Tag Archives: Power Factor

Dr InPhase Edu Series – An Exercise in Reactive Power Calculation

Doctor_Character-04-1Good day every body, Today on our Edu Series we will focus on some practical knowledge related to Reactive Power calculation.  Calculating your reactive power is critical as it can help make sure that your design is reliable and you get a reliable power factor output.

Consider an electrical network with the details below,

Demand = 2500kVA; Initial PF1 = 0.76; Desired PF2=0.97.

The reactive power required to achieve the desired PF (0.97), is calculated as below:

We know that

Where φ is the angle between voltage and current vectors.

From the above,

Now here arises the doubt. We say, the above method of calculation is flawed. There is a fundamental electrical engineering mistake. Before you go on any further, we would like you to think and comment in the comments section below if you find the flaw. Because once you scroll down, you are likely to lose your unique perspective on the above. Therefore, please comment and proceed for the answer below. This can help knowledge sharing with numerous angles / perceptions. Thanks in advance for that.


The mistake is in Point ②. We have considered the same kVA for ① where the pf is 0.76, and② where the pf is 0.97. When actually, it is Real Power or kW which remains constant. Load remains unchanged, which in other words translates into constant kW and NOT constant kVA.  The same is shown in the diagram below:

From the above diagram, we know now the ‘kvar’ required to improve the system from PF1 to PF2 (i.e, 0.76 to 0.97) is,

Applying Pythagoras theorem for the above diagram,


Which implies, [kvar1 = kW × tan φ1] and [kvar2 = kW × tan φ2]. Substituting these in equation ④,

In terms of power factors,

This is a generic formula to calculate the reactive power demand when the present power factor and the desired power factor are known. The same formula reduces to the following for desired power factor being Unity.

Where φ is the power factor angle.

We sincerely hope that this exercise helps you in calculating reactive power demand with more clarity.

Do you have a Challenging Power Factor Correction or Compensation issue, no matter how dynamic your load or reactive power is we can find the right solution for you. Get in touch with us today.

This article was originally published in www.pqindia.in.

The author Mr. Hasan Mydin is part of the “Advanced Power Quality Solutions” department at InPhase. He is a self-confessed Power Quality enthusiast with more than a decade’s experience solving power quality problems across India and even abroad. To know more about him, check out  his LinkedIn Profile.

Meet you again with a interesting article, until then  bye from Dr.InPhase

Thank you!


Thanks for reading…if you have questions don’t forget to ask me. You could write to me to info@inphase.in or call +919632421402


IEEMA the industrial association for Electrical Industries is very proactive in educating and creating awareness in the market. Today IEEMA has announced a very insightful workshop on  Power Quality and Reactive Power Compensation. Take a look at the agenda and get in touch today to be part of this excellent program. We will meet you there.


Reactive Power Management has become very important now-a-days because of introduction of power factor based tariff. Power Factor (PF) is crucial in all Electrical Power utilizing environments. A good understanding of Power Factor is essential for practicing Electrical Engineers and middle level managers as a good control of PF could lead to many advantages – energy saving, reduction of current loading, higher output from motor and generators, longer life for cables and equipment  – to mention a few. However, the equipment that is used to improve power factor interacts with network harmonics and brings down overall reliability. This workshop addresses such issues and gives solution to mitigate these problems.





14th October 2016, Friday

10:00 am to 5:00 pm

The Fern Citadel Hotel
No. 41, Seshadri Road,
Ananda Rao Circle, Bangalore – 560 009
Tel : +91 080 4240 2222

Key Benefits

  • Gives basic knowledge of fundamentals of Reactive Power Management
  • Can be applied directly to any installation and hence a boon for Engineers and others
  • Gives knowledge about Power Quality in general and Harmonic pollution in particular along with practical solution to mitigate them


  • Benefits of Power Factor Improvement
  • Evaluating PF from Electricity Bill
  • Methods of improving Power Factor
  • Automatic Power Factor Correction (APFC)
  • Issues in Power Quality
  • Power Factor Improvement of DG Sets
  • Harmonics – Causes, Measurement and Mitigation
  • Harmonics and effect of adding Capacitors in the System
  • Harmonic Filters and Active Compensation

Target Audience

Transmission and Distribution Operating Personnel, Engineers involved in Planning, Designing and Testing of Power Control Equipment and Engineers in charge of Electrical Maintenance, Engineers from Public / Private Sector Power Utilities.

However, anyone with enthusiasm and interest for Power Systems are most welcome to attend.



k-subramanianA  Masters Degree in Electrical Engineering and having an overall experience exceeding over 30 years in various fields such as Design, R&D, Production, Erection & Commissioning. Presently working as a freelancer in Bangalore. His current activities include promoting Electrical Power Quality awareness in the fields of Harmonics and Reactive Power Management. A regular faculty in PSTI (Min of Power), Bangalore, Larsen & Toubro Switchgear Training Centres, and conducted program on DRUM (Distribution Reforms, Upgradation and Modernization) organized by (Min of Power) Govt. of India and aided by Govt. of USA. Visiting faculty in various Engineering Colleges.

WorkShop Fees:
Members : 3000
Non Members: 3500

For Registration Contact:  k.seetharaman@ieema.org
Mobile : +91 99800 04982 (Seetharaman K)

Visit www.ieema.org for more details!


Team InPhase will be hoping to meet you there! Cheers!