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

I sistemi Y-to-Y bilanciati a quattro fili sono costituiti da tre sorgenti di tensione sinusoidali bilanciate collegate a Y e carichi con il filo neutro che collega entrambi i nodi neutri della sorgente con il carico.
L'impedenza di carico per ciascuna fase è uguale alla somma delle impedenze di sorgente, linea e carico. Le impedenze della sorgente e della linea sono trascurate per semplificare il sistema.
Considerando la sequenza di fase positiva, le tensioni di fase determinano le tensioni a tre linee
La legge della tensione di Kirchhoff viene applicata a ciascuna fase e le correnti di linea sono determinate per avere grandezze uguali e differenze di fase di 120 gradi.
La loro somma è uguale a zero, il che implica una corrente zero nel filo neutro.
In un sistema a Y bilanciato, la potenza totale erogata al carico trifase è tre volte la potenza erogata in ciascuna fase.
Per un sistema Y-Y sbilanciato con un carico sbilanciato, le correnti di linea sono sbilanciate, risultando in una corrente neutra diversa da zero.
Un altro metodo per analizzare un sistema bilanciato Y-Y consiste nel considerare una fase e analizzare il suo circuito equivalente monofase per determinare la sua corrente di linea. La sequenza di fase produce quindi le altre due correnti di linea.

il circuito stella-stella

In un sistema bilanciato stella-stella a quattro fili, la disposizione prevede sorgenti e carichi di tensione sinusoidali collegati a stella, collegati tramite un filo neutro che collega i nodi neutri della sorgente e del carico. L'impedenza di carico è collegata a ciascuna fase del carico. La sorgente collegata a stella può essere collegata al carico collegato a stella in disposizioni a quattro e tre fili. Un sistema trifase è considerato equilibrato quando il carico su ciascuna fase è uguale, portando a un flusso di corrente e un angolo di fase uniformi in tutti gli stadi. D'altra parte, in un sistema sbilanciato, le variazioni nell'impedenza di carico o nelle tensioni di sorgente determinano correnti di linea disuguali.


L'analisi della configurazione del circuito stella-stella a quattro fili è relativamente semplice. In questa configurazione, ciascuna impedenza del carico trifase è collegata direttamente attraverso la rispettiva tensione di fase dalla sorgente trifase. Supponendo una sequenza di fase positiva e condizioni equilibrate, le tensioni di fase sono determinanti nell'analisi del sistema. Queste tensioni di fase influenzano direttamente le tensioni attraverso ciascuna impedenza di carico.


<img alt="Equation 1" src="/files/ftp_upload/15129/15129_Equation_1.svg" style="height: 32px;">
<img alt="Equation 2" src="/files/ftp_upload/15129/15129_Equation_2.svg" style="height: 32px;">
<img alt="Equation 3" src="/files/ftp_upload/15129/15129_Equation_3.svg" style="height: 32px;">

La corrente nel filo che collega il nodo neutro della sorgente al nodo neutro del carico è:


<img alt="Equation 4" src="/files/ftp_upload/15129/15129_Equation_4.svg" style="height: 16px;">

La legge sulla tensione di Kirchhoff, applicata a ciascuna fase di un circuito trifase bilanciato, conferma che la somma delle tensioni attorno a qualsiasi anello chiuso è zero. Ciò porta a correnti di linea di uguale entità ma con sfasamenti di 120 gradi tra di loro. Queste correnti effettivamente si sommano a zero in qualsiasi punto, il che giustifica il motivo per cui il filo neutro non trasporta corrente in condizioni equilibrate.


In un sistema stella-stella sbilanciato, le variazioni nell'impedenza di carico o nelle tensioni della sorgente determinano correnti di linea disuguali. Ciascuna fase del sistema viene trattata come un circuito monofase per calcolare la corrente di linea. Tuttavia, le correnti per le restanti fasi richiedono un'analisi individuale anziché una deduzione basata esclusivamente sulla sequenza delle fasi, poiché ciascuna fase può essere influenzata in modo univoco dalle sue condizioni elettriche specifiche.

Il Circuito Stella-Stella

I sistemi Y-to-Y bilanciati a quattro fili sono costituiti da tre sorgenti di tensione sinusoidali bilanciate collegate a Y e carichi con il filo neutro che collega sia il filo ...

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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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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.

electrical engineering

Balanced Wye-to-Wye Neutral Current

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