presentation for power factor

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raiderUM

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I am doing an independent study in my final semester at school and I am giving a presentation in class on power factor and how we correct it on campus. The issue is that I seem to lose everyone and I get a lot of blank looks. I need the presentation to be very simple and basic, but I do not know how to give a presentation on just the beer analogy!!

Any thoughts on how I can get construction management students to understand these concepts without losing them??? Have any of you had to do something similar?

Thanks!
 
I have used this for PF Presentations many times and it works (forget about vector analysis at the start etc.)

You and your buddy are one side of a fast flowing 100 foot wide river.:):D

Directly across this river are 2 very beautiful guys/girls (depending on the group's ac/dc slant)
sunbathing.:cool::cool:

Your buddy hops in the first canoe and frantically paddles to the other shore.He eventually makes it across but is 1 mile downstream.By the time he runs back up the shore to these guys/girls he is tired / sweating and totally exhausted.:weeping:


Before entering your canoe, you slap on a backpack of powerfactor capacitors and have a very easy paddle directly across the river to this group on the other shore.You are not exhausted and ready to party all night long with them.:roll:

Once they understand this efficiency example, you can gradually start adding the vectors as travelling point vectors.

Good Luck:p
 
130328-1604 EDT

First, define Power factor (PF).

PF = Power/Volt*Amperes

where
Power is "real power" to the load. The measurement of the rate of doing work.
Volt*Amperes is the RMS voltage across the load times the RMS current thru the load.

Somehow get them to understand what power and energy are and their relationship to each other.

For the most part power or energy is what you buy from the power company and that is measured by a watt or watt-hour meter. You do not buy volts or amperes or volt-amperes from the power company.



Second, Volts times Amperes is not power but is Volt-Amperes. This is a different measurement and its numeric value may or may not equal power. With some kind of additional information, for example Power-Factor, it may be possible to relate a VA measurement with a power measurement.

Under limit conditions, basically a resistive load, the VA value will equal the power level. Under any other conditions the VA value will be greater than the power value.

In a distribution system there is resistance in the wiring. Here the wasted power loss, does no output useful work, is determined by a constant times the RMS current squared in the distribution wiring. For maximum efficiency from the input power source to the output load you want to minimize the losses. Thus, as seen by the distribution system you want the power factor to be 1.0 or close to it so there is a minimum current to do the end job.


If you can provide a means to correct bad Power Factor at the load end, then you can improve the distribution system efficiency. Not all types of bad power factor can be corrected.


.
 
Real energy is consumed across both halves of a cycle. Reactive energy is stored temporarily on one half of the cycle but returned on the other half.

Power measures the rate of energy exchange.

Apparent power "VA" is the combination of both real power "P" (watts), and reactive power "Q" (measured in vars). While we assigned them different unit designations, VA, P, and Q all have the same fundamental units because they are all power.

Apparent power is a factor in equipment sizing because the equipment has to handle both the exchange of consumed energy and temporary energy.

Even though reactive energy is temporarily stored and later returned, there are real energy losses associated with the storage and transport of the reactive energy.

Power factor is a measure of the relative size of real and apparent power and is the ratio of real to apparent power.
 
raiderUM,

You mentioned correcting the power factor so my post addressed "VA" being the combination of real power "P" and reactive power "Q". I'm not sure how much more light you want to shine in the deer-eyes but there is also a distortion component of VA due to harmonics.

Without distortion, we have VA2 = P2 + Q2. Here we are confined to a two-dimensional X-Y plane with real components plotted on a paper's horizontal X-axis and reactive components plotted on a paper's vertical Y-axis. Power factor correction here (like with capacitors) changes the vertical "Q" component.

With harmonic distortion, we have VA2 = P2 + Q2 + D2. Here we are in 3-D space with real components plotted on a paper's horizontal X-axis, reactive components plotted on a paper's vertical Y-axis, and distortion components located above the paper plane on the perpendicular Z-axis. Power factor correction with capacitors still changes the vertical "Q" component on the paper's Y-axis, but correction of the "D" component requires filters and changes the values on the Z-axis (elevation above the plane of the paper).

You can visualize all this with a flat surface and pencil. Holding the eraser stationary and swinging the point up along the face of the surface (like a moving clock-hand) shows the "P" & "Q" components of the pencil length "VA". Elevating the point above the paper illustrates the "D" component coming into play (like bending the clock hand away from the clock face).

The end result is that normal power factor correction techniques like capacitors to correct the "Q" component may not be able to mitigate the power factor to unity because you will still be left with the "D" component along the Z-axis (the clock hand would still be bent).
 
They have to understand what reactive load is before they can grasp PF. I used to use a superball to teach this concept but it is hard to explain on a blog (Tried before here and failed)
 
You got me thinking. I have always had a hard time getting my head around the concept that voltage and current can be out of phase with each other, so I just accept it. Perhaps that is the first thing you should tell them. Then what do the others here think about this. One Superhero (Greenie) gets his power from the color green. Just blue power, or just Yellow power does absolutely nothing for him. So, (hold up blue and yellow celophane) as blue and yellow power start to overlap he gets stronger. Not until they are perfectly aligned does he reach maximum power. Our other Superhero Volt-Holt (get it Mike?) gets his power from voltage and amps etc. Anyone think that analogy would work?

