Name: wye source and delta load currents
Uploaded: 2024-07-08T13:19:57.000Z
Duration: 1 min 19 s
Channel: JoVE

Nelle reti elettriche, i circuiti bilanciati da Y a Delta sono dotati di sorgenti di tensione collegate a Y e carichi collegati a triangolo, in genere senza una linea neutra.
Assumendo una sequenza di fase positiva, le tensioni di fase sono espresse per stimare le tensioni di linea.
Queste tensioni di linea sono uguali alle tensioni attraverso le impedenze di carico e facilitano il calcolo delle correnti di fase, che hanno grandezze simili e sono sfasate di 120 gradi.
L'applicazione della legge di corrente di Kirchhoff ai nodi dei carichi connessi a delta rivela la relazione tra la linea e le correnti di fase.
Le grandezze delle correnti di linea calcolate sono la radice quadrata di tre volte le grandezze delle correnti di fase corrispondenti e le correnti di linea sono in ritardo rispetto alle correnti di fase di 30 gradi.
Un altro modo per analizzare il sistema Y-Delta è convertire i carichi connessi a delta nella corrispondente configurazione Y.
Il sistema Y-Y bilanciato risultante può quindi essere analizzato considerando il suo circuito equivalente monofase e determinando le correnti di linea.
Le grandezze e gli angoli di fase delle correnti di fase sono calcolati dalle correnti di linea corrispondenti utilizzando appropriate trasformazioni da Delta a Y.

il circuito stella-triengolo

Un circuito bilanciato stella-triangolo comprende sorgenti di tensione bilanciate collegate a stella e carichi collegati a triangolo senza connessione di linea neutra.


Il passo iniziale nell'analisi di un circuito stella-triangolo è assumere una sequenza di fase positiva. Queste tensioni di fase vengono quindi utilizzate per calcolare le tensioni di linea che si verificano direttamente attraverso le impedenze di carico collegate a triangolo. V_an, V_bn e V_cn sono le tensioni di fase a stella e V_ab, V_bc e V_ca sono le tensioni di linea per un circuito a triangolo. La relazione tra le tensioni di linea per un circuito stella-triangolo può essere calcolata come:


<img alt="Equation 1" src="/files/ftp_upload/15130/15130_Equation_1.svg" style="height: 13px;">
<img alt="Equation 2" src="/files/ftp_upload/15130/15130_Equation_2.svg" style="height: 13px;">
<img alt="Equation 3" src="/files/ftp_upload/15130/15130_Equation_3.svg" style="height: 13px;">

Queste tensioni attraverso le impedenze di carico vengono successivamente utilizzate per calcolare le correnti di fase utilizzando la legge di Ohm. A causa della natura bilanciata del circuito, queste correnti di fase hanno grandezze identiche ma sono separate in fase di 120 gradi.


La legge della corrente di Kirchhoff (KCL) viene applicata ai nodi dei carichi collegati a triangolo per ricavare la relazione tra le correnti di linea e di fase.

In un sistema stella-triangolo bilanciato, l'entità delle correnti di linea è correlata all'ampiezza delle correnti di fase per un fattore della radice quadrata di 3. Le correnti di linea ritardano di 30 gradi rispetto alle correnti di fase corrispondenti nella configurazione delta.


Un metodo alternativo per analizzare il circuito stella-triangolo consiste nel trasformare i carichi collegati a triangolo in una configurazione stella equivalente. Ciò convertirà il circuito in un sistema stella-stella bilanciato, che può essere semplificato in circuiti equivalenti monofase per l'analisi. In questo modo è possibile stimare le correnti di fase dalle corrispondenti correnti di linea, considerando lo sfasamento introdotto dalla trasformazione.


Questa comprensione dettagliata delle correnti di fase e di linea e della relazione tra sorgenti collegate a stella e carichi collegati a triangolo è essenziale per progettare e gestire un sistema elettrico efficiente.

il circuito Stella-Triengolo

Nelle reti elettriche, i circuiti bilanciati da Y a Delta sono dotati di sorgenti di tensione collegate a Y e carichi collegati a triangolo, in genere senza una linea neutra.
...

