Measures for Energy Conservation in Electrical Drives:
Following Measures for Energy Conservation in Electrical Drives:
- Use of efficient semiconductor converters.
- Use of efficient motors.
- Use of variable speed drives.
- Energy efficient operation of drives.
- Improvement of power factor.
- Using a motor of right rating.
- Improvement of quality of supply.
- Use of single- to three-phase semiconductor converters in rural applications.
- Regular and preventive maintenance of motors, transformers and coupled equipment.
Using a Motor of Right Rating:
Most consumers tend to select a motor power rating much higher than necessary. In their opinion this ensures safe and reliable operation of the motor and in some applications provides flexibility of adding some more load. This oversizing of motor has several disadvantages such as higher motor cost, higher power modulator cost, higher installation cost, lower power factor and efficiency, and higher losses. Thus, oversizing the motor is not the correct approach. Adequate and careful analysis must be done to calculate motor rating for a given application. Then from among the commercially available ratings, the next higher rating, which is quite close to the calculated rating, must only be selected.
Improvement of Quality of Supply:
Due to inadequate reactive power compensations, the motor terminal voltage varies in wide limits. In order to avoid low voltages, substation transformers are often set for higher voltages. Under light load conditions, overvoltage conditions are produced. Motors and transformers designed for normal voltage operate under considerable saturation and losses. Sometimes, the transformers and motors are designed so that they do not saturate at high voltage conditions. When designed so liberally, at normal voltage they operate at a low flux level and their capabilities are not fully utilised. Situation is similar to operating motor at reduced voltage. In case of induction motor, the machine should carry larger current to produce same torque. In order that the machine develops its rated torque, the winding current ratings have to be higher.
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 are furnaces and welding machines is another common problem.
Use of Single- to Three- Phase Semiconductor Converters in Rural Applications
Villages situated for away from cities usually receive only single phase supply because of economic reasons. Single phase motors are very inefficient compared to three-phase motors, and therefore, their use should be restricted to low power ratings (up to 1 kW rating). For higher kilowatt ratings, three-phase motors should be preferred. Presently, for ratings of the order of 10 to 25 kW, three-phase motors are employed. Conversion from single-to three-phase voltages is obtained by passive circuits which are inefficient, expensive, heavy and bulky. Use of semiconductor converters for conversion from single-to three-phase voltage can help in saving energy in two ways. First, energy saving can be affected in conversion itself because semiconductor converters are very efficient. Secondly, three-phase motors can be used for several other applications where single phase motors are presently in use.
Regular and Preventive Maintenance of Motors, Transformers and Coupled Equipment:
Friction losses in the motors and electrical 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 oil are some of the steps that could be taken.