I would have gone with sound and the beats for tuning, but only some people like Dennis Alwon would pick up on it!
 
Thank you all for the responses! I appreciate it! I know what you are all saying, maybe it is just me and my inability to explain how power factor or capacitors work. Even my department chair who is a PE was lost when I started to explain it to him, but he is just a highway/concrete guy. Keeping it very simple in order for sophomores knowing nothing about electricity, and grasping this concept is going to be a difficult task. Any other suggestions? Keep them coming...
 
raiderUM said:
Thank you all for the responses! I appreciate it! I know what you are all saying, maybe it is just me and my inability to explain how power factor or capacitors work. Even my department chair who is a PE was lost when I started to explain it to him, but he is just a highway/concrete guy. Keeping it very simple in order for sophomores knowing nothing about electricity, and grasping this concept is going to be a difficult task. Any other suggestions? Keep them coming...
Click to expand...
If they understand energy, something similar to my post #4 should be fine.

If we want to go more elementary, then a parallel to Zog's superball that is so-so is the basketball analogy. Real energy is what we use to move the basketball in either direction up and down the court.

A requirement is that we must keep the ball in motion by bouncing it. Reactive energy is the back-and-forth exchange in potential energy and kinetic energy as the ball bounces. Reactive loss is the little bit of extra push we have to add because the ball does not bounce all the way up because the bounce height decays. Passing the ball eliminates the need for the bouncing energy (assumes no potential energy loss so no passing from Shaq to Spud Web).
 
raiderUM said:
Any thoughts on how I can get construction management students to understand these concepts without losing them???
Click to expand...
A sticky wicket. A difficult pitch.

I imagine construction management students do not have a background in electrical theory.
On that basis, you might be better explaining what it does rather than attempting to explain how or why it does what it does. Which they probably won't get anyway.
Steer away from the concepts. Forget vectors. Go for the practicalities.

So, how to present that?
Well, power factor correction reduces supply current. That's a good thing because?
Most electrical systems are rated for current. Lower currents mean you can install smaller transformers, switchgear, cables with attendant capital cost savings, particularly at the construction phase.

Then there is the issue that some utilities impose financial penalties for poor power factor (for much the same reasons). Power factor correction can mitigate/avoid such penalties. Again, it's about cost savings.

Don't know if this helps or hinders.
I've done a fair bit of training at grass roots level and presented papers to international conferences.
The best bit of advice I got was know your audience and pitch to that.
 
Besoeker said:
A sticky wicket. A difficult pitch.

I imagine construction management students do not have a background in electrical theory.
On that basis, you might be better explaining what it does rather than attempting to explain how or why it does what it does. Which they probably won't get anyway.
Steer away from the concepts. Forget vectors. Go for the practicalities.

So, how to present that?
Well, power factor correction reduces supply current. That's a good thing because?
Most electrical systems are rated for current. Lower currents mean you can install smaller transformers, switchgear, cables with attendant capital cost savings, particularly at the construction phase.

Then there is the issue that some utilities impose financial penalties for poor power factor (for much the same reasons). Power factor correction can mitigate/avoid such penalties. Again, it's about cost savings.

Don't know if this helps or hinders.
I've done a fair bit of training at grass roots level and presented papers to international conferences.
The best bit of advice I got was know your audience and pitch to that.
Click to expand...

I think you hit the nail on the head.... I have struggled all weekend with different ideas and how to get the students to understand or take something away from my presentation. I believe I am going to just stick with basics. Show them some pictures of transformers, main distribution, and cap banks that we currently have at one of our academic buildings. I'll also go over some very basic electrical concepts like voltage, current, and use simple analogies to help them understand. After I go over these I'm sure half the class will be lost, so I might as well start in on cap banks and lose the other half. :blink:

I really think you are correct in saying I need to know my audience.... I want the students going into construction industry to take something away from this presentation, to at least know what a transformer looks like and an MCC. At least this way they can apply this in their future careers and know something about electric.
 
I like to introduce the concept this way. Most of us know that if you wrap a wire around a nail and attach a battery to the wire, you will have an electromagnet. You can use this ?tool? to pick up paper clips, for example. However, even before you try to pick up your first paper clip, there is current flowing through the wire, and there is a magnetic field that is not doing anything. You have to expend some amount of energy just to create the magnetic field.

When you start picking up paper clips, there will be more current flowing in the wire. The magnetic field is now doing some useful work. The total current in the wire can be treated as being two separate currents flowing at the same time. One current establishes the magnetic field. That one is almost a waste of energy (and money), in that you don?t get any work out of it. But you would not be able to do any work if it were not there. So it is something of a necessary evil. The second current is what is allowing the magnet to do its work.

The physical phenomena taking place in an AC circuit that has a power factor lower than 1.0 is analogous, to at least a small degree. Let?s consider a motor that has a power factor of 0.8. Let?s say it is being powered by a nearby generator that was installed for the sole purpose of running this motor. That way, we don?t have to think about any other equipment. You build a generator by wrapping wires around a core. You build a motor by wrapping wires around a core. Each of these sets of wires will have a magnetic field associated with it. When the motor is running, the magnetic field of the generator will exchange energy with the magnetic field of the motor. This is another example of a necessary evil, just like the one I described above. The motor can?t run without this energy exchange, but the energy exchange is not what is doing the work. There is something like a ?second current? that is allowing the motor to drive its load, to do its work.

When you see the power triangle that someone else mentioned, you are seeing the impact of the ?two currents.? There is the ?Reactive Power,? drawn on the power triangle as the vertical line, representing the energy exchange between the magnetic field of the generator and the magnetic field of the motor. There is also the ?Real Power,? drawn on the power triangle as the horizontal line, representing the work being done by the motor. Finally, there is the ?Apparent Power,? drawn on the power triangle as the slanted line, representing the net effect of the other two types of power.

Does this help?
 
charlie b said:
I like to introduce the concept this way. Most of us know that if you wrap a wire around a nail and attach a battery to the wire, you will have an electromagnet. You can use this ?tool? to pick up paper clips, for example. However, even before you try to pick up your first paper clip, there is current flowing through the wire, and there is a magnetic field that is not doing anything. You have to expend some amount of energy just to create the magnetic field.

When you start picking up paper clips, there will be more current flowing in the wire. The magnetic field is now doing some useful work. The total current in the wire can be treated as being two separate currents flowing at the same time. One current establishes the magnetic field. That one is almost a waste of energy (and money), in that you don?t get any work out of it. But you would not be able to do any work if it were not there. So it is something of a necessary evil. The second current is what is allowing the magnet to do its work.

The physical phenomena taking place in an AC circuit that has a power factor lower than 1.0 is analogous, to at least a small degree. Let?s consider a motor that has a power factor of 0.8. Let?s say it is being powered by a nearby generator that was installed for the sole purpose of running this motor. That way, we don?t have to think about any other equipment. You build a generator by wrapping wires around a core. You build a motor by wrapping wires around a core. Each of these sets of wires will have a magnetic field associated with it. When the motor is running, the magnetic field of the generator will exchange energy with the magnetic field of the motor. This is another example of a necessary evil, just like the one I described above. The motor can?t run without this energy exchange, but the energy exchange is not what is doing the work. There is something like a ?second current? that is allowing the motor to drive its load, to do its work.

When you see the power triangle that someone else mentioned, you are seeing the impact of the ?two currents.? There is the ?Reactive Power,? drawn on the power triangle as the vertical line, representing the energy exchange between the magnetic field of the generator and the magnetic field of the motor. There is also the ?Real Power,? drawn on the power triangle as the horizontal line, representing the work being done by the motor. Finally, there is the ?Apparent Power,? drawn on the power triangle as the slanted line, representing the net effect of the other two types of power.

Does this help?
Click to expand...
Much too convoluted.
The what it does rather why it does is the way to go for those who don't have and don't need electrical theory.
 
raiderUM said:
I think you hit the nail on the head.... I have struggled all weekend with different ideas and how to get the students to understand or take something away from my presentation. I believe I am going to just stick with basics. Show them some pictures of transformers, main distribution, and cap banks that we currently have at one of our academic buildings. I'll also go over some very basic electrical concepts like voltage, current, and use simple analogies to help them understand. After I go over these I'm sure half the class will be lost, so I might as well start in on cap banks and lose the other half. :blink:

I really think you are correct in saying I need to know my audience.... I want the students going into construction industry to take something away from this presentation, to at least know what a transformer looks like and an MCC. At least this way they can apply this in their future careers and know something about electric.
Click to expand...
Thank you for your kind words.
 
raiderUM said:
I want the students going into construction industry to take something away from this presentation, to at least know what a transformer looks like and an MCC. At least this way they can apply this in their future careers and know something about electric.
Click to expand...
Also make a demo of how power factor plays a role in real life by trying to analyse a POCO energy bill with power factor penalty.
 
Sahib said:
Also make a demo of how power factor plays a role in real life by trying to analyse a POCO energy bill with power factor penalty.
Click to expand...
That's a great idea, and include examples of why "power savers" are usually a scam.
 
Thank you all for the GREAT ideas! The presentation went well and hopefully the students learned something they can apply in their careers.

I ended up just doing a presentation of electrical blueprints, starting at the receptacle and working my way back to the main gear. I pointed out the capacitors and a very basic idea of what they did. The instructor thought the students would learn more this way, which I am sure he is right.

Again, thank you all for your input!!
 
PF presentation

PF presentation

I hope the grad students like this:

I have this nice cold bottle of beer. I get a tall glass and pour out the beer. Now you can see some beer froth at the top. I drink the beer and leave behind some of the froth.

Beer in bottle = kVA

Beer in glass = kW = one you actually drink

Beer froth = kVAR = you cant drink but still part of beer in bottle

how to improve power factor? less froth more beer !


- thanks to my colleagues here who introduced this presentation
 
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