Name: balanced wye-to-wye neutral current
Uploaded: 2024-07-08T13:19:57.000Z
Duration: 1 min 19 s
Channel: JoVE

Symmetrische Vierdraht-Y-zu-Y-Systeme bestehen aus drei symmetrisch Y-verbundenen sinusförmigen Spannungsquellen und Lasten, wobei der Neutralleiter beide Neutralleiter der Quelle mit der Last verbindet.
Die Lastimpedanz für jede Phase entspricht der Summe der Impedanzen von Quelle, Leitung und Last. Die Quellen- und Leitungsimpedanzen werden vernachlässigt, um das System zu vereinfachen.
Unter Berücksichtigung der positiven Phasenfolge bestimmen Phasenspannungen die dreizeiligen Spannungen
Das Kirchhoffsche Spannungsgesetz wird auf jede Phase angewendet, und es wird bestimmt, dass die Netzströme gleiche Größen und Phasenunterschiede von 120 Grad haben.
Ihre Summe ist gleich Null, was bedeutet, dass der Strom im Neutralleiter Null ist.
In einem symmetrischen Y-System ist die Gesamtleistung, die an die dreiphasige Last abgegeben wird, dreimal so hoch wie die in jeder Phase abgegebene Leistung.
Bei einem unsymmetrischen Y-zu-Y-System mit einer unsymmetrischen Last sind die Leitungsströme unsymmetrisch, was zu einem Neutralstrom ungleich Null führt.
Eine andere Methode zur Analyse eines symmetrischen Y-zu-Y-Systems besteht darin, eine Phase zu betrachten und ihre einphasige Ersatzschaltung zu analysieren, um ihren Netzstrom zu bestimmen. Die Phasenfolge ergibt dann die beiden anderen Linienströme.

der y-zu-y-schaltkreis

In einem symmetrischen Vierleiter-Stern-zu-Stern-System umfasst die Anordnung sternförmig verbundene sinusförmige Spannungsquellen und Lasten, die über einen Neutralleiter verbunden sind, der die Neutralknoten der Quelle und der Last verbindet. Die Lastimpedanz ist über jede Phase der Last angeschlossen. Die sternförmig verbundene Quelle kann in Vierleiter- und Dreileiteranordnungen mit der sternförmig verbundenen Last verbunden werden. Ein Dreiphasensystem gilt als symmetrisch, wenn die Last auf jeder Phase gleich ist, was zu einem gleichmäßigen Stromfluss und Phasenwinkel über alle Stufen hinweg führt. Andererseits führen in einem unsymmetrischen System Schwankungen der Lastimpedanz oder der Quellenspannungen zu ungleichen Leitungsströmen.

Die Analyse der Vierleiter-Stern-zu-Stern-Schaltkreiskonfiguration ist relativ unkompliziert. In diesem Aufbau ist jede Impedanz der Dreiphasenlast direkt über ihre jeweilige Phasenspannung von der Dreiphasenquelle angeschlossen. Unter der Annahme einer positiven Phasenfolge und symmetrischer Bedingungen sind die Phasenspannungen bei der Analyse des Systems von entscheidender Bedeutung. Diese Phasenspannungen beeinflussen direkt die Spannungen über jeder Lastimpedanz.

<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_1.svg" style="text-align: center; height: 32px;">

<img alt="Equation 2" src="/files/ftp_upload/15129/15129_Equation_2.svg" style="text-align: center; height: 32px;">

<img alt="Equation 3" src="/files/ftp_upload/15129/15129_Equation_3.svg" style="text-align: center; height: 32px;">

Der Strom im Kabel, das den Neutralknoten der Quelle mit dem Neutralknoten der Last verbindet, ist:

<img alt="Equation 4" src="/files/ftp_upload/15129/15129_Equation_4.svg" style="text-align: center; height: 16px;">

Kirchhoffs Spannungsgesetz bestätigt, wenn es auf jede Phase eines symmetrischen Dreiphasenstromkreises angewendet wird, dass die Summe der Spannungen um jeden geschlossenen Stromkreis Null ist. Dies führt zu Leitungsströmen gleicher Stärke, aber mit 120-Grad-Phasenverschiebungen zwischen ihnen. Diese Ströme summieren sich an jedem Punkt effektiv zu Null, was erklärt, warum der Neutralleiter unter symmetrischen Bedingungen keinen Strom führt.

In einem unsymmetrischen Stern-zu-Stern-System führen Schwankungen in der Lastimpedanz oder den Quellenspannungen zu ungleichen Leitungsströmen. Jede Phase im System wird als einphasiger Stromkreis behandelt, um ihren Leitungsstrom zu berechnen. Die Ströme für die übrigen Phasen müssen jedoch einzeln analysiert und nicht ausschließlich aus der Phasenfolge abgeleitet werden, da jede Phase durch ihre spezifischen elektrischen Bedingungen individuell beeinflusst werden kann.

Der Y-zu-Y-Schaltkreis

Symmetrische Vierleiter-Y-zu-Y-Systeme bestehen aus drei symmetrisch Y-verbundenen sinusförmigen Spannungsquellen und -lasten, wobei der Neutralleiter sowohl die ...

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The Y-to-Y Circuit

balanced wye-to-wye neutral current

A balanced wye-to-wye circuit uses three wye-connected sinusoidal voltage sources and three wye-connected loads. A neutral wire links the neutral node of the source to the neutral node of the load. The load impedance is connected across each phase of the load.

The source and load can be connected in either a four-wire or a three-wire arrangement. A three-phase system is balanced when each phase has the same load. In that case, the current flow and phase angle are uniform across the system. If the load impedance or source voltages differ, the system becomes unbalanced and the line currents are no longer equal.

The four-wire wye-wye circuit is relatively easy to analyze. Each load impedance is connected directly across its own phase voltage from the three-phase source. With a positive phase sequence and balanced conditions, the phase voltages are the key to finding the voltages across each load impedance.

Kirchhoff's Voltage Law applies to each phase of a balanced three-phase circuit. The sum of the voltages around any closed loop is zero. This produces line currents with equal magnitude and 120-degree phase shifts. Their sum is zero at any point, so the neutral wire carries no current when the system is balanced.

An unbalanced wye-to-wye system must be treated differently. Changes in load impedance or source voltages create unequal line currents. Each phase is handled as a single-phase circuit to find its line current. The other phases must be analyzed on their own, since each one may be affected by its specific electrical conditions rather than by phase sequence alone.

Balanced Wye-to-Wye Neutral Current

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the y-to-y circuit

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A balanced delta-wye circuit connects a delta-connected source to a wye-connected load. In this setup, the phase voltage of the delta source equals the line voltage of the wye load. The source also sets the line currents that flow into the load. For a balanced system, the phase difference between currents makes it possible to find one line current from the other by using the positive sequence of phases. In the wye-connected load, each phase current equals the line current from the delta source.

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key terms and concepts

Learn how balanced and unbalanced wye-to-wye circuits work, why the neutral wire carries no current in balanced conditions, and how line currents are analyzed.

Balanced Wye-to-Wye Neutral Current | JoVE K12

JoVE Core Electrical Engineering offers easy-to-understand animated videos that cover fundamental concepts of electric circuits along with circuit analysis techniques. It incorporates first-order and second-order circuits using operational amplifiers and circuit transformation concepts. The inclusion of practical design examples and real-world applications through scientist-in-action videos adds significant educational value, making complex concepts accessible.

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Balanced Wye-to-Wye Neutral Current

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