What is Power Factor?
There has been and will continue to be a variety of measures developed to increase the efficiency of electrical systems and reduce electrical cost. Northeast Resource Group (NRG) Incorporated's Aerovox/Cornell Dubilier Power Factor Correction and Harmonic Suppression Systems employs the principals of low-voltage power factor correction to reduce an electric bill while actually increasing the electrical system capacity. This will allow commercial and industrial users of electricity to save appreciably on their power cost and to add new equipment without a costly electrical system upgrade.
The power used by commercial consumers has two components: Real Power, which is measured in KW, produces the actual work, while apparent power, which is measured in KVa, is the combination of real power and reactive power.
Reactive power is needed to generate the magnetic fields required for the operation of an inductive piece of equipment, sometimes called wattles power. Inductive electrical equipment, such as motors and transformers, must take from the electrical distribution system more current than is necessary to do the work involved. The ratio of real power to apparent power is called power factor.
This is usually represented as a percentage. In this case it would be 66%.
The power factor correction system lowers the electrical costs in three ways:
#1 In many areas of the country, electric rates include a charge for low power factor. This is done via the demand charge portion of the bill. The monthly demand is typically measured in both KW and in KVa. The power company takes the highest 15 to 30 minute demand measurement and calls it "peak demand": The billing demand is typically arrived at by taking a percentage of the peak KVa demand, (90% to 100%) and comparing it to the peak KW demand. The highest of the two figures becomes your billing demand.
NRG's power factor correction system, connected within the electrical distribution system, supplies the wattles power to the inductive loads making it unnecessary for the power company to supply it. This dramatically reduces the peak KVa demand figure. Savings are realized in reduced KVa demand charges.
#2 The second savings possible, through the use of NRG's power factor correction system, is in the form of increased capacity of the electrical distribution system. Installation of NRG's equipment to furnish the non-productive current requirements of the facility makes it possible to increase the plants connected load as much as 20% without a corresponding increase in the size of transformers, conductors and protective devices servicing the load.
Power factor correction is effective because the power company has to carry the reactive energy (KVAr) of facilities with a poor power factor they are now charging for it.
#3 The third area of savings is improved voltage and power loss reduction. Electrical system losses are also reduced by the reduction of total current and power that is delivered. This would result in less KWH consumption.
How Does the Power Factor Effect my Electric Bill?
By installing the power factor correction equipment in your system, you now supply your own reactive current which, in a perfect situation, will eliminate your KVa requirement (from a billing perspective) and return the facility to KW demand billing.
A typical industrial/commercial electric rate calculates a demand charge by taking 90% of the KVa demand figure and multiplying it times the demand rate.
Example: A power factor of .70
Let's assume the demand charge for a customer is $10. If the customer's monthly KW demand was 500 and his Power Factor was .70, the KVa would be 114. (see example) 90% of 714 equals 643, this becomes the "billing demand." To calculate the "demand cost" you multiply the billing demand by the demand charge (in this case $10) or 643 X $10 = $6,430.
A power factor of above .90
Now let's assume the same demand rate of $10 and KW demand 500. If the power factor was .90 the KVa demand would be 558 (see example). (90% of 556=500) This becomes the billing demand, and the demand cost is calculated the same way as above 500 X $10 = $5,000. So for the same 500 KW (working power) it would cost the customer $1,430.00 less at a power factor of .90 than at a .70 power factor.
With today's rapidly changing technologies and electrical environments, many "side effects" are created. Harmonics are one of the most potentially troublesome and unpredictable problems effecting the smooth operation of today's modern facilities.
Harmonics is a term used to describe distortion in an electrical distribution system and can be applied to both voltage and current. A typical building's electrical distribution system consists of a transformer (entry point of electricity from the utility) and distribution panels located throughout the building. Electricity travels between the transformer and the power panels via four main electrical wiring cables (three "hot phase" conductors and a return neutral conductor). From the power panels, individual circuits service the three-pronged wall outlets.
Conventional three-phase electrical distribution systems have been designed with the assumption that voltages and currents are pure sinusoidal waveform as shown in figure 1 (the 60 Hz waveform).
Figure 1
Non-sinusoidal (or distorted) waveforms can be broken down into several components. Each component, or harmonic, is a pure sine wave at a particular frequency. Figure 1 illustrates the fifth (300 Hz). In this example, the main distorted waveform consists of two components, the fundamental (60 Hz), harmonic and a fifth harmonic (5 x 60 = 300 Hz). The combined total of the fundamental (60 Hz) and the fifth, 300 Hz harmonic would look like figure 2.
Figure 2
Harmonic distortion is usually associated with an industrial, commercial and institutional facility's increased use of new energy saving and high tech devices. The most common three phase load none to create significant harmonics are, Adjustable Speed Drives for motors. Single phase loads are Solid State Lighting and any equipment using switching power supplies such as computers, fax, copy machines and most other modern office equipment. Just as experiencing high blood pressure can create serious stress and problems in the human body, high levels of harmonics can create stress and problems in manufacturing plants, office buildings, schools and hospitals. This can have a degradating and sometimes disastrous effect on electrical gear and loads.