POWER FACTOR EXPLAINED
It has come to my attention that there is still some confusion as to what we mean by Power Factor. Along the way there are many parts to what we say when we are talking about the subject. Several terms are used: Cosine Theta, Reactive Power versus Real Power, Slope Difference, Sine Wave Divergence, Current Delay and even some others. Like the old adage that “A rose by any other name is still a rose” fits here. The names mean nothing. So let us put it all into a simple term that is the real definition anyway and understandable to anyone.
From now on let us define Power Factor as efficiency. Because that is what it is. Whenever Power Factor is shown it is always in the form of a decimal number. The typical Power Factor in most factories is around .75. But we see all kinds of other numbers such as .64, .79, .82, and even .98 or some other decimal number. Simply put, what that number means is the declaration of efficiency. If the PF is .75 then we are saying that this building is electrically 75% efficient. But here is the part that is not remembered. It is that if you are 75% efficient, then you are 25% inefficient. Straight to the point, this electrical customer is paying for electricity that he never got to use, and that total is 25% or 1/4th of his whole bill. THAT is a lot for anyone to put their mind around. However, believable or not, this is power paid for and then wasted in a typical building.
And the simple solution or answer to that is this: Eliminate the waste, and you only pay for what you use and not what you are wasting. Not clear yet? Look at it this way. If you eliminate that 25% waste, then you are not paying for the power you never had available. That 25% which you eliminated comes back to you in the form of a 25% reduction in your bill. Fair enough? Reduce waste and eliminate paying for waste. You have not used more electricity to do your work. You are just using all of what you buy. The 25% that used to be wasted is no longer on your bill.
The power factor declaration is determined by how far the arriving Current sine wave is behind, or in front, of the Voltage sine wave. It is all about time. Enough Inductive reactance will cause passing current to be very slightly delayed. That delay changes the ability of power to be used. If you were to look at a picture of voltage and current together at a plant with a PF of .75 you would see that the Voltage sine wave is in front of the Current sine wave. That is where the inefficiency mostly comes from. It is because the two sine waves are not together.
Why does that matter? Well we arrive at Watts or power itself with the formula of P=VxA or Power is equal to Volts times Amps. (commonly called current) Voltage is defined in electricity as the pressure behind the electrons. Current, defined in Amps is the amount of electrons themselves that are passing by to create work. That work can be in light, motor torque or even heat. All of it is what we do with electricity. But in a previous paragraph we told you that PF is when the Voltage and the Current are not together. If they are only together 75% of the time, you cannot get the Watts you want if what you multiply together are only together part of the time. That should be plain enough.
So where did the waste come from? It is in that part where the Volts and the Amps or Current are not together. Remember that the meter which determines the bill only reads the Current, not the Voltage. The meter does not care if the Current and Voltage are not together. You are going to be billed when the Current goes by. It has no way of knowing or caring that you cannot use all of the Current that is passing through with no Voltage to make it work. Here I need to make a correction. I said that the utility company didn’t care if you are inefficient. Actually they do. It is just not their fault. They can only bill you for the Current they read. But the utility company knows what is going on. When they see the sine waves slightly apart, they know what the PF is and put it on your bill. So that is where the PF of .75 on the bill comes from.
Some utility companies will charge you a penalty for that inefficiency because although the waste comes from the customer, some of it does reflect back into the power line. And some utility companies don’t charge you a penalty but if it is there anyway. Now pay attention to this. Here is the shock. Power use customers hate the penalty if they get one. But what is not understood is that the penalty is only 10% or 20% of the real loss in power. That 20% is only the utility company’s part. The customer endures the other 80%. So if you have a common $500 penalty from the power company, then you are most likely wasting $2,500 worth of electricity yourself. That makes the total loss to the customer now $3,000 of power they never used.
Customers are always amazed that we often accurately predict what their power bills are with some basic information. When a client tells me they are paying a $500 penalty, I can often say they probably have a $10,000 monthly power bill. How on earth did you know that they ask? Well, I assume that if they are a typical manufacturer and have enough motors and transformers then they most likely will average a Power Factor of .75. I naturally now assume that they are wasting 25% of their electrical power. Since the penalty is only 20% of the total waste, then I guess that they are really wasting $2,500 a month. If that amount is equal to a waste of 25% of the whole bill then I know that the rest of the bill will be four times as much or $10,000. Simple actually.
