Lattice of subgroups: Difference between revisions

From formulasearchengine
Jump to navigation Jump to search
en>RedBot
m r2.7.2) (Robot: Adding pl:Krata podgrup
 
en>Mate2code
m use diagram with cycle graphs
 
Line 1: Line 1:
== Nike Tn Pas Cher Suisse ==
{{two other uses|ripples in electricity|ripples on fluid interfaces|capillary wave||ripple (disambiguation)}}


Si ce n'est pas alors un [http://www.treffpunkt-innenstadt.ch/includes/lang/error.asp Nike Tn Pas Cher Suisse] accord, tout le monde va se précipiter pour retirer leur argent. Le système financier tout s'écroulera.. La pièce [http://www.walzehuser-buehni.ch/controls/base.asp Nike Geneve] maîtresse de l'approche du site sera à sa santé "voyages", un contenu riche sur les conditions de santé les plus commonlysearched. Chaque voyage mettra en vedette un large éventail de contenu, y compris des témoignages de patients, les conseils du médecin et de l'information clinique. <br><br>Éducateurs vision prospective développées dans l'exercice de problème en temps réel résoudre sur une base quotidienne. Il est temps de consulter le cognoscente, gouverneur. Budget de la défense est de plus en plus robuste tout comme Washington peut moins se le permettre, avec un vieillissement de la population exigeant bientôt leur retraite promise et bienfaits pour la santé, les législateurs et les analystes indépendants dit. Sénat le mercredi était prête à approuver près de 460 milliards de dollars pour permettre au Pentagone de payer les soldats, acheter des armes et faire de la recherche au cours des 12 prochains mois.. <br><br>Beaucoup de fruits en plus de baies d'açai fournissent des antioxydants et autres nutriments qui sont importants pour votre santé. Mais si vous voulez essayer d'açai, vérifiez vos aliments de santé local ou magasins gastronomiques açai peuvent être consommés crus, sous forme de comprimés, dans des boissons telles que jus, smoothies ou boissons énergétiques, ou dans d'autres produits alimentaires tels que la gelée ou de crème glacée . <br><br>Si c'est vous et que vous souhaitez retirer, puis cliquez sur ce lien. Arvind Pachhapur est la gestion de l'ingénierie logicielle pour Thomson Reuters, une organisation qui a sa base dans Dexter, MI. Cela a été une expérience incroyable. J'ai eu la chance de gérer certains des plus grands joueurs de ce pays, sans parler de Manchester United. <br><br>Vous acceptez également de ne pas adapter, modifier ou créer une œuvre dérivée de tout contenu de ce site Web, sauf pour votre usage personnel et non commercial. Toute autre utilisation du contenu de ce site nécessite l'autorisation écrite préalable de BBCW. <br><br>San Francisco nervure nécrologique mémorial gilet meilleurs garçons [http://www.angelforce.ch/content/gallery/class.asp Nike Air Force] d pendants merl prévu [http://www.reinmedical.ch/archiv/system/lib/system.php Nike Free Suisse] sur tia grand canapé de mon toyota. Canby gymboree Fla Sher animal de compagnie à Cape lFasher Mossman pour le diamant d argent de la forêt tropicale. Cette propriété, connue dans le secteur forestier comme "baseage invariant», se réfère à deux aspects différents de la modélisation de l'indice du site: baseage équation invariante et baseage méthode d'estimation invariant (BAI), introduit par Bailey et Clutter (1974). Cette propriété n'est valide que si aucun terme d'erreur aléatoire est considéré.<ul>
The most common meaning of '''ripple''' in [[electricity|electrical science]] is the small unwanted residual [[periodic function|periodic]] variation of the [[direct current]] (dc) output of a power supply which has been derived from an [[alternating current]] (ac) source. This ripple is due to incomplete suppression of the alternating [[waveform]] within the power supply.
 
