wat will the power dissipated be???

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cedance

Joined: 24 Oct 2003
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Location: Germany

12 Oct 2004 8:33 120v/60hz rate that energy is being dissipated

hi,

i actually dont know if this is a sensible question... nevertheless i ask it here hopin to get myself clear... Smile

say i have a 60 Hz voltage source and a device which draws 50 Hz current from it.. both are cosine functions.. then the integral of their products over the limits are '0' since the frequencies are different. (basic orthoganlity property).. does this mean that there would be no electricity bill for such an appliance??

/cedance

Last edited by cedance on 07 Mar 2005 16:26; edited 1 time in total

nicleo

Joined: 06 Sep 2004
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12 Oct 2004 9:00 power consumed power dissipated watts

Interesting ...

Do you mean the 60Hz voltage is the AC main (e.g. 120V/60Hz)?

Could you please elaborate more how do you carry out the integration? Thanks

echo47

Joined: 07 Apr 2002
Posts: 4206
Helped: 566

12 Oct 2004 9:44 ac power dissipated at time

That sounds like homework from my first-year "Circuits and Systems" class. Wink

Your strange device would spend half its time consuming power, and half its time generating power.
Work done is zero, so zero electricity bill.

However, the power company may frown upon what you are doing, and charge you for having a crazy power factor load!

Last edited by echo47 on 12 Oct 2004 10:00; edited 3 times in total

HCM_bucat

Joined: 29 Sep 2004
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12 Oct 2004 9:53 pwer useage power factor formula

I guess the key thing here is the power integration is 0. How can that be?

Big Boy

Joined: 20 Jan 2004
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12 Oct 2004 13:04 physics222project.pdf

It is possible for a device to take power on a 90 degree phase from the voltage. Both capacitors and inductors have this property.

If your load is only capacitive, or inductive, it will only dissipate power because of losses due to it's internal resistance. Appart from that, there can be large current flowing through that load, and take no power.

How this can be is because the voltave vs current is shifted 90 degree. You get the largest current drain where the voltage is zero. And current also get fed back to the source.

In a more day-to-day life (in real-life case), for ordinary applications, or small homes, this doesn't cause problems. However, if done on a larger scale, this can be a bit problematic. Taking current in this manner still put some load on the power company, and when you have a big company, with lots of motors, for examples, the electric co. have to take this into account, because the electric co still have to produce extra power. The electric company then also monitor the currect phase shift, and usually charge what thay call a 'phase penalty'. This is a bit like being charged for taking more than the allowed power, at a higher rate.

The power cables, running from the power facility to the end users, are very long (lots of miles of cables). The higher the frequency, the higher the cables act as an inductor. This is why the frequency is low (50 or 60 Hz), to minimize this problem. Even with low frequencies, with all the power lines, there is still a non-negligable inductances created over those lines. And the power co. have to take this into account. The inductive effect of an inductor can be eliminated by the capacitive effect of capacitors. Capacitors and inductors create an opposite effect. One take current 90 degree leading the voltage sine wave, the other 90 degree lagging the voltage wave. When combined, they cancel each others (they actually resonate togetter, but on the power source, they appear as an inert load). So, the power facilities have huge (and here I say *very huge*) capacitors at their line outputs. So, some people who also knew that thay had large capacitors, and they were thinking that those were to store electricity in case of brief power interruptions, this is a myth. Those caps are really for cancelling the inductive effect of the miles of power cables.

So, this is also why, on transformers, you usually don't see transformers rates like '10W' (10 Watt), but rather '10VA' which stand for 10 Volts-Amps. Although the power is the product of Volts x Amps (basic Ohm law), when applied to non-DC signals, as seen above, Power rating alone is not sufficient to rate the energy transfer capability of a transformer.

djalli

Joined: 10 Nov 2001
Posts: 887
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Location: 1600 Pennsylvania Avenue, Washington DC 20500

12 Oct 2004 13:23 power dissipated by inductor internal resistance

Here is something: Why you dont collect the free energy from power radiated in air by TV broadcastings, radios?

That power is truly indeed free. It will be small very small actually but imagine how cool is it.

and two pieces of articles to brighten your imaginations

Sorry, but you need login in to view this attachment

onemilimeter

Joined: 23 Sep 2004
Posts: 65
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12 Oct 2004 13:31 wat is power penalty

Big Boy wrote:

The power cables, running from the power facility to the end users, are very long (lots of miles of cables). The higher the frequency, the higher the cables act as an inductor. This is why the frequency is low (50 or 60 Hz), to minimize this problem.