So what is the answer? Simple again. Eliminate waste. Eliminate what was 25% and the bill has to go down that much. Right? It does not take an electrical engineer to understand that . Unfortunately, in nature nothing is every perfect. Eliminating all of the waste just does not happen entirely because of dozens of reasons. But you can eliminate most of it. A PF of .98 is very attainable. So, you may not be able to get all that $2,500 of your bill but I bet you can get $2,200 of it back. Would that be good? I hope so.
So where were we? Power Factor or efficiency. Simple answer, simple solution. Undo what causes the two sine waves to be apart and you now can use all or nearly all of what you are paying for. Change PF from .75 to .95 and you ought to see at least a 20% reduction in your bill because you are not now paying for wasted power any more.
Before we sign off there is some confusion as to what Power Factor is not. The greatest part of the electrical world does not understand Power Factor anymore. I say anymore because your grand fathers did. It has been forgotten because other things changed what used to work years ago. Something has been destroying what was used years ago to decrease Power Factor Error. That something is called Harmonic Distortion. We will not deal with that in this paper but we do need to clear up again what Power Factor is not.
Looking at a power bill the words DEMAND show up. And behind that word is usually another penalty. I say another because that is what it is. Power Factor is one penalty and Demand is another one. But the two are not the same. Most customers don’t pay attention to the PF penalty if it is even on their bill and for many it is not. What they do see is that demand bill and it is usually enough to get anyone’s attention. Demand penalty is the whole thing. Power Factor penalties are only a small part of what is lost. Demand is not a loss the way that Power Factor is.
So what is demand? Electricity is on the power line whether we use it or not. And the utility produces just enough to meet what is called for. That production goes up and down as customers on the line use it. So the utility company watches what is being used carefully and try to keep use and production equal. But some manufacturers will on occasion use more for a short time than they use most of the time. Usually it is at start up in the morning when they all get to work. Their plant has been running idle all night long and the utility company has produced accordingly. Now all of a sudden they turn all their motors on. Motors run on less electricity when they are still running than they do when they first start up. When a motor starts is uses about 130% more electricity to get up to speed than it does when it is already running. So in the morning they will demand extra electricity beyond what they will use all the rest of the day.
This extra demand will cause the utility company to rev up their generators to keep up with the extra demand. There is that word again. And when they have to do it, the price per kilowatt is more. So they install meters at the factory to see when that factory exceeds their normal draw. Not only does demand occur in the morning, if that company adds another line or does something that calls for extra power, then they have a second or even third demand call. The utility company keeps track of how long and how many of those extra demands this customer calls for and they add it to the bill. For many electrical user companies, the Demand bill can be half of the total. No wonder it gets their attention.
And there are ways to drastically reduce demand but we will not deal with that in this paper.
This paper is about Power Factor. And Power Factor has nothing at all to do with Demand. They are completely different issues. But learn one thing. If something can be detected it can be reduced or eliminated. My advice to anyone is to deal with anything that costs you money. Deal with enough of them and combined, one may save a great deal of money when all added up.
In conclusion, since grandpa left without talking about Power Factor very much, we have forgotten about it. And along the way the story tellers have guessed as to what Power Factor is and is not. But they didn’t tell anyone that they were guessing. The story sounded good so it stuck. Here are the facts. Power Factor can be almost entirely eliminated. Yes it can. And I want you to note that I used the word almost. Because we can’t get all of it yet, but we are close. And close is much better than none. Even a little is better than nothing which is our condition for many years. No wonder there is so much confusion as to what it is all about.
Any more questions I am available to anyone. And if you don’t want to talk to me, there are others who will tell you the same thing, including new electricians fresh out of class who are being taught about Power Factor because it is a major problem in the electrical world.
John Jackman, Electrical Engineer 801-272-1948 and cell at 801-703-7175 or fax at 801-272-2152
* There is no copyright for this paper. It is public information provided it is not reworded or altered in any way. It is to be used in explaining electrical principles. Use it to benefit anyone who might need the information. You are restricted only in that you are forbidden to make any changes of any kind. I will take no responsibility for what I did not write.
