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Power Factor Correction - Huh? By John Cavallaro Carolina Power & Light Raise your hands, if you know why power factor is important to you? Maybe, before you raise your hands you might want to know what power factor is? Well . . . mathematically, it is the relationship of real power divided by complex power, or PF = P / S. So What?? This doesn’t mean anything to the MIS manager who has been told that he has poor power factor on his critical load bus. He wants to know what it is doing to his critical power and how can he get rid of it. Get rid of it! On the contrary, you want to have as much power factor as you can. For the layman, power factor is a numerical representation that tells the customer how efficiently he is using his power. It tells him how much power he is paying for, but throwing away. Power factor numbers range from 0.0 to 1.00, with 1.00 meaning that all of the power is used by the customer or the critical load. Maintaining a high power factor in a plant can yield direct savings. Some, such as reduced power bills and release of system capacity, are obvious examples. Others, such as improved voltage and decreased heating losses, are less obvious but real. For example, lets pick a power factor, or PF, say: 0.70. This means that that location is only using 70% of his power to perform useful work. The other 30% is carried by the facility wiring and power distribution system as magnetizing effects, effectively reducing the load carrying capability of the wiring. But . the customer must pay for this 30%. Why? Because Utilities still have to supply that 30% to the customer. If you check with the Utility, you will probably find out that their charges are based on delivering a specific power factor, or KVA load. If they notice that a particular customer is running at a lower power factor, they will charge an extra premium for that extra power that the customer is throwing away. So how does one fix this? Adding Capacitors generally is the most economical way to improve the plant power factor, especially in existing plants. But at the critical load level, such as; motors, manufacturing equipment, the best way to protect against low power factor is to NOT install equipment that runs at a low power factor. This is not that hard to do. Almost all high technology equipment purchased to day will specify the power factor that it exhibits. Therefore, one can easily maintain a high power factor level on all new equipment purchased. As older low PF equipment is discontinued, the total facility PF will go up, reducing electric charges, and increasing capacity.
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