01-12-2012, 11:54 AM
ENERGY CONSERVATION IN ELECTRICAL DRIVES
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INTRODUCTION
With the discovery between 1845 and 1847, of the principle of ‘conservation of energy’, the importance of energy for human life and progress was recognized and scientists gave energy the romantic name “The Queen of the World”. In India from ancient times the importance of the energy was known. As perfectly said in BHAGWADGITA,
“This world is full of energy. It cannot be destroyed. & no one is able to do so!” It is very common that energy cannot be destroyed. The phenomenon which reduces the quantity of energy (like from one end to other end of the cable) is termed as “LOSS”. On the other hand an attempt made for the saving of energy is “conservation”. Thus loss and conservation are the two sides of the coin. It is very important that whenever this coin is tossed we must get conservation side up.
NEED OF ENEGY CONSERVATION
Most of the consumers of electricity in the older industries are not aware of energy conservation. It must be adopted immediately due to following reasons:
• Power scenario in India is becoming more and more alarming. The gap in supply and demand is increasing-present gap being 7% and peak demand storage being about 12%.
• The average cost of power generation has increased to Rs.4crore/MW and T & D losses including power theft remain uncontrollable at unacceptable high level of around 35% to 40%.
• The losses are occurring in small AC motors particularly agricultural pump motors which no. several million and are gulping thousand of megawatts due to shear carelessness.
Energy efficient motor (EEM) :-
EEM consume less electricity as compare to standard motor for any given load . High efficiency are obtained due to belter material, longer core length low loss core laminations. A graph of full load efficiency of EEM & standard motor is as shown in fig I. Cost of EEM higher 15 to 30 % than cost of standard motor. EEM operate at higher power factor than the standard motor. Therefore less amount is required to be spending on p.f. correction equipments or less p.f. penalty charges. .If full load operation is not required all the time, EEM give im¬proved saving over standard motor.Considering all the benefits of EEM. though the cost of EEM is moder¬ately high and even if payback preferred over standard motors no energy using appli¬ance should bought purely on the basis of capital cost.
Under loading OR Over sizing: -
While employing an electric motor for particular application softy margins are provided at every step by a designer and engineer a manufacture and user which adversely affect the power factor for the same load the over sizing motor will take more currently as compare to proper size. Therefore always be avoided and correct size motors should be selected.
Power factor control: -
Induction motor draws more lagging current under no load light load conditions. This result in poor power factor which leads to increase in the current and power loss this leads reduction in power factor this reduced switch gear capacity voltage regulation becomes poor. This entire problem can be overcome if capacitor or power factor controller is installed.
(1) Power factor is improved,
(2) Reduction in reactive power.
(3) Magnitude of no load and full load current are reduced which will be reduced losses and indirectly following Advantage has been made,
(i) Efficient use of electricity,
(ii) Less liability of cable.
(iii) Improve voltage profile on load side.
(iv) Minimize wear and tear of switching because of lesser arcing energy dissipated.
Agriculture sector:
Electrical motor is a component of the agriculture pump set. They are mainly used for drawing water from wells and there are two primary types: surface and submersible. They are operated at varying water levels throughout the day and from season to season. Consequently electric motor is subjected to varying loads. This operational strain on the pump motors are adding to efficiency problem. As the no. of electric pumps is in large volume, it is necessary to take into consideration this fact.Along with all technical improvements in motor design at the manufacturing level following market level suggestions should be considered:
Proper guidance and assistance to farmer:
Farmers tend to buy pumps with oversized motor to counter the low voltage power supply problem. Farmer requires quick response for service and repair. Local electrician or mechanics provide this service and act as a broker at the time of new purchases. The dealer acts as a technical consultant, who has no technical knowledge. Energy efficiency is not a consideration. Thus government must give them proper guidance through information channels about maintenance and purchasing of pumps.
Incentives for energy conservation:
The major factor driving the lack of interest in energy efficient motors is the heavily subsidized power tariff for the agricultural sector. Power supplied for that is not metered, but charged on the basis of connected load, hence no incentives for efficiency. Thus after taking care of farmer’s financial position, new scheme must be launched which will be beneficial to farmer and will save energy as well as increase efficiency. There are advanced agriculture pumps available in the market which are useful for farmers and also can save energy. They are as follows:
Sewage/Mud Pumps
They are quick automatic self priming action with back-pull out design for easy-maintenance with non-clogging impeller to handle suspended solids. Easily portable with trolley arrangement suitable for motor as well as engine drive compact monoblock version also available along life due to replaceable wearing parts grease lubricated deep groove ball-bearing.
PVDF Molded Pumps
Leakless recommend the Teflon Lined and PVDF Moulded Pumps for severe Industrial applications involving highly corrosive liquids like HF, HCL, FeCL3, HNO3, CH3COOH, CrO3 etc. with high temperature. These pumps are available in Centrifugal, Self-priming, Monoblock, with special designed Mechanical Seal to ensure reliability.
PSF Self Priming Centrifugal Pump
Self priming centrifugal pumps are in both close-coupled and back pull-out design. A non-return valve acts to retain sufficient liquid in the casing to assure fast & reliable priming, repriming and air-handling capabilities. The pump comes with the facility of reprimeing automatically once initially primed the pump. Impellers are semi-open type designed for maximum efficiency and repriming capabilities to achieve better suction lift characteristics. All rotating parts are dynamically balanced results in vibration free operation – longer life of bearings – low noise. In close-coupled design, motor designed for wide voltage range hence no fear of burn out due to voltage fluctuation. In back pull-out design, the entire sub-assembly can be removed without disturbing the pipe work and the driver. There is no need for any realignment after reassembling.