Author Topic: nobody talking about switching PS wasting power on input filter caps?  (Read 10757 times)

0 Members and 1 Guest are viewing this topic.

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #25 on: August 24, 2019, 11:54:37 am »
yes, but this "returned back" energy creates impedance change for power source. So, a power source (power plant) needs to spend more energy in order to fight with this "returned back" energy. Because this "returned back" energy will works against power source. Isn't it?

No. You do not understand the process. Two voltage sources in parallel are not working "against each other". They are "helping" each other.

Also, there is additional power loss in the capacitor and power loss in the wire, due to higher current. All this energy is lost and cannot be consumed. Yes, not all this loss happens inside capacitor, but this energy is wasted due to capacitor :)

Unless the capacitor is placed to compensate inductive rectance. But yes, poor power factor uses energy in the transmission wires regardless of the cause.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #26 on: August 24, 2019, 12:10:47 pm »
No. You do not understand the process. Two voltage sources in parallel are not working "against each other". They are "helping" each other.

There is no two voltage sources with the same voltage in parallel. On rise edge of sine wave, capacitor always have less voltage than mains and consume mains current for charging. On fall edge of sine wave capacitor always have higher voltage than mains and consume mains current for discharging. Mains voltage and capacitor voltage always shifted by some phase. So, they always working against each other.

Capacitor doesn't consume that energy. It just returns it back to AC generator. And AC generator needs to make an extra effort to charge and discharge this capacitor. It just waste some part of energy in order to charge and discharge this capacitor.

You can fix it by placing inductor, so it will make phase shift in the opposite direction. In such way AC generator will not needs to make an extra effort to charge and discharge capactior. But you will needs additional expenses on this inductor and heat loss in the wire between capacitor and inductor.

Exactly the same thing will happens with inductor connected to the mains. AC generator will needs to make an extra effort to fight against inductor. Inductor don't consume energy it just will return it back to AC generator (we don't talk about heat loss in the wire). And AC generator will needs to fight agains "returned back" energy from inductor. In order to fix it you will need to place capacitor to make phase shift in the opposite direction.
« Last Edit: August 24, 2019, 12:35:48 pm by radiolistener »
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #27 on: August 24, 2019, 12:40:59 pm »
Unless the capacitor is placed to compensate inductive rectance.

The same you can place inductor to compensate capacitive resistance. But this compensating inductor or capacitor requires additional expenses and needs to be connected together with reactive load. If you don't place such capacitor/inductor, AC generator will needs to make additional effort to work against your reactive load. Who will pay for that? :)
 

Offline JohnG

  • Frequent Contributor
  • **
  • Posts: 586
  • Country: us
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #28 on: August 24, 2019, 01:31:03 pm »
Wikipedia is your friend: https://en.wikipedia.org/wiki/Power_factor

John
"Reality is that which, when you quit believing in it, doesn't go away." Philip K. Dick (RIP).
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3229
  • Country: be
    • Freelance Hardware Engineer
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #29 on: August 24, 2019, 02:00:19 pm »
Unless the capacitor is placed to compensate inductive rectance.
If you don't place such capacitor/inductor, AC generator will needs to make additional effort to work against your reactive load. Who will pay for that? :)

Depends on your definition of effort. A genset consists of some kind of motor and the actual generator. The motor doesn't care. Whatever extra effort it needs to do is returned. The generator *does* care, but only because of the current. It's the current that heats up the winding and it's the maximum temperature of that winding that will determine the maximum VAR of that generator. So in theory, you can load the generator up to its maximum while the attached motor is still idling (except for the I²R losses and provided the motor has sufficient inertia to load/unload).
 

Online Circlotron

  • Super Contributor
  • ***
  • Posts: 3364
  • Country: au
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #30 on: August 24, 2019, 02:01:10 pm »
On rise edge of sine wave, capacitor always have less voltage than mains and consume mains current for charging. On fall edge of sine wave capacitor always have higher voltage than mains and consume mains current for discharging.
No. On the falling edge of the sine wave the capacitor supplies current back to the mains, it does not consume current. It only consumes current on the rising edge of the mains.
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #31 on: August 24, 2019, 02:15:30 pm »
No. On the falling edge of the sine wave the capacitor supplies current back to the mains, it does not consume current.

