In my country, the electricity generation and distribution provided by nation grid system is not sufficient and as a result the mains voltage drops down to 50 V r m s in certain regions where the norminal standard is 220V rms. Relay Type Voltage Regulators are widedly used by local people to step up the voltage to desired level around 220. In my opinion, the increased in numbers of using the Voltage Regulators is making the whole system to become more unstable. And I am thinking about a better solution for the power system instead of using Voltage Regulators. Any Suggesstions?
Voltage regulation at the local level is about all you can do, but if it is true that you are getting 50V when it should be 220V, you're stuck with a pretty bad system and your pushing it. Do you ever get near the nominal voltage (220V) or higher?
If the range is that wide... perhaps a custom-designed tap changer (for a transformer) might do the trick.
Not really - you are fighting basic physics - voltage regulators will remove the equipment's needed power from the grid, ands it will remove power in some combination of volts and amps. The regulators you describe sound like a very common type used in the US in the 1930s through the 1960s in automobiles, called "choppers" (and some other names) and were very reliable but had definite lives. I understand they are better for the grid, phasewise, than transformers.
Thinking out loud, Bottom line -
1) any time the power can be used, it will be removed from the grid
2) power is roughly amps times volts times phase shift.
3) If the transmission lines cannot deliver the demand power at the needed voltage, then there will be line losses and the user will see low voltage. If the demand remains even at the low voltage, there will be even more line losses, and even lower voltage, and even more line losses, etc.
i.e., - if the voltage can be held up at 220 volts at the using end, then for a given power delivery the amps will be held down and IR^2 losses in the transmission lines of that power will be held down. - as voltage drops, the amps must go up to satisfy the demand - and so do the losses in the transmission lines. E.g., drop the voltage to 110 volts, and the line losses are four times normal.
If everyone used transformers, the resulting phase shift would require a lot more amps - e.g., phase shift increases the amount of amps needed for the demanded power, and even a moderate amount of users using transformers and drawing down to 110 volts on a 220 system will increase transmission loss to eight-ten times or more normal
---------- On what basis? Choppers imply harmonics which bring in a whole new set of problems. Whether these are of concern depend on what is being upplied. ----------
------------ If you are assuming that the voltage has dropped to 110V and the transformer boosts to 220V to supply a xxKw load then it is true that primary current is doubled. Neither transformers or choppers will get around this.
If, as it appears by your clarification, you are assuming that the power demand is constant at all load voltages then I have to disagree. That is generally not true.
If the load is resistive, then the power demand will vary as the square of the voltage.
If the load is a motor, the power demand is reflected in other ways (and Ohm's Law is invalid)-by the mechanical speed torque characteristic of the load- which generally is not constant power. What happens then depends on a number of factors. Generally for an induction motor with such a drastic change in voltage- it either will not start or will stall under load (peak torque available about 1/4 that at twice the voltage). Yes the current will be higher than at rated voltage. How much- it depends. No one size fits all answer.
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----------- The phase shift in a transformer is actually quite small-ideally 0 but typically 2 to 3 degrees at rated load (based on a distribution transformer with 5% impedance). For a unity pf load this implies an input pf of 0.999 (increase in line loss of 0.1%). Now the phase shift due to multiple parallel transformers is about the same as with a single transformer and the change in line loss will be about the same 0.1% - no big deal. If you are considering cascaded transformers where phase shifts may be accumulative then there are other factors - such as "why do it if not needed for other reasons?" ----
----------- Take a look at the transformer on a pole near you- there is a fuse present. It isn't built into the transformer but hung near it on the primary side.
Don Kelly snipped-for-privacy@shawcross.ca remove the X to answer
C'mon - I quite specifically and clearly said phasewise, and vs transformers.
Please advise who said transformers or choppers would change the IE component of power....
I said what I said. "Any time the power can be removed from the grid, it will"
If a grid delivers a megawatt, it does not deliver a half megawatt if the voltage drops - rather, the voltage moves to the production capacity steady-state level of power.
fwiw- Ohm's law is never invalid - (that is why it is called a law.)
-by the mechanical speed torque characteristic of the
Odd comment, given the three major classes of ac motors are constant power, constant torque, and variable torque -
What a motor does or not do has nothing to do with the grid - the grid provides the power at its VA capacity - only as voltage and current, which thus makes phase important for power.
So Lenz law does not apply to transformers? Transformers with zero phase shift? Kind of blows that fundamental law...
Phase shift most certainly has been present in the double buck-boost transformers used in our industry for some 30 years, so much so that even though voltage was restored, actual power was even less than before the transfomers were installed.
fused ?? kind of like fused power supplies, where the fuse isn't inside the power supply so therefore the power supply isn't fused ????? or circuits having the fuse in the panel meaning that the outlet in the circuit isn't fused?
So a transformer is not a fused transformer unless the fuse is inside the transformer?
| If, as it appears by your clarification, you are assuming that the power | demand is constant at all load voltages then I have to disagree. That is | generally not true.
OTOH, it would be possible to build a device to provide constant voltage for a given range of input voltages at a certain maximum power level. It could be expensive, especially for a wider voltage range since at the lower end of that range it would have to pull much more current. Possible forms of such a device would include a mechanical variac with an automated motor that could compensate for low rate voltage swings (which the OP probably has).
I'd like to find a switching power supply for an ATX computer that can handle a voltage range much wider than the usual 100-250 volt continuous autoranging. Anyone make those commercially? I bet it would be quite expensive (particularly not being a commonly needed item). One that could operate on say 48-277 volts AC, 25-400 Hz, would be quite a design. Or let's go for 12-600 volts, 5-2000 Hz plus DC in either polarity :-)
When we finally see the shift from multi-DC-voltage to single-DC-voltage (probably 12 volts, but maybe a bit higher) power supplied to PC mainboards, they we should be able to see some better power control in computers.
| Take a look at the transformer on a pole near you- there is a fuse present. | It isn't built into the transformer but hung near it on the primary side.
A large battery/storage system that can charge slowly from the grid at various voltages. Then inverters or DC based loads to deliver power when desired.
Kind of like systems for poor performing wells. A key issue with V regulators is that they just pull down the distribution system when it's already having trouble. Ideally you want to make more effiecient use of the weakest parts of a system.
I've not tried this, but I would think there's a chance a wide ranging 100-250 volt supply would work below 100V providing you proportionally derate its power rating so you aren't exceeding the designed max input current rating. Obviously, there will be a point somewhere where it stops working.
PC supplies designed for Europe have PFC front end, but are designed for the high range 200-254V. If you could find a wide range supply with PFC (I ma not sure they are wildly available) it should work from 90 to 255 at full power AC, or DC regardless of polarity, since the PFC has a boost converter with an output of about 385VDC
At 45V it may still be able to deliver 50% of the power.
------ And you quite clearly are under the impression that phase shift in a transformer is a problem.
--------
---------- The grid tries to deliver the power demanded by the load. The load behaviour determines the voltage- current relationship and the power. Example: resistive load: R constant. Ohm's law applies and power will vary as the square of the voltage (1/4 power at 1/2 voltage). Example: Induction motor: load torque depends on speed in many cases but speed will not vary much. However, at half voltage, the peak and starting torques are 1/4 the normal values. If the motor can start, the peak torque will typically be half of full load torque. The motor will stall unless well below rated load is applied.
Go back and learn that Ohm's Law is, strictly applicable only to the situation where the resistance is constant. That is - a linear situation. In the case where resistance is dependent on voltage or current - it isn't valid even though E=RI , which is NOT Ohm's Law but is commonly called Ohm's Law in error, is valid but a bit awkward to apply as for R being dependent on current, as in a light bulb, then unless the current is known, you don't know R so you can find the current. A motor is an active load as it has an internal speed generated voltage as well as impedance. Ohm's Law doesn't apply. For your information see the following sites:
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's_law
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Note the "directly proportional" used by one and "linear" used by the other
--------- These are not motor classes- where did you get that? There are loads that are considered as approximately constant power or constant torque within reason. Most have torque varying with speed in a non-linear fashion. Synchronous motors have constant speed, torque and power determined by the mechanical load Induction motors are nearly constant speed and again torque and power are determined by the load. Sure a motor can be controlled to maintain constant torque or power but that isn't inherent to the motor.
--------- No. The grid supplies a voltage. The motor mechanical load determines its current at that voltage.The power required by a motor depends on its mechanical load which is not affected by power factor. The real part of the current is then determined by the load and the reactive part by the electrical characteristics of the motor. The current supplied by the grid depends on the motor and its load. >
------- It applies but I have said nothing to violate that. Lenz Law along with Faraday's Law simply say that the induced voltage in a coil is e= - N d(flux)/dt whatever the source of the varying flux. It can be (and is, for circuit analysis) considered as a voltage drop as seen from the supply -No big deal. As for the secondary, the voltage can be considered in phase or 180 degrees out of phase - depending on how you define the reference direction -i.e. polarity marks. For power transformers, primary current is taken as "in" at the polarity mark and secondary current "out" at the polarity mark. The polarity marks are set according to the voltages being in phase at no load.
Note that for an ideal transformer, with 0 magnetising current, no losses and no leakage reactance V1/V2 =N1/N2 =a and I1/I2/ =1/a So V1I1 =V2 I2 and since there are no losses, P1 =P2 Conservation of energy applies. It follows that reactive Q1 =Q2 in that case and that the power factor will be the same -no phase shift. For a real transformer, there will be losses, magnetising current and leakage reactance. For a typcial 5KVA transformer, the phase shift will be small as I indicated. This is easy to determine by experiment if you want to avoid theory. Find a good text on transformer and motor theory. One on circiut theory would help. .
-------- From diagrams of what appears to be your double buck boost transformers, it appears that what is being referrred to is a 4 winding transformer such as shown in
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The problem is not phase shift (which is negligable) but impedance -and trying a cheap fix to a problem rather than doing it properly by putting in an adequate supply.
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---------- Your definition, not mine. You are twisting words. Try reading what I said. Transformers are fused but the fuse is external to the transformer for several good reasons.
and this has what do do with your comment about "implying" and "a whole new set of problems" about phase and choppers?
Yes, that is what I said - it tries to deliver the load's requirements.
Since you keep making contrary comments to my statement where I said any time power can be removed from the grid, it will - apparently you are saying that anytime power can be removed from the grid, it won't?
Knock off the condescending crap - I taught it, wrote a book on circuits about using it, and had my EE and PE before you left high school - and go back learn it yourself, since you are not correct - First, it applies to impedance as well as resistance. It applies wherever the voltage-current line is linear, i.e., whenever a change in voltage does not change the impedance. That also means that if a conductor is only partially linear, it applies in the linear area of the conductor (in time or magnitude) In lay terms, it applies whenever the impedance does not change because of the applied voltage.
Second, laws are not invalid. Unlike theorems, there no proofs or derivations required of laws. However, any law of the sciences can be misapplied by those who do not know to what they apply -but that does not make the law invalid.
And lest you forget, you are the one arguing Ohm's law and the grid, not I ... I just said laws such as Ohm's law are never invalid.
incorrectly stated - but then, wikipedia is not a technical reference source
Even though internet sources are not rigorous technical sources, it got it right when it said
"The potential difference (voltage) across an ideal conductor is proportional to the current through it."
How can you even say that when the original poster said the 220 volt grid was supplying 50 volts?
No - the grid supplies power. No load - full voltage; moderate load - nearly full voltage; heavy load - brown voltage; very heavy load - very low voltage.
see the transformer experiment and phase shift-
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see power factor section of
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see section 8 on transformer efficiency (due to phase shift - aka power factor) - 85%
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It can be (and is, for circuit
Smoke and mirrors - phase shifts occur in circuits, not stand-alone devices; and phase shifts only occur when energy is transferred - thus an open transformer has no shift until it is connected to a load. Then it is an inductive device in an energy consuming circuit.
and thus no energy here, so there can be no phase shift. but hook the transformer to a load - and see about 85%.
