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

Les systèmes symétriques à quatre fils Y-à-Y se composent de trois sources de tension sinusoïdales symétriques connectées en Y et de charges avec le fil neutre reliant les deux nœuds neutres de la source à la charge.
L’impédance de charge de chaque phase est égale à la somme des impédances source, ligne et charge. Les impédances de la source et de la ligne sont négligées pour simplifier le système.
En considérant la séquence de phase positive, les tensions de phase déterminent les tensions à trois lignes
La loi de tension de Kirchhoff est appliquée à chaque phase, et les courants de ligne sont déterminés comme ayant des amplitudes égales et des différences de phase de 120 degrés.
Leur somme est égale à zéro, ce qui implique un courant nul dans le fil neutre.
Dans un système en Y équilibré, la puissance totale fournie à la charge triphasée est trois fois supérieure à la puissance délivrée dans chaque phase.
Pour un système Y-à-Y asymétrique avec une charge déséquilibrée, les courants de ligne sont déséquilibrés, ce qui entraîne un courant neutre non nul.
Une autre méthode d’analyse d’un système équilibré d’Y à Y consiste à considérer une phase et à analyser son circuit équivalent monophasé pour déterminer son courant de ligne. La séquence de phases donne ensuite les deux autres courants de ligne.

le circuit y-to-y

The Y-to-Y Circuit

Dans un système étoile-étoile équilibré à quatre fils, l'arrangement implique des sources et des charges de tension sinusoïdale connectées en étoile, connectées via un fil neutre qui relie les nœuds neutres de la source et de la charge. L'impédance de charge est connectée à chaque phase de la charge. La source connectée en étoile peut être connectée à la charge connectée en étoile dans des configurations à quatre ou trois fils. Un système triphasé est considéré comme équilibré lorsque la charge sur chaque phase est égale, conduisant à un flux de courant et un angle de phase uniformes sur toutes les étapes. D'un autre côté, dans un système déséquilibré, les variations de l'impédance de charge ou des tensions de source entraînent des courants de ligne inégaux.
L’analyse de la configuration du circuit étoile-étoile à quatre fils est relativement simple. Dans cette configuration, chaque impédance de la charge triphasée est connectée directement aux bornes de sa tension de phase respective à partir de la source triphasée. En supposant une séquence de phases positive et des conditions équilibrées, les tensions de phase jouent un rôle déterminant dans l'analyse du système. Ces tensions de phase influencent directement les tensions aux bornes de chaque impédance de charge.
<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_1.svg" style="text-align: center; height: 32px;">

<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_2.svg" style="text-align: center; height: 32px;">
<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_3.svg" style="text-align: center; height: 32px;">
Le courant dans le fil reliant le nœud neutre de la source au nœud neutre de la charge est :
<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_4.svg" style="text-align: center; height: 16px;">
La loi de tension de Kirchhoff, lorsqu'elle est appliquée à chaque phase d'un circuit triphasé équilibré, confirme que la somme des tensions autour de toute boucle fermée est nulle. Cela conduit à des courants de ligne d’amplitude égale mais avec des déphasages de 120 degrés entre eux. Ces courants totalisent effectivement zéro en tout point, ce qui explique pourquoi le fil neutre ne transporte aucun courant dans des conditions équilibrées.
Dans un système étoile-étoile déséquilibré, les variations de l'impédance de charge ou des tensions de source entraînent des courants de ligne inégaux. Chaque phase du système est traitée comme un circuit monophasé pour calculer son courant de ligne. Cependant, les courants pour les phases restantes nécessitent une analyse individuelle plutôt qu'une déduction uniquement basée sur la séquence des phases, car chaque phase peut être influencée de manière unique par ses conditions électriques spécifiques.

Le circuit Y-To-Y

Les systèmes Y-à-Y à quatre fils équilibrés se composent de trois sources de tension sinusoïdales équilibrées connectées en Y et de charges avec le fil neutre reliant à la fois le ...

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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

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...

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Wye Source and Delta Load Currents

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Delta-Wye Source and Load Connections

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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