On falling edge capacitor prevents AC generator to decrease voltage. Because when AC generator trying to decrease voltage, capacitor provides it's own voltage and prevents voltage drop in such way, so AC generator needs to apply more power in order to overcome capacitor resistance.

It only consumes current on the rising edge of the mains.

It consume current on both edges. You're forgot that we're talking about AC voltage. AC voltage means that current change it's direction in a loop.

On rise edge AC generator provides +current, and capacitor consumes -current in order to charge.

On falling edge AC generator provides -current, and capacitor consumes +current in order to discharge.

In simple words, capacitor prevents AC generator to change voltage in both direction and AC generator needs to consume more mechanical power in order to make AC voltage.

Capacitor don't consume energy (except heat loss in the wires), but it makes phase shift, so AC generator will needs to fight with it's own energy returned back (which creates additional load for AC generator). This returned voltage prevents AC generator to change voltage in order to make AC voltage.

The same issue with inductor. Inductor don't consume energy (except heat loss in the wires), but it makes phase shift in opposite direction, and it leads to the same result as with capacitor - AC generator will needs to fight with it's own energy returned back (which creates additional load for AC generator).

When you connect capacitor and inductors together, they will compensate phase shift of each other, and it will reduce power load on AC generator. But even in this case it still has higher heat loss on wires between capacitor and inductor.
« Last Edit: August 24, 2019, 03:08:14 pm by radiolistener »
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3229
  • Country: be
    • Freelance Hardware Engineer
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #32 on: August 24, 2019, 03:10:50 pm »
I appologise for the crudity of the drawing (and thank you darling for lending me your crayons) but this may help you understand. Or not.
 
The following users thanked this post: tooki

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #33 on: August 24, 2019, 03:33:14 pm »
Ice-Tea, AC generator needs to change voltage from + to - and then again to + and then again to - in a loop.

Capacitor prevents that voltage change, it trying to make constant 0 V from AC voltage. Try to understand that when AC generator trying to reduce voltage (on the falling edge of sine wave), the capacitor will prevent that by providing it's accumulated energy.

Capacitor will use it's accumulated energy in order to prevent voltage change (basically to stop AC generator). This energy returned by capacitor will be consumed by AC generator to stop rotation of AC generator rotor. And you will need to apply more mechanical power to AC generator rotor. For example it will leads to higher gasoline consumption, if you're using gasoline AC generator.

As you can see, capacitor doesn't consume this energy, but when you connect it to AC generator it lead to waste additional power in the AC generator, because capacitor prevents AC generator to make voltage change in any direction.

In short, capacitor uses AC generator energy against AC generator. So, AC generator first needs to waste some power in order to charge capacitor and then it needs to waste some power again to discharge capacitor. And this happens 50 times per second.
« Last Edit: August 24, 2019, 03:39:42 pm by radiolistener »
 

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #34 on: August 24, 2019, 03:34:57 pm »
On falling edge capacitor prevents AC generator to decrease voltage. Because when AC generator trying to decrease voltage, capacitor provides it's own voltage and prevents voltage drop in such way, so AC generator needs to apply more power in order to overcome capacitor resistance.


You are totally wrong here but this thread has degenerated into such confusion that I am going to bow out and let others deal with the confusion because this is like shooting at clouds.

I do not know what your qualifications are but I can tell you are not an Electrical Engineer. There are some of us on this board who are engineers. You should listen to them.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3229
  • Country: be
    • Freelance Hardware Engineer
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #35 on: August 24, 2019, 03:52:39 pm »
Ice-Tea, AC generator needs to change voltage from + to - and then again to + and then again to - in a loop....

I have no idea how to explain this to you. However, you will not find anyone on this board or on another tech-savvy forum that agrees with you. Unless it's called "Free Energy For All" or something. This should tell you something. And perhaps it should bring you to read up on the subject.
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #36 on: August 24, 2019, 04:02:01 pm »
You are totally wrong here

Can you please explain, what is wrong exactly?

I'm talking that reactive load, such as capacitor or inductor will return some part of power back to the AC power source. This power will be used against AC power source.

In simple words, capactior trying to filter AC voltage and make DC. On the contrary AC generator trying to make AC voltage. So they fight each other.

