There only thing magical is the belief that you are somehow being charged for power that you are not using. The meters work, they are accurate, the response is not altered by balance. If it is already accurately measuring your consumption, then how do you propose to alter the reading without somehow fooling it into an inaccurate reading?
Now it's starting to look like you're simply trolling here.
Does to me. Power companies aren't in the business of giving away energy.
You have it backwards. Power factor is P/VA. Power factor is a "fudge factor" that describes the difference between apparent power and real power. PF is not a physical entity and is not measured directly.
Right, as you were repeating here.
Torque * RPM = HP The motor (meter disk) is doing work.
Again, you have it backwards. PF is the conversion factor not what's being measured. POWER is being measured. Directly. No conversion needed.
Honestly, the only one here (ignoring Proteus) that doesn't understand this, is you.
Wierd way of looking at it, but sure. That's the way the meter is designed.
The power company would be stealing from you. That's not allowed any more than you stealing from them. Laws are funny that way.
It's NOT true, so saying "if it were" is a meaningless exercise.
No wannabees here. Well, perhaps you wannabe.
Of course it is. It's a promise that cannot be fulfilled. Hucksters sell this sort of magic pill all the time.
Sorry you feel that way, but what you're posting (and continue to post) is crap. That's not the way things work, as you've been told here by *everyone*. Your electrician friends need to go back to school (and I am being kind).
Several of the guys who answered you are probably EEs. They don't generally say much about it. Once in a long while, one might mention something he did in college or something about their certification. They don't have to brag about it. They'll generally know by reading each other's writing. They'll know in an instant I'm not one if the subject is at all technical. I didn't see much that looked like wise assed remarks. There wasn't anything close to the flames I've seen other places. People are just stating facts. The public service commissions or possibly the states' attorney generals should be all over this if it was real. I know scales at farmer's coops are tested for accuracy by the state. Gas pumps have stickers on them assuring their accuracy. States have bureaus of weights and measures to make sure things are according to hoyle. Why would they ignore the utility companies? What about all the lawyers running around? Think of the money a lawyer could make from a class action lawsuit if he won against a major utility. Here's a list of some of the things lawyers have sued for:
Dean
Not an EE, and I don't play one on TV.
From the very start this post was based on hearing that the meters run based on the power drawn from the high leg. Quote you "If it is already accurately measuring your consumption", if the meter recorded KWH of the high leg then it wouldn't be accurately measuring your consumption. If it were measuring high leg consumption X 2 then you could balance the load and use the power it was measuring, no magic involved. I'm not disagreeing that the meters are accurate, I heard they measured based on the high leg, hadn't heard this before, so I posted here. Many here gave good replies, others gave replies showing they didn't understand the question acting like I was looking for free power or something magical. So a meter doesn't read KWH based on the high leg, that's what I was trying to find out. However if a meter did work based on the high leg then balancing the load would let the consumer use more of the power they were paying for. Nothing free, just using what you're paying for. Some of these replies are on the line of claiming repairing a hole in your fuel tank is like stealing gasoline.
RogerN
If Power factor is P/VA then solved for P, P = Power factor X VA.
If you have a given torque on the meter disk, what limits the RPM? Is it generating a back EMF?
Well, I don't understand the stuff that's wrong.
There's lots of things a person can save money on or use more efficiently and it's not illegal even though it is pretty near stealing. One example is a 20oz soda often costs more than a 2 liter bottle of the same soda.
Nobody is selling anything, the guy telling this is not trying to get business balancing breaker boxes or anything like that. We work at as electrical techs in a factory repairing automated manufacturing machines, not wiring or rewiring houses.
Well, it was you that told me my calculation using power factor was wrong but then gave the same formula solved for power factor instead of power. My education was in electronics technology and we didn't go into the details of power meters and such, that is why I bring my question here. I don't have a problem being told that what I heard is not how a power meter works, I have a problem with those that try to tell me that a meter could not work that way or if it did then balancing the load would be like stealing electricity.
RogerN
Maybe you're not an EE but you gave a better reasoned answer than many. Stating that a KWH meter does not operate based on the highest leg is a good answer. Comparing balancing a breaker box to trying to steal electricity or a magically creating electricity is absurd.
I'm not an EE either but I did electrical controls design and programming for many years and still haven't used close to 10% of what I learned to get an AAS. I have worked for and with both PE's and EE's and have learned a lot from many of them, but not on utility meters, it was always more in the industrial automation field.
