Erdős–Turán conjecture on additive bases: Difference between revisions

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[[File:Schematic induction regulator.svg|thumb|Schematic of wiring an induction regulator. Power source is connected to R-S-T rotor terminals. Output voltage is N+1-2-3 terminals.]]
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[[File:Diagram induction regulator.svg|thumb|Diagram of electrical [[phasor]]s for an induction regulator]]
An '''Induction regulator''' is a device, based on an [[induction motor]], which can provide a continuous ([[Analogue electronics|analogue]]) variable output [[voltage]]. In the past, it was utilized to control the voltage of electric networks. Nowadays, it has been replaced in this function by the [[Tap (transformer)|tap]] [[transformer]]. Its usage is now mostly confined to electrical laboratories, electrochemical processes and [[arc welding]]. With minor variations, its setup can be utilized as an isolator [[Quadrature booster|phase-shifting power transformer]].
 
==Construction==
It can be regarded as a wound [[induction motor]] utilized in pure electrical applications in comparison to the standard one which is electro-mechanical. Hence, the rotor does not normally turn, although it can be mechanically shifted by means of a [[worm gear]]. The rest of its constitution follows exactly a wound rotor [[induction motor]] as:
*slotted three-phase stator
*wound three-phase rotor, ends connected to accessible [[slip ring]]s plus common point (neutral)
 
Depending on the application, the ratio of number of turns between rotor/stator can vary.
 
==Working==
If the rotor terminals are connected to a [[three-phase electric power]] network, a [[rotating magnetic field]] will be driven into the [[magnetic core]].  
The resulting flux will produce an [[electromotive force|emf]] on the windings of the stator with the particularity that if rotor and stator are physically shifted by an angle α, then the electric phase shifting of both windings is α too. Considering just the fundamental harmonic, and ignoring the shifting, the following equation rules:
:<math>\frac{U_{stator}}{U_{rotor}}=\frac{\xi_{stator} N_{stator}}{\xi_{rotor} N_{rotor}}
</math>
 
Where ξ is the [[winding factor]], a constant related to the construction
of the windings.
 
Hence, if the stator winding is connected to the primary phase, the total voltage seen from the neutral (N) will be the sum of the voltages at both windings rotor and stator. Translating this to electric [[phasor]]s, both phasors are connected. However, there is an angular shifting of α between them. Since α can be freely chosen between [0, π], both phasors can be added or substracted. Obviously, all the values in between are attainable. Note that primary and secondary are not isolated. Also, the ratio of transformation between rotor/stator is constant. What makes the regulation possible is the angular shifting.
 
==Advantages==
The output voltage can be continuously regulated within the nominal range. This is a clear benefit against tap transformers where output voltage takes discrete values. Also, the voltage can be easily regulated under working conditions.
 
==Drawbacks==
In comparison to tap transformers, induction regulators are expensive, with lower efficiency, high open circuit currents (due to the airgap) and limited in voltage to less than 20kV.
 
==Applications==
An induction regulator for power networks is usually designed to have a nominal voltage of 14kV and ±(10-15)% of regulation, but this use has declined.  Nowadays, its main uses are in electrical laboratories and [[arc welding]].
 
==Bibliography==
{{cite book
  | last = Fraile-Mora
  | first = J. Jesús
  | authorlink = Jesús Fraile-Mora
  | title = Máquinas Eléctricas
  | publisher = [[McGraw-Hill]]
  | series =
  | year = 2003
  | doi =
  | isbn = 84-481-3913-5
  | pages = 358–359
}}
 
{{cite book
  | last = Serrano-Iribarnegaray
  | first = Luis
  | authorlink = Luis Serrano-Iribarnegaray
  | title = Fundamentos de Máquinas Eléctricas Rotativas
  | publisher = [[Marcombo Boixareu]]
  | series =
  | year = 1989
  | doi =
  | isbn = 84267070637 {{Please check ISBN|reason=Invalid length.}}
  | pages = 208–210
}}
 
{{cite book
  | last = Ras
  | first = Enrique
  | authorlink = Enrique Ras
  | title = Transformadores de potencia de medida y de protección
  | publisher = [[Marcombo Boixareu]]
  | series =
  | year = 1991
  | doi =
  | isbn = 84-267-0690-8
  | page = 160
}}
 
==See also==
*[[Variable frequency transformer]]
 
[[Category:Articles created via the Article Wizard]]
[[Category:Transformers (electrical)]]
[[Category:Energy conversion]]
[[Category:Electric motors]]
[[Category:Italian inventions]]

Latest revision as of 19:26, 2 October 2014

Is there a link between vision and learning? If one can see the print, is that the extent to which vision http://tinyurl.com/kecvhhb is beneficial, or does the process of learning require more than just the ability to see print?
When some Optometrists test a child with learning problems, the result often conveyed to parents is something along the lines of, "This child has 20/20 vision", cheap ugg boots or "This child sees perfectly well." The underlying implication is that, if a child can see, they should be able to learn, but anyone who's worked with learning disabilities as long as I have realizes that nothing might be further from the facts!

The Relationship Between Vision and Learning
Let's be clear from the outset, sight and vision are different. Sight is whether or not a kid sees the print, but vision goes beyond this, taking into consideration how they understand, interpret and absorb visual information. Let me illustrate. I am a fairly intelligent guy, university trained and quite experienced in life.

My distance vision is good (20/20 at the least), yet for a recent trip to Singapore, http://tinyurl.com/kecvhhb I saw a street filled with signs in Chinese, and I could not understand ANY of them! Not even one. I saw just fine, but could not even attempt to pronounce them, not to mention understand them!

In a sense, I don't possess the code for the written Chinese language. I can see it, but I cannot understand what the symbols mean. I can even copy it, but http://tinyurl.com/kecvhhb it really is without meaning to me. And for many children with learning problems, they experience something similar with English words.

Improve Vision and Learning Can Improve Too
If a child sees the print, I cannot really develop their sight. But if a child struggles to maintain their focus, or coordinate their eyes like a team, or if they can not remember the code or symbols, these we will help with. If they misread, mix up words or struggle to concentrate, this we can also help.

We can improve reading, writing and spelling but helping the kid to look at http://tinyurl.com/kecvhhb and absorb visual information comfortably and effectively. As a behavioural optometrist, this is exactly a place My group is obsessed with and may create a difference in in your child. We may help them overcome incredible odds in learning by improving their vision, versus just working with sight alone.

Frequently, the key about solving learning difficulties is improving a child's vision, and visual skills, and these two combined can prove the definite link between vision and learning.