What is wrong here?
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3229
  • Country: be
    • Freelance Hardware Engineer
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #37 on: August 24, 2019, 04:09:49 pm »
I'm talking that reactive load, such as capacitor or inductor will return some part of power back to the AC power source.


Yes.

Quote
This power will be used against AC power source.

No. Look at the diagram I posted earlier. The power returned to the source takes load *off* it, it doesnt add to it.
« Last Edit: August 24, 2019, 04:16:56 pm by Ice-Tea »
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #38 on: August 24, 2019, 04:44:37 pm »
Eventually perhaps it will sink in and you will understand what we are trying to say. Until then just accept that a reactive load does not cause the generator to draw more mechanical energy from the engine, turbine or whatever is driving it, beyond the small percentage that becomes heat in the windings and wiring. The fact that you do not grasp how this can happen does not make it any less true. It is easily demonstrated though if you can find a portable AC genset and some capacitors or inductors.
 
The following users thanked this post: tooki

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #39 on: August 24, 2019, 04:45:52 pm »
I have no idea how to explain this to you. However, you will not find anyone on this board or on another tech-savvy forum that agrees with you. Unless it's called "Free Energy For All" or something. This should tell you something. And perhaps it should bring you to read up on the subject.

There is no "Free Energy For All" at all, there is only wasted energy.


No. Look at the diagram I posted earlier.

Just imagine DC battery with + and - terminals. And capactior with A and B terminals.

Now connect DC battery to capacitor: + to A and - to B. The capacitor will be charged.

Now connect DC battery to capacitor with reversed polarity (this is how AC current works): - to A and + to B. The capacitor first will be discharged through DC battery and then charged to reversed polarity.

Let's assume that capacitor charge takes energy E from battery. So, during experiment you spent 3*E energy (charge+discharge+charge) from DC battery. But capacitor stores just 1*E energy. So, you're lose 2*E energy.

And note, this energy is NOT consumed by capacitor. It is consumed by DC battery. This is wasted energy of DC battery.

The same things happens with AC generator with connected capacitor on the output.

On rise edge of sine wave capacitor will be charged from AC generator. On falling edge of sine wave capacitor will be discharged to AC generator and then charged again in reverse polarity. It happens in a loop.

As you can see, on falling edge capacitor will be discharged to AC generator.

It means that current from capacitor (which flows through AC generator) will make resistance to mechanical rotation. And you will spend more gasoline for AC generator rotation. You're just wasted that energy.

This is something like use gasoline to move car from point A to point B and then move it back to point A. Gasoline wasted and the car is staying at the point where it was before :)
« Last Edit: August 24, 2019, 04:49:07 pm by radiolistener »
 

Offline Ice-Tea

  • Super Contributor
  • ***
  • Posts: 3229
  • Country: be
    • Freelance Hardware Engineer
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #40 on: August 24, 2019, 05:07:42 pm »
Just imagine DC battery with + and - terminals. And capactior with A and B terminals.

Now connect DC battery to capacitor: + to A and - to B. The capacitor will be charged.

Now connect DC battery to capacitor with reversed polarity (this is how AC current works): - to A and + to B. The capacitor first will be discharged through DC battery and then charged to reversed polarity.

One more try. Look at the diagram. What you are describing is 2 phases out of 4. There where you have a positive voltage and you're charging the cap (first 90° section, postive voltage positive current) and there where you have a negative voltage and charging the cap (to a negative voltage) (third 90° section, negative current and negative voltage). This does not take into account to the two other sections that have postive voltage and negative current and the part where the voltage is negative and the current positive.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #41 on: August 24, 2019, 05:26:59 pm »
There is no wasted energy. Rather than making an ass of yourself by insisting there is against several people who know what they're talking about, go try it yourself. Find a small portable backup generator and connect some large capacitors across it. You can monitor the engine load by listening to the sound it makes.

Another method to prove there is no wasted energy is take a bunch of capacitors, wire them in parallel and place them inside an insulated styrofoam cooler with a temperature sensor and connect it to the mains. Measure the current draw and calculate the apparent power, then record the temperature rise over a period of say 30 minutes.