  <li>[http://pedagogie-differenciee.eu/spip.php?page=auteur&id_auteur=1&lang=fr/ http://pedagogie-differenciee.eu/spip.php?page=auteur&id_auteur=1&lang=fr/]</li>
 
  <li>[http://verdamilio.net/tonio/spip.php?article303/ http://verdamilio.net/tonio/spip.php?article303/]</li>
 
  <li>[http://enseignement-lsf.com/spip.php?article369#forum24679806 http://enseignement-lsf.com/spip.php?article369#forum24679806]</li>
 
  <li>[http://ciarcr.org/spip.php?article310/ http://ciarcr.org/spip.php?article310/]</li>
 
  <li>[http://www.film-video-dvd-production.com/spip.php?article6/ http://www.film-video-dvd-production.com/spip.php?article6/]</li>
 
</ul>


== Ceinture Hermes Suisse ==
As well as this time-varying phenomenon, there is a '''[[frequency domain]] ripple''' that arises in some classes of [[filter (signal processing)|filter]] and other [[signal processing]] networks. In this case the periodic variation is a variation in the [[insertion loss]] of the network against increasing [[frequency]]. The variation may not be strictly linearly periodic. In this meaning also, ripple is usually to be considered an unwanted effect, its existence being a compromise between the amount of ripple and other design parameters.


Responsive design sera le moment [http://www.raceland.ch/content/blog/publish.asp Ceinture Hermes Suisse] fonctionne pas avec les applications de messagerie comme Gmail ou Yahoo Mail. membre de la bande de Maestro, Morten Veland, a guidé et orchestré SIRENIENS d'être un des artistes au sommet de ce genre et avec l'apparition à [http://www.jobmanagement.ch/content/dienstleistungen/footer.asp Fred Perry Gen��ve] couper le souffle et la voix de la dame avant Ailyn, SIRENIENS est un must pour tout fan des goûts de Nightwish, <br><br>Mais il ya des gens sur ce site qui possèdent effectivement arbres de l'argent et ils peuvent vous donner des conseils plus impliqués. Ein FSK 12 w re vielleicht noch ein Tipp, denn ich nicht glaube, dass ein 6 j hriger dieses Spiel ganz versteht. Un signe commun de l'infidélité, c'est quand les couples commencent soudainement à se quereller souvent, habituellement démarré par le partenaire de la tricherie.<br><br>Déplacez la souris sur, faux vomi et doo [http://www.logistikleiterclub.ch/library/camera/demo/client.php Nike Talon] chien (et le plus loin possible de moi, s'il vous plaît!). Simpson. W / smart n'importe quel emploi est ok, mais dépend de votre salaire, devrait être d'environ 20 000 .. M'a fait avoir une perspective différente sur notre équipe et notre arène. <br><br>Le temps de téléchargement est une autre question importante. Si vous avoir lu des blogs de music/MP3 pendant un certain temps, il ne fait aucun [http://www.bezirksschule-gersau.ch/InfosAZ/Bilder/confuse.asp Nike Air Max 1] doute que vous avez cliqué sur l'ivrogne. Pourtant, un certain nombre de reprises, j'ai reçu une petite alerte en haut à droite qui m'a averti que la connexion au serveur a été perdue, même lorsque d'autres, les onglets non Bureau Applications fonctionné normalement.<br><br>Il parvient même à se défoncer avec sa célébrité interrogée. Aucune configuration n'est nécessaire ou requis. Vous pourriez être en mesure de rétrograder et de conserver un bouquet de fonds .. Ceci est un médicament d'ordonnance qui ralentit l'absorption du corps de sucre, donc la glycémie ne pic après un repas riche en glucides, puis plonger vers le bas par la suite.<br><br>Disponible en format numérique ou imprimé. Selon ITV, la nouvelle "Coronation Street" site Web est la première au Royaume-Uni le site de soap opera à offrir des profils de personnages en vidéo: 20 de ces profils ont lancé sur le site à ce jour, et le diffuseur en dit plus se déployer au cours de la <br><br>L'exception est l'endroit où la tour de refroidissement ou par évaporation condenseur contient pas d'eau qui est exposé à l'air et / ou leur approvisionnement en eau ou de l'électricité n'est pas connecté. Mon hygiéniste trouvé 7 4mm et deux poches de 5 mm, tous non saignement. «Dans l'ensemble, MySpace est le dernier AOL retenir quand ils étaient« trop grandes pour faire faillite? AOL Time Warner a même acheté à la hauteur de l'engouement.<ul>
==Time-domain ripple==
 
[[Image:Rectifier with reservoir.svg|thumb|left|300px|Full-wave rectifier circuit with a [[reservoir capacitor]] on the output for the purpose of smoothing ripple]]
  <li>[http://bbs.7wtx.com/home.php?mod=spacecp&ac=blog&blogid= http://bbs.7wtx.com/home.php?mod=spacecp&ac=blog&blogid=]</li>
Ripple factor (''γ'') may be defined as the ratio of the [[root mean square]] (rms) value of the ripple [[voltage]] to the [[absolute value]] of the dc component of the output voltage, usually expressed as a percentage. However, ripple voltage is also commonly expressed as the [[peak-to-peak]] value. This is largely because peak-to-peak is both easier to measure on an [[oscilloscope]] and is simpler to calculate theoretically. Filter circuits intended for the reduction of ripple are usually called [[smoothing circuit]]s.
 
 
  <li>[http://verdamilio.net/tonio/spip.php?article227/ http://verdamilio.net/tonio/spip.php?article227/]</li>
The simplest scenario in ac to dc conversion is a [[rectifier]] without any smoothing circuitry at all. The ripple voltage is very large in this situation; the peak-to-peak ripple voltage is equal to the peak ac voltage. A more common arrangement is to allow the rectifier to work into a large smoothing [[capacitor]] which acts as a reservoir. After a peak in output voltage the capacitor (C) supplies the current to the load (R) and continues to do so until the capacitor voltage has fallen to the value of the now rising next half-cycle of rectified voltage. At that point the rectifiers turn on again and deliver current to the reservoir until peak voltage is again reached. If the [[time constant]], CR, is large in comparison to the period of the ac waveform, then a reasonably accurate approximation can be made by assuming that the capacitor voltage falls linearly. A further useful assumption can be made if the ripple is small compared to the dc voltage. In this case the [[phase angle]] through which the rectifiers conduct will be small and it can be assumed that the capacitor is discharging all the way from one peak to the next with little loss of accuracy.<ref>Ryder, pp&nbsp;107–115</ref>
 
[[Image:Smoothed ripple.svg|thumb|400px|Ripple voltage from a full-wave rectifier, before and after the application of a smoothing capacitor]]
  <li>[http://verdamilio.net/tonio/spip.php?article303/ http://verdamilio.net/tonio/spip.php?article303/]</li>
With the above assumptions the peak-to-peak ripple voltage can be calculated as:<ref>Millman-Halkias, pp&nbsp;112–114</ref>
 
 
  <li>[http://enseignement-lsf.com/spip.php?article64#forum24694675 http://enseignement-lsf.com/spip.php?article64#forum24694675]</li>
For a full-wave rectifier:
 
::<math>V_\mathrm{pp} = \frac{I}{2fC}</math>
  <li>[http://verdamilio.net/tonio/spip.php?article1/ http://verdamilio.net/tonio/spip.php?article1/]</li>
 
 
For a half-wave rectification:
</ul>
::<math>V_\mathrm{pp} = \frac{I}{fC}</math>
 
where
:*<math>V_\mathrm{pp}</math> is the peak-to-peak ripple voltage
:*<math>I</math> is the current in the circuit
:*<math>f</math> is the frequency of the ac power
:*<math>C</math> is the capacitance
 
For the rms value of the ripple voltage, the calculation is more involved as the shape of the ripple waveform has a bearing on the result. Assuming a [[sawtooth wave]]form is a similar assumption to the ones above and yields the result:<ref>Ryder, p&nbsp;113</ref>
 
