In order to keep the manufacturing cost of a product minimum and make its price competitive in the market, it is necessary to minimize energy consumption at all stages of the manufacturing process including electrical drives. Energy conservation is also necessary because with the ever increasing demand need for electrical power can only be meet by conserving electrical power in addition to installation of new generating units. A major proportion of electrical power in a plant is consumed by electrical drives. Significant amount of electrical energy can be saved by the use of efficient and right type of electrical drives. This para briefly describes measure to be taken for conservation of energy in electrical drives which is an issu of great concern today.
The efficient operation of an electrical drives with minimum consumption of energy requires that the drive and the driven machinery or load operate efficiently. This cause for careful design of both electrical and mechanical system. Only those measures are considered here which can lead to an efficient operation of electrical drive system. Energy conservation in electrical drive is achieved by reduction of looses in its various parts. Certain measures for energy conservation in electrical drive system which are implemented in future.
ENERGY CONSERVATION IN ELECTRICAL DRIVES
INTRODUCTION
In order to keep the manufacturing cost of a product minimum and make its price competitive in the market, it is necessary to minimize energy consumption at all stages of the manufacturing process including electrical drives. Energy conservation is also necessary because with the ever increasing demand need for electrical power can only be meet by conserving electrical power in addition to installation of new generating units. A major proportion of electrical power in a plant is consumed by electrical drives. Significant amount of electrical energy can be saved by the use of efficient and right type of electrical drives. This para briefly describes measure to be taken for conservation of energy in electrical drives which is an issue of great concern today.
The efficient operation of an electrical drives with minimum consumption of energy requires that the drive and the driven machinery or load operate efficiently. This cause for careful design of both electrical and mechanical system. Only those measures are considered here which can lead to an efficient operation of electrical drive system. Energy conservation in electrical drive is achieved by reduction of looses in its various parts. Certain measures for energy conservation in electrical drive system which are implemented in future.
LOSSES IN ELECTRICAL DRIVES SYSTEMS
Energy conservation in electrical drives is achieved by reduction of losses in its various parts. Typical losses include the following :
Electrical transmission losses: These losses depends on the drive power factor and the harmonics in the line current.
Conversion losses in the power modulator (or converter): The semi-conductor converter usually has low conversion losses.
Electrical motor losses to convert electric power into mechanical power: These are determined by choice of motor (quality of its design and its selection of right rating ) and quality of supply (voltage variation, unbalance, frequency variations and harmonics.
Mechanical losses in the parts of the transmission system such as bearing , gears clutches and belts.
Losses in the load: Load is a machine required to perform a specified task such as fans, pump and train.
losses caused by throttling or by other means that control material flow by absorbing or bypassing excess output.
Mechanical transmission losses such as friction losses to move material from one location to another. Losses in pipe line carrying fluid is one such example.
MEASURES FOR ENERGY CONSERVATON IN ELECTRICAL DRIVES
Following measures can be adopted for energy conservation in electrical drives
Use of efficient motors.
Use of variable speed drives.
Improvement of power factor in electrical drives.
Using a motor of right rating.
Improvement of quality of supply
Regular and preventive maintenance of motors, transformers & coupled equipments.
These measures are explained in detailed as follows.
USE OF EFFICIENT MOTORS
Due to lack of awareness several consumers buy inefficient motors because they are cheaper this choice are highly uneconomical in the long run because of high charges of electricity. Usually the motors are inefficient due to three major factor:
Poor quality of lamination and insulation.
Use of less active material causing machine operation.
Poor mechanical design of bearing, clutches, gears and couplings.
Markets in India are flooded with substandard motors although there is no shortage of motors with good design. There is need for awareness among engineers, technicians and the other consumers to go for efficient motors.
USE OF VARIABLE SPEED DRIVES
Several drives are driven at constant speeds by induction or synchronous motors although operation at variable speed could lead to saving of substantial amount of energy such practice was adopted in the past because of non availability of efficient methods of speed control of induction and synchronous motors. Thus use of variable speed drives can lead to large saving of energy. Studies have shown that the energy saving ranges from 20%-40% and extra cost incurred in providing speed control can be recovered in period of 2-5 years. Considering that a no. of these drives have rating in megawatt range large amount of energy can be saved by the use of variable speed drives.
IMPROVEMENT OF POWER FACTOR
Due to wide spread use of elect. drives improvement of power factor has become an important issue. A good power factor
Decrease the copper loss in transformer, distribution cables, transmission line and other equipments, thus allowing considerable saving in energy consumption
Helps in stabilizing the system voltage
Reduce the load on transmission, distribution and transformer. Full utilization of substation and generating units.
Avoids large penalty often imposed on low power factor consumer by utilities.
Following methods are employing for improvement of power factor
[I].Overexcited synchronous motors
When connected direct on line a synch. motor runs at constant speed it draws leading reactive power when overexcited so it is one of the method of power factor improvement.
[II]. Static Capacitor
There are large number of applications where speed control is not required. Induction motors are widely used in these applications. Power factor of such drives can be corrected (improved ) by permanently connecting a fixed capacitor across the motor terminals.
USING A MOTOR OF RIGHT RATING
Most consumers tend to select motor power rating much higher than necessary. Over sizing of motor has several disadvantages such as higher motor cost, higher power modulator cost, higher installation cost, lower power factor & efficiency, & higher losses. Adequate & careful analysis must be done to calculate motor rating for a given application. Then from among the commercially available ratings the next higher ratings, which is quite close to the calculated rating, must only be selected.
IMPROVEMENT OF QUALITY OF SUPPLY
Due to inadequate reactive power compensation, the motor terminal voltage varies in wide limits. In order to avoid low voltage, substation transformers are often set for higher voltages. Under light load condition, over voltage conditions are produced. Another important problem is the unbalance of supply voltage. A small unbalance in voltage produces large unbalance in current and a large increase in losses. Sharp fluctuation of voltage due to loads like arc furnace and welding machines is another problem.
REGULAR AND PREVENTIVE MAINTENANCE OF MOTORS, TRANSFORMERS AND COUPLED EQUIPMENTS
Friction losses in motors and elect. losses in transformers and motors are reduced by regular and preventive maintenance of motors and transformers. Oiling of bearings, proper condition and setting of brakes, brushes etc. Proper condition of cooling fans and transformer oils are some of the step that could be taken.
CONCLUSION
Keeping in view the resources constraints new generation of capacity addition has limited scope. Trust areas of energy conservation, saving energy management and optimum utilization of existing installed capacities have vast potential for energy saving. These news technology are also helping to save the energy going to waste.
“Conserve Energy
Preserve Environment”
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