Now find an incandescent lamp that will draw roughly the same current as the capacitor bank and place it in the same box, repeating the experiment in place of the capacitor bank. You will find that the lamp results in a dramatic temperature rise while the capacitors do not and this can only mean one thing, the lamp is consuming energy and the capacitors are not. Energy cannot be created or destroyed, for energy to be wasted something has to heat up.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20363
  • Country: gb
  • 0999
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #42 on: August 24, 2019, 05:40:19 pm »
I have no idea how to explain this to you. However, you will not find anyone on this board or on another tech-savvy forum that agrees with you. Unless it's called "Free Energy For All" or something. This should tell you something. And perhaps it should bring you to read up on the subject.
(Attachment Link)

There is no "Free Energy For All" at all, there is only wasted energy.


No. Look at the diagram I posted earlier.

Just imagine DC battery with + and - terminals. And capactior with A and B terminals.

Now connect DC battery to capacitor: + to A and - to B. The capacitor will be charged.

Now connect DC battery to capacitor with reversed polarity (this is how AC current works): - to A and + to B. The capacitor first will be discharged through DC battery and then charged to reversed polarity.

Let's assume that capacitor charge takes energy E from battery. So, during experiment you spent 3*E energy (charge+discharge+charge) from DC battery. But capacitor stores just 1*E energy. So, you're lose 2*E energy.

And note, this energy is NOT consumed by capacitor. It is consumed by DC battery. This is wasted energy of DC battery.

The same things happens with AC generator with connected capacitor on the output.

On rise edge of sine wave capacitor will be charged from AC generator. On falling edge of sine wave capacitor will be discharged to AC generator and then charged again in reverse polarity. It happens in a loop.

As you can see, on falling edge capacitor will be discharged to AC generator.

It means that current from capacitor (which flows through AC generator) will make resistance to mechanical rotation. And you will spend more gasoline for AC generator rotation. You're just wasted that energy.

This is something like use gasoline to move car from point A to point B and then move it back to point A. Gasoline wasted and the car is staying at the point where it was before :)
Your battery analogy is flawed because it's a square wave, which will theoretically cause infinite current to flow when the polarity is reversed. In reality the power will be dissipated in the internal resistance of the battery and capacitor. The mains is sinusoidal, so you're not comparing like with like.

Look at what happens when the power drawn from V1 is plotted in LTSpice. It starts at zero, gradually goes more negative (in this case a negative number is power being taken from V1)), reaches a peak at 45º, then falls to zero again and climbs to positive, as the energy stored in the capacitor is returned to V1. Note, that average power taken from V1 is zero, over the entire waveform. No one is claiming perpetual motion.


In real life there will be some resistance which will dissipate power and cause the generator to work harder, but it won't be as extreme as with a square wave. The mains also typically has many inductive loads, such as motors and lightly loaded transformers, so a little bit of capacitance will help to bring the power factor closer to unity.
« Last Edit: August 24, 2019, 05:42:15 pm by Zero999 »
 
The following users thanked this post: tooki

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #43 on: August 24, 2019, 05:43:13 pm »
Eventually perhaps it will sink in and you will understand what we are trying to say. Until then just accept that a reactive load does not cause the generator to draw more mechanical energy from the engine, turbine or whatever is driving it, beyond the small percentage that becomes heat in the windings and wiring. The fact that you do not grasp how this can happen does not make it any less true. It is easily demonstrated though if you can find a portable AC genset and some capacitors or inductors.

You know, it just occurred to me that what he is saying is, in a way, the same as the free energy crowd. They say they can make energy appear out of nowhere and radiolistener is saying energy disappears which is just as impossible. Energy can be stored but it cannot be made to disappear. Energy can be converted to heat and that is precisely the question of the OP: why do capacitors that are apparently consuming power do not get hot? And the answer is because they do not consume power, they store power and then return it. If they "wasted' it then it would be converted to heat.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #44 on: August 24, 2019, 05:44:36 pm »
One more try. Look at the diagram.

Ok, let's look at diagram.

We have 311 Vpk 50 Hz AC source loaded with 31.83 uF capacitor (100 Ohm at 50 Hz).

So, let's look at diagram of power consumption for AC source:

green diagram = voltage on AC source
red diagram = power consumption on AC source

818898-0

As you can see, AC source first feeds capacitor with generated power (negative power consumption), and then AC source consume power from capacitor (positive power consumption). 

What happens with power consumed by AC source?

I provided you with answer - this power will be used against AC generator. In simple words this power will be used to stop rotation of AC generator rotor. In order to continue AC generating you're needs to apply more mechanical power to AC generator.