::<math>\gamma = \frac{1}{4\sqrt{3}fCR}</math>
 
where
:*<math>\gamma</math> is the ripple factor
:*<math>R</math> is the resistance of the load
 
Another approach to reducing ripple is to use a series [[choke (electronics)|choke]]. A choke has a filtering action and consequently produces a smoother waveform with less high-order [[harmonics]]. Against this, the dc output is close to the average input voltage as opposed to the higher voltage with the [[reservoir capacitor]] which is close to the peak input voltage. With suitable approximations, the ripple factor is given by:<ref>Ryder, pp&nbsp;115&ndash;117</ref>
 
::<math>\gamma = \frac{0.236R}{\omega L}</math>
 
where
:*<math>\omega</math> is the angular frequency <math>2 \pi f</math>
:*<math>L</math> is the [[inductance]] of the choke
 
More complex arrangements are possible; the filter can be an LC ladder rather than a simple choke or the filter and the reservoir capacitor can both be used to gain the benefits of both. The most commonly seen of these is a [[low-pass]] [[Topology (electronics)#Simple filter topologies|Π-filter]] consisting of a reservoir capacitor followed by a series choke followed by a further shunt capacitor.<ref>Ryder pp&nbsp;117&ndash;123</ref> However, use of chokes is deprecated in contemporary designs for economic reasons. A more common solution where good ripple rejection is required is to use a reservoir capacitor to reduce the ripple to something manageable and then pass through a [[voltage regulator]] circuit. The regulator circuit, as well as regulating the output, will incidentally filter out nearly all of the ripple as long as the minimum level of the ripple waveform does not go below the voltage being regulated to.<ref>Ryder pp&nbsp;353&ndash;355</ref>
 
The majority of power supplies are now [[switched-mode power supply|switched mode]]. The filtering requirements for such power supplies are much easier to meet owing to the frequency of the ripple waveform being very high. In traditional power supply designs the ripple frequency is either equal to (half-wave), or twice (full-wave) the ac line frequency. With switched mode power supplies the ripple frequency is not related to the line frequency, but is instead related to the frequency of the [[chopper (electronics)|chopper circuit]].
 
===Effects of ripple===
Ripple is undesirable in many electronic applications for a variety of reasons:
*The ripple frequency and its harmonics are within the audio band and will therefore be audible on equipment such as radio receivers, equipment for playing recordings and professional studio equipment.
*The ripple frequency is within television video bandwidth. Analogue TV receivers will exhibit a pattern of moving wavy lines if too much ripple is present.<ref>Wharton, W & Howorth, D, ''Principles of Television Reception'', p70, Pitman Publishing, 1971</ref>
*The presence of ripple can reduce the resolution of electronic test and measurement instruments. On an oscilloscope it will manifest itself as a visible pattern on screen.
*Within digital circuits, it reduces the threshold, as does any form of supply rail noise, at which logic circuits give incorrect outputs and data is corrupted.
*High-amplitude ripple currents shorten the life of [[electrolytic capacitors]].<ref>[http://www.edn.com/article/CA6588368.html Determining end-of-life, ESR, and lifetime calculations for electrolytic capacitors at higher temperatures]. EDN. Retrieved on 2013-08-18.</ref>
 
==Frequency-domain ripple==
[[Image:Tchebyscheff5.png|thumb|Ripple on a fifth order [[prototype filter|prototype]] Chebyshev filter]]
Ripple in the context of the frequency domain is referring to the periodic variation in [[insertion loss]] with frequency of a filter or some other [[two-port network]]. Not all filters exhibit ripple, some have [[monotonic function|monotonically]] increasing insertion loss with frequency such as the [[Butterworth filter]]. Common classes of filter which exhibit ripple are the [[Chebyshev filter]], [[inverse Chebyshev filter]] and the [[Elliptical filter]].<ref>Matthaei et al., pp&nbsp;85&ndash;95</ref> The ripple is not usually strictly linearly periodic as can be seen from the example plot. Other examples of networks exhibiting ripple are [[impedance matching]] networks that have been designed using [[Chebyshev polynomials]]. The ripple of these networks, unlike regular filters, will never reach 0&nbsp;dB at minimum loss if designed for optimum transmission across the [[passband]] as a whole.<ref name=Matt120>Matthaei et al., pp&nbsp;120&ndash;135</ref>
 
