What is Power Factor Correction VARS?

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SUMMARY

Power Factor Correction (PFC) involves understanding KVARs (Kilovolt-Amperes Reactive), which represent reactive power in electrical systems, particularly in relation to non-resistive devices like motors and solenoids. KVARs contribute to inefficiencies and increased costs, as they indicate excess current supplied by electricity retailers without performing productive work. The power triangle illustrates the relationship between watts, KVA, and KVAR, with a power factor (PF) calculated by dividing watts by KVA. For example, a motor rated at 10 kilowatts using 13 KVA results in a power factor of 0.77.

PREREQUISITES
  • Understanding of electrical power concepts, including watts, KVA, and KVAR.
  • Familiarity with three-phase electrical systems and calculations.
  • Knowledge of power factor and its significance in electrical efficiency.
  • Basic geometry to visualize and calculate values in the power triangle.
NEXT STEPS
  • Research methods for improving power factor in industrial settings.
  • Learn about the implications of KVARs on electricity billing and supplier charges.
  • Explore the use of capacitors for power factor correction.
  • Study the calculations involved in determining full load amps based on KVA.
USEFUL FOR

Electrical engineers, facility managers, and anyone involved in power quality management or optimizing electrical systems for efficiency.

johnnyb6231
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Hi Guys-

So, I'm new to the Power Quality world but have worked in the VFD world for some years.

The term "KVARS or VARS" is new to me.

Looking for a simple explanation and how they work in a system.

Thanks!
 
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KVARs are like watts in that they represent current through your meters and (usually) consequent billing by your electricity retailer. But unlike watts, KVARs do not perform work or do anything productive. KVARs are a consequence of non-resistive devices in your workshop, such as motors and solenoids. KVARs represent losses to you, and losses to the electricity supplier because he is supplying you with more current than you really need for the work your motors are performing. There are ways to reduce your KVARs, but none of these measures is inexpensive so efforts are almost never made to try to reduce KVARs right down to zero, through some measure of reducing them is encouraged by the supplier's punitive billing structure.
 
In regards to motors and most inductive loads...

Watts is the power that is measured at the shaft of the motor...in other words, how much power the motor makes at it's shaft is the watts or HP of the motor. KVA is the amount of electricity it takes to power that motor. KVAR is the amount of reactive power in the power triangle.

If a motor it rated at 10 Killowatts (about 13.5 HP) and uses 13 KVA of power...

To find the power factor...divide watts by VA...in this case 10/13 = .77 PF.

To find full load amps you need to base your amps on KVA...not watts.

Assuming 480 volts three phase...

13,000=480*1.73*I

Current will equal 15.65 full load amps per phase. Do not base full load amps on watts!

In regards to the power triangle...picture a triangle with one vector on the x axis...this is watts. Now picture another vector at 20 or 30 degrees or so from the same axis. Now connect the triangle at the end of those two vectors and the vertical line you just drew is reactive power. You can use simple geometry to figure exact numbers.
 

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