This is my explanation. So, what is your explanation, what is happens with power consumed by AC source?   :)
« Last Edit: August 24, 2019, 06:04:18 pm by radiolistener »
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #45 on: August 24, 2019, 05:58:16 pm »
Note, that average power taken from V1 is zero, over the entire waveform.

Yes. And my explanation is that this energy is consumed by AC source and it makes rotation of AC generator more hard. You're needs to apply more mechanical energy to keep AC voltage.

But Ice-Tea, soldar and james_s claiming that this energy is not consumed by AC source and it doesn't change load resistance for AC source. So technically they claimed that there is perpetuum mobile or some kind of free energy  :)

So who is right?
« Last Edit: August 24, 2019, 06:05:34 pm by radiolistener »
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20363
  • Country: gb
  • 0999
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #46 on: August 24, 2019, 06:12:54 pm »
Note, that average power taken from V1 is zero, over the entire waveform.

Yes. And my explanation is that this energy is consumed by AC source and it makes rotation more hard. You're needs to apply more mechanical energy to keep AC voltage.
If the power is zero, then why would more mechanical energy be required?

Quote
But Ice-Tea, soldar and james_s claiming that this energy is not consumed by AC source and it doesn't change load resistance for AC source. So technically they claimed that there is perpetuum mobile or some kind of free energy  :)

So who is right?
You're wrong.

No, they're not claiming free energy.

Quote
What happens with power consumed by AC source?

I provided you with answer - this power will be used against AC generator. In simple words this power will be used to stop rotation of AC generator rotor. In order to continue AC generating you're needs to apply more mechanical power to AC generator.

This is my explanation. So, what is your explanation, what is happens with power consumed by AC source?

There's a clear gap in your understanding. You haven't considered the fact that the alternator can also work as a motor. Take energy out of it and put it into the capacitor and it will increase the load on the engine. Put energy back into it, from the capacitor and it will reduce the load on the engine. The mechanical inertia will smooth this out so it will behave as if there's no mechanical load.
« Last Edit: August 24, 2019, 06:15:26 pm by Zero999 »
 

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #47 on: August 24, 2019, 06:20:44 pm »
Yes. And my explanation is that this energy is consumed by AC source and it makes rotation of AC generator more hard. You're needs to apply more mechanical energy to keep AC voltage.

This is wrong.

Photo of capacitors in substation:
https://en.wikipedia.org/wiki/File:Condensor_bank_150kV_-_75MVAR.jpg
They don't put them there so they can waste energy.
« Last Edit: August 24, 2019, 06:28:42 pm by soldar »
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #48 on: August 24, 2019, 06:38:09 pm »
If the power is zero, then why would more mechanical energy be required?

Because energy generated with AC generator rotation was accumulated by capactior and then returned back to AC generator. AC generator consumed returned energy to make rotor rotation more hard.

So, if you don't apply more energy, rotor will slow down and stop and AC voltage will drops down to zero. In order to keep AC voltage at 311 Vpk 50 Hz, you're needs to apply more power.


There's a clear gap in your understanding. You haven't considered the fact that the alternator can also work as a motor.

I considered that. But it can works as a motor if you feed it with in-phase AC. Which is not the case for capacitor. Capacitor feeds AC generator with phase shifted AC.

If AC generator rotating clock wise, the capacitor will feed AC generator in such way so it will rotate counter clock wise.

Just look, if it works like you say, it will turns into perpetuum mobile, which is not possible. It doesn’t bother you?
« Last Edit: August 24, 2019, 07:03:20 pm by radiolistener »
 

Online radiolistener

  • Super Contributor
  • ***
  • Posts: 4135
  • Country: 00
Re: nobody talking about switching PS wasting power on input filter caps?
« Reply #49 on: August 24, 2019, 06:42:50 pm »
This is wrong.

Photo of capacitors in substation:
https://en.wikipedia.org/wiki/File:Condensor_bank_150kV_-_75MVAR.jpg
They don't put them there so they can waste energy.

They needs to remove reactive component from the load impedance. If load already don't have reactive component, they don't needs and don't used.

Do you know that load may have reactive component in it's impedance?
« Last Edit: August 24, 2019, 06:54:59 pm by radiolistener »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf