Role of capacitors in energy-efficient systems
An article on role of capacitors in energy efficient systems.
Nowadays there is increasing awareness about saving energy and utilising the available energy efficiently by employing energyefficient devices. Thus, there is a trend to convert conventional systems to energyefficient systems. A capacitor, which improves the power factor of the system, forms an integral part of the energy efficient system. Industry is rapidly changing over to energy efficient drives/devices such as DC drives, variable speed AC drives, energyefficient lamps, UPS, etc.
Though these devices facilitate the use of energy efficiently, they reduce the power factor of the system and inject harmonics in the system. These problems further gives rise to another problems and ultimately there is reduction in the overall efficiency of the system.
DEVICES AND PROBLEMS CAUSED BY THEM: 1. DC drives:
DC drives are used as they give better efficiency than that of AC drives. Also the speed control of DC drive is easy. AC supply is converted into DC supply using converters. Converters reduces power factor and introduce harmonics. AC------> Converter------> DC2. Frequency converters :
These are used to control the speed of AC drives. First AC supply is converted into DC supply which is again converted into AC with different frequency. This also reduces the power factor and introduces harmonics. AC (50Hz) ------> DC(Using Converter)------> AC (Using Inverter) (Variable frequency)
3. Electronic items:
For accurate and automatic control, there is an increase in use of electronic controls Also use of computers has increased. All these electronic items require switched mode power supply (SMPS) which draws current over a part of each half cycle. This reduces the power factor.
4. Energy efficient lamps:
These lamps draw an almost instantaneous current over a short portion of the voltage wave. This reduces the power factor.
All these devices form what is called as nonlinear load, which not only causes the problem of low power factor but also problem of harmonics.
POWER FACTOR CONTROL
In an electrical distribution system, low power factor and harmonics cannot be tolerated as it reduces the overall efficiency of the system and also affects the working of other devices. To improve the power factor, the use of capacitor is essential. Where harmonic level is high only capacitor does not serve the purpose and use of power factor correction capacitors along with the harmonic filter becomes essential. Reactive power compensation is very important as it not only improves the efficiency of the system but also reduces the penalty for low power factor
BENEFITS OF HIGH POWER FACTOR:
Reduction in power loss, improvement in efficiency of the system
CAPACITOR EFFICIENCY & INSTALLATION NORMS
- Reduction in KVA rating of equipment's, better utilisation of equipment
- Better voltage profile
- Less voltage fluctuations
- Higher stability
Capacitor itself is an energy-efficient product as it has low power loss. Its efficiency can be as high as 99.9%. In addition to this, capacitors has low initial cost, flexibility in choosing rating, compact size, easy installation, less maintenance etc.