Boiler

General Description:

To obtain the best possible economic advantage from electric power both the generating plant and consumers plants should be operated at high efficiency. To achieve this it is essential to have a high power factor throughout the system.

Most a.c. electric machines draw from the supply apparent power in terms of kilovolt-amperes (KVA) which is in excess of the useful power measured in kilowatts(KW) required by the machine. The ratio of these quantities

Useful power/Apparent power or KW/KVA =Power factor (cos φ)

is known as the power factor of the load and is dependent upon the type of machine in use. A large proportion of the electric machinery used in industry has an inherently low power factor, which means that the supply authorities have to generate much more current than is theoretically required. In addition, transformers and cables have to carry this extra current. When the overall power factor of generating station’s load is low, the system is inefficient and the cost of electricity correspondingly high. To overcome this, and at the same time ensure that the generators and cables are not overloaded with wattles current, the supply authorities often offer reduced terms to consumers whose power factor is high or impose penalties for low power factor.

Reductions in power costs can be made by taking advantage of these special terms.

Definition: The power factor of a load is defined as the ratio of active power to apparent power, i.e. KW:KVA and is referred to as cos φ. The closer cos φ is to unity, the less reactive power is drawn from the supply.