No - the problem is real measured on-the-equipment phase shifts with a load attached to the transformers.
On 16 Dec 2006 20:51:37 GMT Andrew Gabriel wrote: | In article , | snipped-for-privacy@ipal.net writes: |> |> I'd like to find a switching power supply for an ATX computer that can |> handle a voltage range much wider than the usual 100-250 volt continuous |> autoranging. Anyone make those commercially? I bet it would be quite | | I've not tried this, but I would think there's a chance a wide | ranging 100-250 volt supply would work below 100V providing you | proportionally derate its power rating so you aren't exceeding | the designed max input current rating. Obviously, there will be | a point somewhere where it stops working.
I've heard this is not all that low, like around 80-85V. Great for people living in 220-240V parts of the world. This is one reason I want to migrate to running my computers on 240V instead of 120V (though the greater reasons include more efficiency). This is more complicated due to lack of good power handling equipment at this voltage such as surge protectors, UPSes, and PDUes that can handle and are safe with the US 240V (two opposing 120V lines) system. Most of the gain is lost if I have to convert the power to straight
240V (though that will probably open up the opportunity to use almost everything for power handling from Europe that can work with 60 Hz).
|> When we finally see the shift from multi-DC-voltage to single-DC-voltage |> (probably 12 volts, but maybe a bit higher) power supplied to PC mainboards, |> they we should be able to see some better power control in computers. | | Can't see why that would help.
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I'm envisioning them putting in a rack with several rows of blades and a pair of 12V-only power supplies at the bottom of the rack, each fed by
277V or 480V AC.
| |> When we finally see the shift from multi-DC-voltage to single-DC-voltage | |> (probably 12 volts, but maybe a bit higher) power supplied to PC mainboards, | |> they we should be able to see some better power control in computers. | | | | Can't see why that would help. | |
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Another good reason: computers are getting smaller and in many cases it is more practical to use an external power supply. I'd rather have a 2 or 3 wire cable going to my computer than the present dozen.
I don't know if 12 volts would be adequate as long as there is some need for direct regulated 12 volts. But there should at least be A STANDARD single DC voltage for this stage of power connectivity. And it needs to be somewhat of a voltage range coming in to accomodate battery usage.
On 17 Dec 2006 20:39:33 GMT Andrew Gabriel wrote: | In article , | snipped-for-privacy@ipal.net writes: |> On 16 Dec 2006 20:51:37 GMT Andrew Gabriel wrote: |>| In article , |>| snipped-for-privacy@ipal.net writes: |>|> When we finally see the shift from multi-DC-voltage to single-DC-voltage |>|> (probably 12 volts, but maybe a bit higher) power supplied to PC mainboards, |>|> they we should be able to see some better power control in computers. |>| |>| Can't see why that would help. |> |>
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| | Sorry, but that article is bullshit, unless US computer PSU's | are very much less efficient than the ones we've used in Europe | for the last 15+ years.
What efficiencies are you seeing? I do see efficiencies in PSU's are slightly higher when the input is 240VAC as opposed to 120VAC. But the idea I see here is to do this even better by having the voltages needed being regulated on the main board, and that supplied by a single DC voltage. A home computer built with such a board would have a PSU that converst 240VAC or 120VAC to that single DC voltage. This PSU being smaller can produce less heat. The mainboard won't have much more in regulators, so won't produce too much more heat, with the expected heat total being less than before. But for a data center, skip the PSU in each box altogether and have one per: (1) blade rack ... (2) cabinet ... (3) group of cabinets.
My question is, can this be done with a SINGLE DC VOLTAGE being THE standard voltage all computer mainboards use? Or does it have to be done with a different voltage for home users and data center users? If the latter, where's there cutover?
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