It has come to my attention that there is still some confusion as to what we mean by Power Factor. Along the way there are many parts to what we say when we are talking about the subject. Several terms are used: Cosine Theta, Reactive Power versus Real Power, Slope Difference, Sine Wave Divergence, Current Delay and even some others. Like the old adage that “A rose by any other name is still a rose” fits here. The names mean nothing. So let us put it all into a simple term that is the real definition anyway and understandable to anyone.
From now on let us define Power Factor as efficiency. Because that is what it is. Whenever Power Factor is shown it is always in the form of a decimal number. The typical Power Factor in most factories is around .75. But we see all kinds of other numbers such as .64, .79, .82, and even .98 or some other decimal number. Simply put, what that number means is the declaration of efficiency. If the PF is .75 then we are saying that this building is electrically 75% efficient. But here is the part that is not remembered. It is that if you are 75% efficient, then you are 25% inefficient. Straight to the point, this electrical customer is paying for electricity that he never got to use, and that total is 25% or 1/4th of his whole bill. THAT is a lot for anyone to put their mind around. However, believable or not, this is power paid for and then wasted in a typical building.
And the simple solution or answer to that is this: Eliminate the waste, and you only pay for what you use and not what you are wasting. Not clear yet? Look at it this way. If you eliminate that 25% waste, then you are not paying for the power you never had available. That 25% which you eliminated comes back to you in the form of a 25% reduction in your bill. Fair enough? Reduce waste and eliminate paying for waste. You have not used more electricity to do your work. You are just using all of what you buy. The 25% that used to be wasted is no longer on your bill.
The power factor declaration is determined by how far the arriving Current sine wave is behind, or in front, of the Voltage sine wave. It is all about time. Enough Inductive reactance will cause passing current to be very slightly delayed. That delay changes the ability of power to be used. If you were to look at a picture of voltage and current together at a plant with a PF of .75 you would see that the Voltage sine wave is in front of the Current sine wave. That is where the inefficiency mostly comes from. It is because the two sine waves are not together.
Why does that matter? Well we arrive at Watts or power itself with the formula of P=VxA or Power is equal to Volts times Amps. (commonly called current) Voltage is defined in electricity as the pressure behind the electrons. Current, defined in Amps is the amount of electrons themselves that are passing by to create work. That work can be in light, motor torque or even heat. All of it is what we do with electricity. But in a previous paragraph we told you that PF is when the Voltage and the Current are not together. If they are only together 75% of the time, you cannot get the Watts you want if what you multiply together are only together part of the time. That should be plain enough.
So where did the waste come from? It is in that part where the Volts and the Amps or Current are not together. Remember that the meter which determines the bill only reads the Current, not the Voltage. The meter does not care if the Current and Voltage are not together. You are going to be billed when the Current goes by. It has no way of knowing or caring that you cannot use all of the Current that is passing through with no Voltage to make it work. Here I need to make a correction. I said that the utility company didn’t care if you are inefficient. Actually they do. It is just not their fault. They can only bill you for the Current they read. But the utility company knows what is going on. When they see the sine waves slightly apart, they know what the PF is and put it on your bill. So that is where the PF of .75 on the bill comes from.
Some utility companies will charge you a penalty for that inefficiency because although the waste comes from the customer, some of it does reflect back into the power line. And some utility companies don’t charge you a penalty but if it is there anyway. Now pay attention to this. Here is the shock. Power use customers hate the penalty if they get one. But what is not understood is that the penalty is only 10% or 20% of the real loss in power. That 20% is only the utility company’s part. The customer endures the other 80%. So if you have a common $500 penalty from the power company, then you are most likely wasting $2,500 worth of electricity yourself. That makes the total loss to the customer now $3,000 of power they never used.
Customers are always amazed that we often accurately predict what their power bills are with some basic information. When a client tells me they are paying a $500 penalty, I can often say they probably have a $10,000 monthly power bill. How on earth did you know that they ask? Well, I assume that if they are a typical manufacturer and have enough motors and transformers then they most likely will average a Power Factor of .75. I naturally now assume that they are wasting 25% of their electrical power. Since the penalty is only 20% of the total waste, then I guess that they are really wasting $2,500 a month. If that amount is equal to a waste of 25% of the whole bill then I know that the rest of the bill will be four times as much or $10,000. Simple actually.