Is this the only reason why the AC main power frequency was 'choosen' to be 50Hz or 60Hz? But why not 10Hz or 20Hz? Lower frequency, the eddy current losses at transformer also less. Why 50Hz or 60Hz? Is it choosen 'technically' or because of 'conventionally'?

djalli wrote:

Why you dont collect the free energy from power radiated in air by TV broadcastings, radios?

This sentence reminded me on RFID or SMART card. If I'm not mistaken, the RFID tag and SMART card both work on this principle, right?

------
What about generated electricity from 'earth magnetic field'? Is anyone doing research on this?
------

djalli

Joined: 10 Nov 2001
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Location: 1600 Pennsylvania Avenue, Washington DC 20500

12 Oct 2004 14:00 dissipated power inductor

onemilimeter wrote:

djalli wrote:

Why you dont collect the free energy from power radiated in air by TV broadcastings, radios?

True!

I think we leave alone earth magnetic field. Earth magnetic field is weak in short range , you can beat it, hence: notice magnetic levitation trains but this field is extremely powerful when you view/or use from great distances (example moon!).

Not forgeting of how much damage we have done to eco-system. Lets not play with this field otherwise if this field is gone (and it will be gone after some 600 or 800 centuries is predicted) earth is exposed to mercy of sun/cosmos radiation.

cedance

Joined: 24 Oct 2003
Posts: 704
Helped: 28
Location: Germany

12 Oct 2004 14:14 do dc signals dissipated power?

HCM_bucat wrote:

I guess the key thing here is the power integration is 0. How can that be?

nope... the integral is zero if u integrate two orthogonal functions of different frequency... the catch is not there i suppose... i got a convincing answer thou tha the whole thing is right that no power will be consumed!!! gr8! is it?

echo47 wrote:

However, the power company may frown upon what you are doing, and charge you for having a crazy power factor load

does the company sue u or the government?? ok... but if that is the case... u know for lowering the power dissipated people now use non-sinusoidal functions for both voltages or currents... (if i am right)... which will have the peak power higher but the average power is lesser than the conventional methods... these are all attempts to get the o/p power minimum as possible... so why should they sue?... we generate power for running a device,,, it works disspates no power... right...

/cedance

Last edited by cedance on 07 Mar 2005 16:29; edited 1 time in total

Borber

Joined: 01 Jan 1970
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12 Oct 2004 14:43 Re: wat will the power dissipated be???

The awerage value of product U*I is zero but the product of rms values gives the generated power because voltage is allways 230V AC and current let's say 1A AC. Power is not dependent on generators frequencies and is about 155W in this case. This is valid for parallel conection of voltage and current generators. I believe we are talking about effective power.

Last edited by Borber on 13 Oct 2004 19:27; edited 2 times in total

djalli

Joined: 10 Nov 2001
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Location: 1600 Pennsylvania Avenue, Washington DC 20500

13 Oct 2004 5:59 wat will the power dissipated be???

Electric companies (in USA) some of them have installed meters they can ping just the meter device if family has no power, any load is being applied,usage etc. In states in Midwest USA it is being applied.

They are far away towards a ferfect AMR automatic meter reading but they are saying they will go forward to this arena.

echo47

Joined: 07 Apr 2002
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13 Oct 2004 7:47 Re: wat will the power dissipated be???

Quote:

No, "sue" is the wrong word. On you next-month's electric bill, they may include an extra charge for your unusual load. Even though your kilowatt-hour meter reads zero, your current flow is still a burden on the electric company by heating up their transmission lines and transformers. They deserve a little money for that power loss.

If your unusual load is relatively small, the electric company probably won't care and won't charge you.

djalli

Joined: 10 Nov 2001
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Location: 1600 Pennsylvania Avenue, Washington DC 20500

13 Oct 2004 8:13 wat will the power dissipated be???

If you live in the country you can build possibly 2-3 km wire-wound antenna not very far to power lines go and "obtain" energy from these lines. Can this be detected very much? Or is a fancy imagination nobody will notice?

cedance

Joined: 24 Oct 2003
Posts: 704
Helped: 28
Location: Germany

13 Oct 2004 9:13 Re: wat will the power dissipated be???

djalli wrote:

similar to this question, i have one... light is an EM wave.. so keepin a magnet near it, does it get deflected?? with a meter can we measure it?? or energy onbtained from it??? is it possible? or u tend to say its very weak em field and so nothing possible.. ???

/cedance

Last edited by cedance on 07 Mar 2005 16:32; edited 1 time in total

cedance

Joined: 24 Oct 2003
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Location: Germany

13 Oct 2004 16:44 Re: wat will the power dissipated be???

nicleo wrote:

Interesting ...

