop. Passive trackers are operated thermally. They do not operate nicely in cold temperature areas or windy areas. Hydraulic dampers have been used for regulating sun tracker’s movements.

Active trackers have been mechanized for necessities and requirement of regular maintenance. Benefits and advantages of utilizing active trackers are that it has had been precise extremely in sun measurement. Trackers dual axes, track east and west movement of sun and changes seasonally along axis of south and north. Problem encountered by people whilst running active trackers are that they become unreliable. Reason is that maintenance regularly is needed for running and operating them. There has been presence of moving parts. These moving parts anytime can be operated electronically. There has been little performance issues also. Sun trackers are those devices which help in maximizing solar panel’s output. Sun’s movement from low east to low west all round the day is tracked by sun tracker. Depending on makeup, sun trackers are classified as passive trackers and active trackers. Passive trackers do not utilize electricity for operation. Freon 12 is utilized as low boiling point working fluid. This transfers weight within modules. This then rotates solar panels. Vacuum pumps are connected to Schroeder valves. This charges it by half-filled with Freon. 2 long transfer hoses of refrigerant have been used for connecting reservoirs of Freon to cylinders acting doubly. Hydraulic gears are inexpensively purchased. Special heed needs being paid to (CG) centre of gravity of system of sun tracker. High centre of gravity causes system swinging forth and back erratically. But low centre of gravity causes slow movement of system. Balancing of 2 Freon tanks must be done for proper operation.

Electric Cars

The invention of vehicles made a land mark in the history of human race. The evolution of vehicles from animal carts to motor vehicles made the travel convenient and easy for people. By 19th century the use of motor vehicles was popular. The illustrious and affluent class people used motor vehicles as a prestigious symbol. Among the vehicles motor cars were widely used. After industrialization the use of motor vehicles increased as result of usage of motor vehicles by the common man. Soon the use of vehicles became an integral part of people in modern time all over the world. Among the motor vehicles the motor cars were accepted by people irrespective of their class or standard in the society. Soon cars became a necessity of common man rather than a luxury of elite class. Different models of cars were introduced by car manufacturing companies all over the world.

The increase in the demand of new and innovative designs and models of cars made the car companies particularly world class car manufacturing companies to increase in the production of cars within short intervals in a year. Most of the motor cars work using fuels. Diesel and petrol are the most popular fuels used in motor cars. In most of the developed countries gasoline cars replaces diesel or petrol cars. During the 19th and earlier 20th century the introduction of electric cars also made a change in the history of cars. People of elite class preferred electric cars as they were not common in usage due to their expensive usage. The work pattern of electric cars is based on electric usage by storing electric energy in the batteries of the engine in electric cars. An electric vehicle or automobile is defined as a vehicle that use electric motor for propulsion unlike an electric car that use electricity that is stored in the battery of the car engine. During 1930’s the introduction of gasoline cars that had half reduced cost effect in comparison to the electric cars gave a declined graph in the use of electric cars.

After a long time of decline during early 1990’s and in recent years, electric cars regained demand among different class of people in the society. The adverse environmental impact created by fuel and gasoline vehicles gave a new perspective in the use of electric cars. Apart form the initial cost and expense the new battery technologies used in the modern cars resulted in the increased demand of electric cars today. The remarkable features of electric cars are their environmental friendly use that does not result in the air pollution like fuel or gasoline vehicles. They do not produce any carbon compounds like hydro carbon, carbon monoxide, ozone lead and other volatile compounds emitted from the motor vehicles. Another feature is its efficiency. Unlike motor vehicles with internal combustion engines that waste the fuel through heat during propulsion electric car motors converts the battery stored energy to drive the vehicle without emitting any pollutants. A typical electric car use 10-23 kilowatts per hour. The only drawback in the electric car is that 20% of the power consumption is used for charging the batteries. The risk of fire in the engine due to the overheating of batteries is another negative aspect in electric cars.

The safety measures in electric cars are done as per the standards of ISO 6469. The three major concerns regarding the safety measures taken in electric cars are onboard electrical energy storage in the battery, protection of person against electrical hazards and functional safety means and protection against failures.

The usage of electric car need to be promoted more in this modern era for its efficient function and less environmental damage features despite its heavy initial cost and expense.

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