RogerN
None of us are telling you that meters *could* not work that way, or that *if they did* work that way you would not be correct. What we are telling you is that meters *don't* work that way, so speculating what to do if they did is like speculating if the moon were made of cheese how best prepare it to eat. We know that it's not, so why worry about what to do if it is?
Given the way meters *do* work (they accurately measure power used), getting them to read less (not accurate, false reading) is stealing power. If the meters were ever behaving in a manner that caused you to get billed for power you did not actually use, regardless of the load balance, that would be fraud on the part of the power company. Again, this is irrelevant outside of this imaginary situation because this is not how they actually work.
I'm not sure what is so difficult about this concept. There is nothing to optimize, the rest of the discussion is a hypothetical (imaginary) situation.
Go back and read over the replies again because nobody (aside from perhaps one of the trolls) has ever said that is the case. Trying to balance the breaker box is absolutely not stealing, nor is it magically creating electricity. The simple fact is that it will have zero measurable effect on the meter reading.
It was simply stated that since the meter already reads correctly, anything that did cause it to read slower (which does not include balancing) would be stealing power because given it already measures correctly, to get it to run slower without actually using less power would mean you are using some power that it is not measuring. Again, balancing your panel will *not* cause this to happen.
I agree, if meters are accurately measuring the power used then there is nothing optimize as far as the power bill, it would only help to get the full capacity from your service. I just don't understand when I post something about using the power I'm paying for (based on being misinformed about the operation of a power meter) others want to turn it into me wanting to steal power and such.
RogerN
No, there is a difference between the physical quantities measured and the conversion factor between them. You can't measure power factor, only derive it from power and VA.
Nothing limits RPM, other than the power measured. The whole idea is to measure the revolutions.
Yet you accuse engineers of not understanding electricity.
You're talking nonsense again.
These sorts of stories are often part of a sales pitch for magical savings devices, like "Watt Savers".
I didn't say your calculation was wrong, just that you had the horse before the cart. You don't measure PF directly. It's the difference between watts and volt-amps.
It *would* be stealing. In this case it would be the power company stealing form the consumer.
? "James Sweet" ?????? ??? ?????? news:helaij$ch3$ snipped-for-privacy@news.eternal-september.org...
The meter, is an electromeechanical integrator. It measures,integration calculus [from 0 to 2pi]tan (omega * t) dt where omega=2*pi*f (frequency in HZ=f) So, it's not to be fooled by trivial methods, like putting all loads to a high leg, etc. like some poster said, is like the elusive 100mpg carburetor, or fuel additives that increase mileage, etc.
What you heard from the" another electrician" was, purely and simply, BS. Balancing the load between legs is optimal with respect to losses but doesn't actually increase the KW capacity (not KWH) of the system. It just means that you can use the capacity slightly more efficiently. If you have a load of 15KW on one leg and 0 on the other, you will have more losses and poorer voltage regulation than if you have 7.5 KW on each leg. The meter simply measures what you actually use (+ losses on your side of the meter). Now the high leg metering X2 would be a cute but highly illegal trick that, along the way, would become apparent and the cost to the utility in class action suits would be prohibitive. Honesty in metering is something that is actually practiced. As to your torque without friction leading to infinite rpm- take a look at your meter- see those magnets which provide drag proportional to the speed of the disc? The result is that at any given torque, there will be a speed at which this torque is balanced by the drag. Adjustments to the meter does involve the positioning of these magnets. -- Not a wannabe
----- Don Kelly cross out to reply
I disagree with you regarding your interpretation of James Sweet's position. It was quite clear and correct. Otherwise I would have argued with him.
So if you have a 100A service I don't understand how having 100A X 120V is the same power as having 100A drawn from each leg, 100A X 240V. I would think at any given power factor 100A X 240V is more than 100A X 120V. I would think balancing the load so that you use 100A from each leg would increase your KW capacity of the service.
I certainly wasn't referring to you as a wannabe, you've always had good reasoning and explanations. But you've seen the others, perhaps they don't understand the question and give insulting smart-alecky replies and it's obvious from their reply that they either didn't understand the question or the subject they are replying to. Rereading James Sweet's posts I think he's right on too, but I don't agree that using the same KW's from each side of the line in is anything at all like magic bullets or 100mpg carburetors. But I think his point may be that those that sell misinformation about balancing the load saving money are in the same category as the 100mpg carb rip offs.
If meters measure true power then they are measuring VA X Power factor integrated over time, I was surprised no one took issue with krw stating that meters just measure true power and not VA X Power factor, since they are equal, but seems not according to krw. Also as explained with power producing torque in the disk I didn't understand how it controlled the speed of the disk unless their was also a drag or friction that controlled the speed. If you just apply a constant current to a motor the speed varies a lot according to load, doesn't seem to be useful for a meter unless, as you explained, there is a controlled drag or friction. If you make a constant current source and use it to supply a motor, the speed will change to keep the torque constant. If you have a constant voltage, torque (and current draw) will change to try to hold the speed constant. I know this varies according to type of motor, but even induction motors with variable frequency drives can use volts per hertz. Also stepper motors, though their speed is controlled by the step rate, they are capable of higher speeds with higher voltage.
RogerN
It isn't, that's not what he said. Think in terms of Watts, if you draw
100A at 240V that is twice the wattage as drawing 100A from 120V because with a 240V 100A load it is drawing 100A from each side. If your loads are so badly balanced that you are drawing 100A from one side and 20A from the other and it is a 100A service, you cannot add any more 240V loads. The capacity is there, but you are already at the max of 100A on one side. If you can shift some of the load over to the under utilized side then you will have freed up capacity, but you will not affect the reading of the meter by doing so. The important part, which is beating a dead horse at this point is that there is a coil on each leg, and both coils create torque on the same disk so whether you draw 100A on one side and 0A on the other, 50A on each side, 10A on one side and 90A on the other, it doesn't matter, in any of these situations the disk will see the same torque and turn the same speed, the only thing changing is which of the two coils supplies more of the total amount of torque. It doesn't matter if one box of rocks weighs 500 lbs and the other box of rocks weighs 100 lbs, if both boxes of rocks each weigh 300 lbs, or if one box weighs 600 lbs and other other is empty, if you put them both on a scale, it will read 600 lbs either way. Balancing the panel is taking rocks from one box and placing them in the other, it is not changing the total number or weight of rocks and will not affect the reading on the scale.
Yes they do measure true power, and no, they do not measure VA * PF over time, they are different. I think what is happening here is the common failure to differentiate between *equal to* and *equivalent to*. Volts * Amps * PF is *equivalent* to Watts (true power) but it is not *equal* to, it is not the same thing. Power can be measured directly, if you then know any two of the three other variables, Volts, Amps, and PF, you can calculate the third, but any one can be measured on its own without knowing any of the others.
Look at it this way, the speedometer in a car indicates vehicle speed in miles (or kilometers) per hour. This is equivalent to miles traveled divided by trip time, but it is not the same. Sure you could make a speedometer that recorded the distance traveled and time the vehicle was in motion and use that to calculate the speed in MPH and the answer would be right, but that isn't how real speedometers work. A mechanical speedometer, not to be confused with the odometer, has no concept of time or distance, rather it measures speed directly by magnetically coupled torque acting against a known friction, in this case a spring. In the same way, a mechanical power meter measures true power by energy passing through coils, causing a proportional amount of work to induce torque on the disk which rotates against a known amount of friction. In either case you have to have a known quantity of friction in order for the reading to have any meaning. Ignoring real world issues like insulation breakdown, a mechanical kWH meter doesn't know or care whether the voltage is 10V or 10,000V, rather it directly measures the amount of work being done by the power by acting on the disk with a proportional amount of work.
As for motors, there are many different types of motors, each with their own characteristics, and the sort of motor in a power meter is unlike any you're likely to find anywhere else. The reason stepper motors need higher voltage to achieve higher speeds is that the windings are inductive and it takes time for the current, and hence the magnetic field to build up. The faster the motor is turning, the less time you have per step, so the higher the voltage needs to be in order to create a magnetic field of a given strength in the time available. Similar reasons dictate the need to vary the voltage with the frequency of induction motors.
But if I read it correctly, that's what Don Kelly said. I think it's right in terms of KW but not in terms of 100A mains.
Quote Don Kelly "Balancing the load between legs is optimal with respect to losses but doesn't actually increase the KW capacity (not KWH) of the system. It just means that you can use the capacity slightly more efficiently. If you have a load of 15KW on one leg and 0 on the other, you will have more losses and poorer voltage regulation than if you have 7.5 KW on each leg."