Do you mean the 60Hz voltage is the AC main (e.g. 120V/60Hz)?
Could you please elaborate more how do you carry out the integration? Thanks

the integral is zero.. if so then the only way is the product of the cosine functions is zero.. which is the product of voltage and current.. = power.. so the power consumed is zero.. hope this gets ur doubt cleared.. reg. the integrations the integral of a cos * cos havin two different phases ( or frequencies).. u can always verify them to be '0'.... books on orthogonality properties would have this....

/cedance

Last edited by cedance on 07 Mar 2005 16:45; edited 1 time in total

me2please

Joined: 07 Aug 2004
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Helped: 64

13 Oct 2004 18:32 Re: wat will the power dissipated be???

I agree with echo 47 BUT I think you still have to pay. Why?
I think when your device generate energy back to the system, the meter won't roll backward for you. Razz

nicleo

Joined: 06 Sep 2004
Posts: 717
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13 Oct 2004 18:41 Re: wat will the power dissipated be???

djalli wrote:

My lecturer, specialised in power, shared with us his experience he gained from power plant. I still remember he told us that a fluorescent (both end connected to each other using a wire) can be 'turned on' if we put it (with the aid of a long stick) near to transmission line. He said he did it before.

cedance

Joined: 24 Oct 2003
Posts: 704
Helped: 28
Location: Germany

13 Oct 2004 19:28 Re: wat will the power dissipated be???

me2please wrote:

I agree with echo 47 BUT I think you still have to pay. Why?
I think when your device generate energy back to the system, the meter won't roll backward for you. Razz

wat if the first half of the time.. the device generated.. and the next half... the generated energy is being used.. instead the thinkin the opposite way.. ofcourse the first time i would consume a little power.. in which the meter is not goin to make that many rotations... Smile

/cedance

Last edited by cedance on 07 Mar 2005 16:50; edited 1 time in total

flatulent

Joined: 19 Jul 2002
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13 Oct 2004 20:11 Re: wat will the power dissipated be???

Meters based on a rotating disk will run backwards if power is put into the mains from your end. Back in the days of alternate energy some people in California USA would generate energy and put it into the mains. If they used less energy than this the meter would have a lower reading each time it was read. The state passed a law allowing this and also required the utility company to credit the house bill at a rate specified which was less than the rate charged for using energy.

The idea behind this was that it eliminated the storage battery cost and pollution from disposing of lead when the batteries ran out of storage capacity.

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13 Oct 2004 20:11 Ads

me2please

Joined: 07 Aug 2004
Posts: 362
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13 Oct 2004 21:06 Re: wat will the power dissipated be???

This is interesting! I never know exactly how the meter works.
Do you have any document that can help me learn more about
the meter, flatulent (or others)? Shocked

tochaHCM

Joined: 29 Sep 2004
Posts: 97
Helped: 1

13 Oct 2004 21:46 Re: wat will the power dissipated be???

You guy study too much and confused:
The simple formular for pwer is:

Power = Vrms * IRms * cosine(Phase angle between I and V)
integral of I or V are wrong. root mean square is the number

djalli

Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500

13 Oct 2004 22:18 wat will the power dissipated be???

I have another cooler idea. why do not do something to the meter to read slower? Not vandalizing it the meter but making meter read slower.

I know for sure without doubt this can be done.

HCM_bucat

Joined: 29 Sep 2004
Posts: 81
Helped: 3

13 Oct 2004 22:30 Re: wat will the power dissipated be???

That's a good idea. I want to save some money for my electric bill.

djalli

Joined: 10 Nov 2001
Posts: 887
Helped: 15
Location: 1600 Pennsylvania Avenue, Washington DC 20500

14 Oct 2004 0:10 wat will the power dissipated be???

In home or business electric bill savings? If it is home it would be peanuts indeed. Business do pay more for same amount of energy spent than homes in a lot of countries. Where I live small businesses like shops,restorants etc. pay 1.8 higher than homes do pay.
I live in eastern part of US and consume about 300kWatts monthly and cost me 35US dollars. You still can experiment for fun.

Speaking of utilities anyone has a book on legislation/rules overseeing middle man. Some companies provide the energy while buying it themselves from companies which have licenses to opeerate power plants.

