As a factory owner, or even the manager in charge of running the plant, you have probably heard a lot about Power Factor Correction. You have probably even had a company present a PFC solution to you in the past. But the concept of how such a system could have it's benefits may not be so clear. Understanding Power Factor Correction to it's core, may require further education in say Electrical Engineering and this may seem like too much work for the task at hand. As an owner, you want to ensure that the money you spend in installing one or multiple PFC systems will have a R.O.I. (And a good one at that). We recently read an article that helps non-engineers better understand what Power Factor Correction does and it's benefits. We thought we should share it with you.
Benefits:
Let us take a look at the benefits first:
- Reduced electrical bills.
- Increased electrical capacity in your plant/factory.
- Improved voltage.
- Harmonics Reduction (If your PFC system includes Harmonics Filters).
- Reduced losses through heat etc.
The Beer Analogy:
To understand the basics of Power Factor Correction turns out to not be that hard. But before I show you the Beer Analogy, let's take a look at some basic terms we will be using:
- Active Power (kW): The power that actually powers the equipment in your plant/factory and performs useful work. Something we want for sure. (Also known as Working Power, Actual Power or Real power).
- Reactive Power (kVAr): The power that magnetic equipment (i.e. Transformers, Motors, Relays etc.) requires in order to produce the magnetizing flux to run.
- Apparent Power (kVA): This is the "vectoral sumation" of your Active and Reactive Powers (i.e. The square root of the sum of the two squares of Active and Reactive Power respectively). This is what Eskom will charge you if you fit into the greater than 500kVA maximum demand per month tariff bracket
So to begin this analogy, say you and some friends are at your local pub on a hot Cape Town day. You order yourself a nice big mug of your favourite Craft beer. The part of your beer that will actually quench your thirst, is really only the kW part.
But, depending on how good your barman is at pouring your beer, your beer will always have some foam. And let's face it, foam just doesn't quench your thirst. It really only gets stuck to your beard. The foam here represents the Reactive Power or kVAr.
In this analogy, the total contents of your beer mug will thus be the summation of kW (The liquid beer) and the kVAr (The foam). Unfortunately, the barman will charge you for the mug size (Regardless of how much your liquid to foam ratio is).
So with this in mind, lets look at how this compares to Power Factor:
Power Factor (PF) = kW/kVA
Using the beer analogy, your PF would be the ratio of your liquid beer (kW) to your liquid beer plus foam (kVA).
PF = kW/(kW + kVAr) = Liquid Beer/(Liquid Beer + Foam)
Thus, for the given kVA (Or mug of beer):
- The more foam you have, the lower your Power Factor ratio will be.
- The less foam you have, the higher your Power Factor ratio will be. In fact, the closer your foam amount (kVAr) approaches zero, the more your PF gets closer to a ratio of 1.0
Please keep in mind, this Beer Analogy is a rather simplistic way of understanding and calculating your PF. Because to calculate kVA, you need to calculate the vectoral summation of your kW and kVAr.
This brings us to the Power Triangle:
With this we can see that, in an ideal situation:
- kVAr would be very small (Almost no foam).
- Your kW and kVA would be almost equal (More liquid beer than foam, get your money's worth).
Having a beer with more thirst-quenchiing liquid in it, would mean that you would need to order less beers to quench your thirst (Or get tipsy, depending on your goal here). The same applies in your plant. The more your kW's are equal to the amount of kVA's Eskom is charging you, the less kVA's you will require to do useful work.
Eskom's bill:
From our experience when it comes to large power users, Eskom looks at your Maximum Demand. This being, the maximum kVA demanded by your plant/factory in a 30min window for that billing period (Usually a month). With this value, they place your plant/factory into two seperate tariffs:
- Those where your Maximum Demand is 500kVA or higher.
- Those where your Maximum Demand is less than 500kVA.
In tariff 1, Eskom will bill you per kW you consume and then further to that, they will charge you for your Maximum Demand in that billing period. Your overall kW cost is relatively low (Around R0.6293 per kW), however you are charged around R187.27 per kVA for your maximum demand. To put that into perspective, if your Maximum Demand for a billing period is say 500 kVA, you will be charged R93 635.00 for that alone, besides your useful kW that you consume and are billed for. And this is if Eskom hasn't already increased these amounts.
In tariff 2, you are not billed for Maximum Demand, however you are billed for each kW you consume depending on the Time Of Use (TOU), this could be peak or off-peak charges. This usually does not even compare to what tariff 1 costs. So naturally, you would want to be part of this tariff.
A good Power Factor Correction system will bring your kVA down, helping you to either reduce your Maximum Demand cost or also maybe help you to go into tariff 2 if your Maximum Demand can be brought down below 500kVA.
Keep in mind however, Power Factor Correction should be one of the first steps you need to take in order to save costs and make your plant more efficient. But it doesn't stop there. Doing proper load sharing (Which helps to reduce Maximum Demand even more) and load shedding (Which helps a lot if you are in tariff 2, to help avoid peak costs), can help further your savings and efficieny.
Please remember though, in order to get ensure that you get the correct Power Factor Correction system, you need a professional in-depth energy audit done at your plant/factory. Here at Futre (Pty) Ltd, our engineers provide you that very service along with full Power Factor Correction and Energy Management/Monitoring systems.
Contact one of our sales persons at This email address is being protected from spambots. You need JavaScript enabled to view it. for more information.
Article References:
Electrical Engineering Portal: http://electrical-engineering-portal.com/beer-mug-and-power-factor