Understanding power factor is not that hard. We have some very common example from the real life you will understand for sure, but first let’s start with some introduction of power factor.
To understand power factor, we’ll first start with the definition of some basic terms:
kW is Working Power (also called Actual Power or Active Power or Real Power). It is the power that actually powers the equipment and performs useful work.
kVAR is Reactive Power. It is the power that magnetic equipment (transformer, motor, relay etc.) needs to produce the magnetizing flux.
kVA is Apparent Power. It is the “vectorial summation” of KVAR and KW.
Example From the Real Life ;)
Let’s look at a simple analogy in order to better understand these terms….
Let’s say you are at the park and it is a really hot day. You order up a mug of your favorite Cola.
1. The thirst-quenching portion of your cola is represented by KW. Unfortunately, life isn’t perfect.
2. Along with your ale comes a little bit of foam. (And let’s face it…that foam just doesn’t quench your thirst.) This foam is represented by KVAR.
3. The total contents of your mug, KVA, is this summation of KW (the cola) and KVAR (the foam).
P.F. = KW /(KW + KVAR)
= Cola/(Cola+ Foam)
What Causes Low Power Factor?
Since power factor is defined as the ratio of KW to KVA, we see that low power factor results when KW is small in relation to KVA. Remembering our Cola mug analogy, this would occur when KVAR (foam) is large.
What causes a large KVAR in a system?
The answer is…inductive loads.
Inductive loads (which are sources of Reactive Power) include:
Transformers
Induction motors
Induction generators
High intensity discharge (HID) lighting
These inductive loads constitute a major portion of the power consumed in industrial complexes.
Why Should I Improve My Power Factor?
1) Lower utility fees by:
a. Reducing peak KW billing demand Recall that inductive loads, which require reactive power, caused your low power factor. This increase in required reactive power (KVAR) causes an increase in required apparent power (KVA), which is what the utility is supplying. So, a facility’s low power factor causes the utility to have to increase its generation and transmission capacity in order to handle this extra demand. By raising your power factor, you use less KVAR. This results in less KW, which equates to a dollar savings from the utility.
b. Eliminating the power factor penalty Utilities usually charge customers an additional fee when their power factor is less than 0.95. (In fact, some utilities are not obligated to deliver electricity to their customer at any time the customer’s power factor falls below 0.85.) Thus, you can avoid this additional fee by increasing your power factor.
2) Increased system capacity and reduced system losses in your electrical system
By adding capacitors (KVAR generators) to the system, the power factor is improved and the KW capacity of the system is increased.
For example, a 1,000 KVA transformer with an 80% power factor provides 800 KW (600 KVAR) of power to the main bus.
By increasing the power factor to 90%, more KW can be supplied for the same amount of KVA.
The KW capacity of the system increases to 900 KW and the utility supplies only 436 KVAR. Uncorrected power factor causes power system losses in your distribution system.
By improving your power factor, these losses can be reduced. With the current rise in the cost of energy, increased facility efficiency is very desirable. And with lower system losses, you are also able to add additional load to your system.
How Do I Correct (Improve) My Power Factor?
We have seen that sources of Reactive Power (inductive loads) decrease power factor:
Inductive loads (which are sources of Reactive Power) include:
Transformers
Induction motors
Induction generators
High intensity discharge (HID) lighting
Similarly, consumers of Reactive Power increase power factor:
Capacitors
Synchronous generators (utility and emergency)
Synchronous motors
NATURAL POWER FACTORS FOR THREE PHASE ELECTRICAL INSTALLATIONS
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