Company I use for electric does not produces the electricity. They buy it. They have contract from US goverment to supervise,maintain relay/power line operations which they rent from US goverment and buy electricity from a nuclear power plant and sell it to us.

nicleo

Joined: 06 Sep 2004
Posts: 717
Helped: 60

14 Oct 2004 2:29 Re: wat will the power dissipated be???

me2please wrote:

This is interesting! I never know exactly how the meter works.
Do you have any document that can help me learn more about
the meter, flatulent (or others)? Shocked

You can find some interesting ONLINE facts regarding WH meter as belows:

http://www.public.iastate.edu/~dmumm/Physics222Project.pdf

http://www.utec.com/PDF/Bul_102.PDF

http://www.utec.com/PDF/v2hourmeters.pdf

http://www.watthourmeters.com/history.html

http://www.watthourmeters.com/

djalli wrote:

I have another cooler idea. why do not do something to the meter to read slower? Not vandalizing it the meter but making meter read slower.
I know for sure without doubt this can be done.

[Not Sure We Can Discuss This Issue In This Forum Or Not]
YES ... someone has done it. There are many ways to do it. One of them is to put a (strong) permanent magnet near to the meter to slow it down. My colleague from Indonesia (he worked in my country before) told me that in his country, there's a device that can 'stop' the meter running. The device allowed user to select the rotating speed (variable speed selector) of the disk in the meter. In our country, there is a 'LEGAL' device, which is claimed by the distributor to be able to SAVE electricity UP to 30%. However, we doubt it especially for single-phase supply.

tochaHCM wrote:

You guy study too much and confused:
The simple formular for pwer is:

Power = Vrms * IRms * cosine(Phase angle between I and V)
integral of I or V are wrong. root mean square is the number

Due to the increase of power harmonics in our electricity system, we probably need to use a MORE universal formula as follows:

Power = Sum(Vn x In x cosine(tn))
Vn and In are harmonic components, e.g fundamental, 2nd, 3rd, 4th, 5th, 6th,...etc; tn is the phase shift between each pair of Vn and In.

http://www.public.iastate.edu/~dmumm/Physics222Project.pdf wrote:

The type of kilowatt-meter that we will model is an induction-type that can only measure single phase AC current. The model is universal with respect to the various manufacturers (Westinghouse, Duncan, Shallenberger, Sangamo). We will assume that the current source and load contribute to a perfect sinusoidal waveform. Waveforms that are not ideal (contains harmonics) can affect the accuracy of any induction-type watt-hour meter."

I wonder whether the Watt-Hour meter (WHM), which wroks based on rotating disk, takes into consideration the harmonic contents of the electricity system or not. Old day AC analog voltage meter (multimeter), which works based on the excitatation of a small motor insides the meter, fails to give accurate result when the electricity voltage waveform is distorted (i.e. non-sinusoidal). Some digital multimeters also do not work well for non-sinusoidal signal (probably those meters assume the signal is sinusoidal). That's why we can see 'TRUE RMS' meter from Fluke or other manufacturers that really takes into account the harmonic contents of the electricity signal. I think 'digital' WHM is available in the market already.

sunsina

Joined: 13 Oct 2004
Posts: 45
Helped: 1

21 Nov 2004 6:32 Re: wat will the power dissipated be???

Yes, You didn't define How Your System Works.
Problem is Here your System works with 50 Hz but you have Connected that
to 60 Hz System .In Heating Systems in most cases you won't encounter any
problem but in AC Motor Systems the rpm is dependent to it's power frequency.

Now if you had used simple reactive elements such as Capacitor , Inductor ,transformer these elements only change the phase between their
Voltage and their Currents Phase 90 Degree (Lead Or Lag). But they Don't change
the input and output frequency (Eg from 60Hz to 50Hz).

Notice that Ideal Capacitors and Inductors are not Passive Elements
they stores Energy in Half a sine Period and Release the Stores Energy in the Second Half.

So Ideal Cap and Inductors Make Reactive Power .That's Why these Elements
takes more current from Power Line without Using it So if in your area there
are Many Of these Devices Like Motors (In Most Cases they are inductive ) the Power Distributer Company Will Install High Power Big Capacitors to Eliminates
the Phase Shifting Problem to Power Factor Near to 0.8-0.95.

In Industry as they Use Many Motors they Use two Kinds Of Power Meter:
1- Active Power Meter (Kilo Watts Hour)
2- Reactive Power Meter & Phase shift Meter (Kilo Vars Hour)

Although You Don't Use Reactive Power But it's a Penalty for you to Correct
your Power Factor about 0.8-0.9 (By Using Cap)

samehham

Joined: 24 Jul 2003
Posts: 20
Helped: 2

02 Mar 2005 5:00 Re: wat will the power dissipated be???

onemilimeter wrote

Quote:

if the frequence goes below 50 hz the lights and equipments will start to flicker since the voltage will vary from 0 to say 220 v fewer times in a second
notice that human eye will notice flickering if it is below 16hz also the transofmer size will icrease with lower freq, so 50 hz is a good compromise.