I think Don Kelly was replying in terms of not exceeding the limit of 1 leg. If you had 100A main and a PF of 1 the limit should be 12KW from one leg or
24KW Total. So his example of 15KW would overload on one leg but be fine is balanced.That's how I understand it.
I understand this now, by original question was based on misinformation of the meter running at a speed based on only the high leg (X2). I had never heard that the meter ran based on the high leg (X2) before so I asked here and was informed of the misinformation.
But if the scale took the weight of the heavy box and doubled it (that would be like the misinformation I heard) then balancing the box would give you the true weight without cheating.
If they measure true power and not true power over time then how to they come up with KWH?
I realize it's not measuring everything independantly and performing calculations, but if it's measuring true power, the results would be equivalent VA X PF. In the formulas I've seen they use the equal sign (=) is their a different sign for equivalent?
The speed of the disk would be proportional to KW and counting the revolutions would be KWH. I don't see any direct way of reading KW unless you measure the speed of the disk. The electric meter would be more like an odometer accumulating total KWH used if I understand correctly.
RogerN
I disagree. Analog computers were around long before digital (the speedometer in a vintage car is an obvious one).
The three coils create a torque on the disk proportional to real power. The arrangement of the coils and inductance of the voltage sensing coil are such that the power factor *is* implicit in the development of the torque. A load current that is 90 degrees out of phase with the applied voltage results in no torque developed. (which is why many claims that 'power factor correction' will save you big money, are bogus)
If that were the only torque applied to the disk, it would spin rather rapidly because the mechanical friction is pretty small. And it would be hard to calibrate since the torque needed to drive all the gearing is somewhat variable. So another permanent magnet called a "drag magnet" is positioned next to the disk creates a counter-torque that is proportional to the disk's speed. Obviously the disk stops accelerating/decelerating when the torque produced by the sensing coils, friction and the drag magnet balance. The result is that the disk speed is proportional to the power in the sensing circuits.
(As an aside, some criminals have tried to cheat the power company by positioning additional 'drag magnets' above/below the disk. This tends to increase the counter-torque developed when the disk is in motion, slowing the speed of the disk for a given power level. The law does provide sanctions for such meter tampering.)
All the gears and wheels form an integrator (as in 'calculates the integral of the disk speed with respect to time'). Because the disk speed is 'revolutions / time', counting the revolutions is the calculus operation of integration with respect to time.
It's a meter that calculates the energy usage by sensing voltage, current and the phase relationship between them (i.e. power factor) and integrating the results over time.
daestrom
Certainly, but this doesn't change the fact that PF is not the measured quantity.
Yes.
Yes, others have clarified this better than I. I have no clue why he's still pursing this.
One could argue that such a speedometer 'calculates' the instantaneous speed by taking the derivative of distance. The turning of the speedo cable is a measure of distance. It drives the odometer directly. The magnet coupling develops a torque on the needle that is proportional to how fast the speedo-cable is turning (i.e. the derivative of distance traveled). The spring provides a counter-torque that converts the torque created in the coupling into a position (i.e. for a given coupling torque, the spring provides an exact counter-torque when the spring is stretched to one particular position). Just another example of an analog computer.
The way a kWh meter works is the reverse of this. It develops a torque proportional to VA*pf. Vary the power factor and the torque developed in the disk varies. A drag magnet develops counter-torque proportional to disk speed. The result is disk *speed* is proportional to VA*pf.
Your argument that the disk somehow measures power directly is false. The magnetic fields are created by a voltage sensing coil and two current sensing coils. Period. With these two magnetic fields, you don't have 'power', the best you have is VA. The meter shifts the phase of the voltage sensing field by 90 degrees by using a highly inductive coil. Then the three magnetic fields are arranged around the disk such that a torque is developed only when the fields sequence properly. That torque is maximized when the current is in phase with the applied voltage (one current coil's magnetic field leads the voltage coil's magnetic field by 90 degrees and the other current coil's magnetic field lags the voltage coil's magnetic field by 90 degrees).
Some commercial meters can be modified to measure VAR (V*A*sin(angle) instead of V*A*cos(angle)). They too only have current and voltage sensing coils, but by careful arrangement their magnetic fields interact with different timing.
daestrom
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