The amount of ripple can be traded for other parameters in the filter design. For instance, the rate of [[roll-off]] from the [[passband]] to the [[stopband]] can be increased at the expense of increasing the ripple without increasing the order of the filter (that is, the number of components has stayed the same). On the other hand, the ripple can be reduced by increasing the order of the filter while at the same time maintaining the same rate of roll-off.<ref name=Matt120/>
 
==See also==
*[[Ringing (signal)]]
 
==Notes==
{{reflist}}
 
== References ==
*Ryder, J D, ''Electronic Fundamentals & Applications'', Pitman Publishing, 1970.
*Millman-Halkias, ''Integrated Electronics'', McGraw-Hill Kogakusha, 1972.
*Matthaei, Young, Jones, ''Microwave Filters, Impedance-Matching Networks, and Coupling Structures'' McGraw-Hill 1964.
 
[[Category:Electricity]]
[[Category:Filter theory]]

Latest revision as of 15:30, 8 June 2013

Template:Two other uses

The most common meaning of ripple in electrical science is the small unwanted residual periodic variation of the direct current (dc) output of a power supply which has been derived from an alternating current (ac) source. This ripple is due to incomplete suppression of the alternating waveform within the power supply.

As well as this time-varying phenomenon, there is a frequency domain ripple that arises in some classes of filter and other signal processing networks. In this case the periodic variation is a variation in the insertion loss of the network against increasing frequency. The variation may not be strictly linearly periodic. In this meaning also, ripple is usually to be considered an unwanted effect, its existence being a compromise between the amount of ripple and other design parameters.

Time-domain ripple

Full-wave rectifier circuit with a reservoir capacitor on the output for the purpose of smoothing ripple

Ripple factor (γ) may be defined as the ratio of the root mean square (rms) value of the ripple voltage to the absolute value of the dc component of the output voltage, usually expressed as a percentage. However, ripple voltage is also commonly expressed as the peak-to-peak value. This is largely because peak-to-peak is both easier to measure on an oscilloscope and is simpler to calculate theoretically. Filter circuits intended for the reduction of ripple are usually called smoothing circuits.

The simplest scenario in ac to dc conversion is a rectifier without any smoothing circuitry at all. The ripple voltage is very large in this situation; the peak-to-peak ripple voltage is equal to the peak ac voltage. A more common arrangement is to allow the rectifier to work into a large smoothing capacitor which acts as a reservoir. After a peak in output voltage the capacitor (C) supplies the current to the load (R) and continues to do so until the capacitor voltage has fallen to the value of the now rising next half-cycle of rectified voltage. At that point the rectifiers turn on again and deliver current to the reservoir until peak voltage is again reached. If the time constant, CR, is large in comparison to the period of the ac waveform, then a reasonably accurate approximation can be made by assuming that the capacitor voltage falls linearly. A further useful assumption can be made if the ripple is small compared to the dc voltage. In this case the phase angle through which the rectifiers conduct will be small and it can be assumed that the capacitor is discharging all the way from one peak to the next with little loss of accuracy.[1]

Ripple voltage from a full-wave rectifier, before and after the application of a smoothing capacitor

With the above assumptions the peak-to-peak ripple voltage can be calculated as:[2]

For a full-wave rectifier:

For a half-wave rectification:

where

For the rms value of the ripple voltage, the calculation is more involved as the shape of the ripple waveform has a bearing on the result. Assuming a sawtooth waveform is a similar assumption to the ones above and yields the result:[3]

where

Another approach to reducing ripple is to use a series choke. A choke has a filtering action and consequently produces a smoother waveform with less high-order harmonics. Against this, the dc output is close to the average input voltage as opposed to the higher voltage with the reservoir capacitor which is close to the peak input voltage. With suitable approximations, the ripple factor is given by:[4]

where

More complex arrangements are possible; the filter can be an LC ladder rather than a simple choke or the filter and the reservoir capacitor can both be used to gain the benefits of both. The most commonly seen of these is a low-pass Π-filter consisting of a reservoir capacitor followed by a series choke followed by a further shunt capacitor.[5] However, use of chokes is deprecated in contemporary designs for economic reasons. A more common solution where good ripple rejection is required is to use a reservoir capacitor to reduce the ripple to something manageable and then pass through a voltage regulator circuit. The regulator circuit, as well as regulating the output, will incidentally filter out nearly all of the ripple as long as the minimum level of the ripple waveform does not go below the voltage being regulated to.[6]

The majority of power supplies are now switched mode. The filtering requirements for such power supplies are much easier to meet owing to the frequency of the ripple waveform being very high. In traditional power supply designs the ripple frequency is either equal to (half-wave), or twice (full-wave) the ac line frequency. With switched mode power supplies the ripple frequency is not related to the line frequency, but is instead related to the frequency of the chopper circuit.

Effects of ripple

Ripple is undesirable in many electronic applications for a variety of reasons:

  • The ripple frequency and its harmonics are within the audio band and will therefore be audible on equipment such as radio receivers, equipment for playing recordings and professional studio equipment.
  • The ripple frequency is within television video bandwidth. Analogue TV receivers will exhibit a pattern of moving wavy lines if too much ripple is present.[7]
  • The presence of ripple can reduce the resolution of electronic test and measurement instruments. On an oscilloscope it will manifest itself as a visible pattern on screen.
  • Within digital circuits, it reduces the threshold, as does any form of supply rail noise, at which logic circuits give incorrect outputs and data is corrupted.
  • High-amplitude ripple currents shorten the life of electrolytic capacitors.[8]

Frequency-domain ripple

File:Tchebyscheff5.png
Ripple on a fifth order prototype Chebyshev filter

Ripple in the context of the frequency domain is referring to the periodic variation in insertion loss with frequency of a filter or some other two-port network. Not all filters exhibit ripple, some have monotonically increasing insertion loss with frequency such as the Butterworth filter. Common classes of filter which exhibit ripple are the Chebyshev filter, inverse Chebyshev filter and the Elliptical filter.[9] The ripple is not usually strictly linearly periodic as can be seen from the example plot. Other examples of networks exhibiting ripple are impedance matching networks that have been designed using Chebyshev polynomials. The ripple of these networks, unlike regular filters, will never reach 0 dB at minimum loss if designed for optimum transmission across the passband as a whole.[10]

The amount of ripple can be traded for other parameters in the filter design. For instance, the rate of roll-off from the passband to the stopband can be increased at the expense of increasing the ripple without increasing the order of the filter (that is, the number of components has stayed the same). On the other hand, the ripple can be reduced by increasing the order of the filter while at the same time maintaining the same rate of roll-off.[10]

See also

Notes

43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.

References

  • Ryder, J D, Electronic Fundamentals & Applications, Pitman Publishing, 1970.
  • Millman-Halkias, Integrated Electronics, McGraw-Hill Kogakusha, 1972.
  • Matthaei, Young, Jones, Microwave Filters, Impedance-Matching Networks, and Coupling Structures McGraw-Hill 1964.
  1. Ryder, pp 107–115
  2. Millman-Halkias, pp 112–114
  3. Ryder, p 113
  4. Ryder, pp 115–117
  5. Ryder pp 117–123
  6. Ryder pp 353–355
  7. Wharton, W & Howorth, D, Principles of Television Reception, p70, Pitman Publishing, 1971
  8. Determining end-of-life, ESR, and lifetime calculations for electrolytic capacitors at higher temperatures. EDN. Retrieved on 2013-08-18.
  9. Matthaei et al., pp 85–95
  10. 10.0 10.1 Matthaei et al., pp 120–135