So what is the answer? Simple again. Eliminate waste. Eliminate what was 25% and the bill has to go down that much. Right? It does not take an electrical engineer to understand that . Unfortunately, in nature nothing is every perfect. Eliminating all of the waste just does not happen entirely because of dozens of reasons. But you can eliminate most of it. A PF of .98 is very attainable. So, you may not be able to get all that $2,500 of your bill but I bet you can get $2,200 of it back. Would that be good? I hope so.
So where were we? Power Factor or efficiency. Simple answer, simple solution. Undo what causes the two sine waves to be apart and you now can use all or nearly all of what you are paying for. Change PF from .75 to .95 and you ought to see at least a 20% reduction in your bill because you are not now paying for wasted power any more.
Before we sign off there is some confusion as to what Power Factor is not. The greatest part of the electrical world does not understand Power Factor anymore. I say anymore because your grand fathers did. It has been forgotten because other things changed what used to work years ago. Something has been destroying what was used years ago to decrease Power Factor Error. That something is called Harmonic Distortion. We will not deal with that in this paper but we do need to clear up again what Power Factor is not.
Looking at a power bill the words DEMAND show up. And behind that word is usually another penalty. I say another because that is what it is. Power Factor is one penalty and Demand is another one. But the two are not the same. Most customers don’t pay attention to the PF penalty if it is even on their bill and for many it is not. What they do see is that demand bill and it is usually enough to get anyone’s attention. Demand penalty is the whole thing. Power Factor penalties are only a small part of what is lost. Demand is not a loss the way that Power Factor is.
So what is demand? Electricity is on the power line whether we use it or not. And the utility produces just enough to meet what is called for. That production goes up and down as customers on the line use it. So the utility company watches what is being used carefully and try to keep use and production equal. But some manufacturers will on occasion use more for a short time than they use most of the time. Usually it is at start up in the morning when they all get to work. Their plant has been running idle all night long and the utility company has produced accordingly. Now all of a sudden they turn all their motors on. Motors run on less electricity when they are still running than they do when they first start up. When a motor starts is uses about 130% more electricity to get up to speed than it does when it is already running. So in the morning they will demand extra electricity beyond what they will use all the rest of the day.
This extra demand will cause the utility company to rev up their generators to keep up with the extra demand. There is that word again. And when they have to do it, the price per kilowatt is more. So they install meters at the factory to see when that factory exceeds their normal draw. Not only does demand occur in the morning, if that company adds another line or does something that calls for extra power, then they have a second or even third demand call. The utility company keeps track of how long and how many of those extra demands this customer calls for and they add it to the bill. For many electrical user companies, the Demand bill can be half of the total. No wonder it gets their attention.
And there are ways to drastically reduce demand but we will not deal with that in this paper.
This paper is about Power Factor. And Power Factor has nothing at all to do with Demand. They are completely different issues. But learn one thing. If something can be detected it can be reduced or eliminated. My advice to anyone is to deal with anything that costs you money. Deal with enough of them and combined, one may save a great deal of money when all added up.
In conclusion, since grandpa left without talking about Power Factor very much, we have forgotten about it. And along the way the story tellers have guessed as to what Power Factor is and is not. But they didn’t tell anyone that they were guessing. The story sounded good so it stuck. Here are the facts. Power Factor can be almost entirely eliminated. Yes it can. And I want you to note that I used the word almost. Because we can’t get all of it yet, but we are close. And close is much better than none. Even a little is better than nothing which is our condition for many years. No wonder there is so much confusion as to what it is all about.
Any more questions I am available to anyone. And if you don’t want to talk to me, there are others who will tell you the same thing, including new electricians fresh out of class who are being taught about Power Factor because it is a major problem in the electrical world.
John Jackman, Electrical Engineer 801-272-1948 and cell at 801-703-7175 or fax at 801-272-2152
* There is no copyright for this paper. It is public information provided it is not reworded or altered in any way. It is to be used in explaining electrical principles. Use it to benefit anyone who might need the information. You are restricted only in that you are forbidden to make any changes of any kind. I will take no responsibility for what I did not write.