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Electrical Engineering

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Unit 1

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Three-Phase Circuits

Circuiti Trifase

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TERMINI E CONCETTI CHIAVE

The Y-to-Delta Circuit

wye source and delta load currents

A balanced wye source and delta load form a common three-phase circuit with no neutral line connection. The source is Y-connected, and the load is delta-connected. To analyze the circuit, the first step is to assume a positive phase sequence. These phase voltages are then used to find the line voltages that appear across the delta load impedances.

In the wye source, the phase voltages are V an, V bn, and V cn. In the delta load, the line voltages are V ab, V bc, and V ca. These line voltages are the voltages across the load impedances. They are used with Ohm's law to calculate the phase currents in the delta branches.

Because the circuit is balanced, the phase currents all have the same magnitude. They are also separated by 120 degrees. Kirchhoff's Current Law, or KCL, is then applied at the nodes of the delta load to connect line currents and phase currents. In a balanced wye-to-delta system, the line current magnitude is related to the phase current magnitude by a factor of square root of 3.

The line currents also lag their matching phase currents by 30 degrees in the delta configuration. Another way to study the circuit is to transform the delta-connected loads into an equivalent wye. This changes the problem into a balanced wye-to-wye system. That form can be reduced to single-phase equivalent circuits, which makes the current analysis simpler.

Wye Source and Delta Load Currents

three-phase circuits

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Three-phase power is a major part of AC power distribution, especially where steady and efficient electricity delivery is needed. AC systems are grouped into single-phase, two-phase, and three-phase systems. These categories help describe how power moves from the source to the load. Single-phase circuits are common in homes. They usually use a two-wire system that connects one AC source to loads. These circuits can supply everyday appliances such as lamps, televisions, and microwaves at 120 V...

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A three-phase AC generator uses rotating magnet windings and a stationary stator to make three-phase voltage. The rotor carries a magnet that spins inside the stator. The stator holds the three-phase winding, and mutual induction creates the voltage. The stator windings are spread evenly around the inside of the stator. They are placed 120 electrical degrees apart. These windings consist of three separate coils, or groups of coils, called phases. The phases can be connected in a Y, or star,...

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Three-Phase Power Connections

Three-phase power connections use balanced voltages that are equal in magnitude and separated by 120 degrees. A three-phase generator produces these voltages, and the balance helps reduce power loss while keeping energy delivery steady to connected loads. Three-phase sources can be arranged in either wye or delta form. The loads connected to the system can also use wye or delta. This flexibility gives control over how the system is designed and managed. In a wye connection, one end of each...

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 y-to-delta circuit

A balanced wye source and delta load form a common three-phase circuit with no neutral line connection. The source is Y-connected, and the load is delta-connected. To analyze the circuit, the first step is to assume a positive phase sequence. These phase voltages are then used to find the line voltages that appear across the delta load impedances. In the wye source, the phase voltages are V an, V bn, and V cn. In the delta load, the line voltages are V ab, V bc, and V ca. These line voltages...

the delta-to-delta circuit

Balanced Delta-Delta Power Circuit

A balanced delta-delta power circuit uses a delta-connected source and a delta-connected load. The two deltas form a closed loop that creates three separate phases. In this setup, the phase voltages are the same as the line voltages. If the source is in positive sequence, the phase voltages can be written directly, and no neutral wire is needed. The delta-connected load current is found by dividing the phase voltage by the impedance of each phase. For line current, Kirchhoff’s Current Law...

the delta-to-y circuit

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.

power in a three-phase circuit

Balanced Three-Phase Power Calculation

Balanced three-phase power calculation depends on the wye and delta connections used in the circuit. A wye, or star, configuration can use three wires or four wires. A delta configuration connects the components in a closed loop. These connection types change how voltages and currents are arranged, but both are used in three-phase systems. In a balanced three-phase system, instantaneous power is the power at one exact moment. Even though the power in each phase changes over time, the total...

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power-distribution-in-three-phase-and-single-phase-circuits

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Single-phase and three-phase circuits distribute electrical power in different ways. Single-phase power is common in homes, while balanced three-phase power is widely used in industrial settings with heavy machinery. Both systems deliver energy, but their current flow and wire needs are not the same. A single-phase circuit usually uses a two-wire system. The current depends on the power absorbed by the load and the line voltage. Because wire loss from resistance follows the square of the...

line loss

Reducing Power Loss in Three-Phase Lines

Three-phase power lines can lose energy as electricity travels from the source to the load. This line loss affects how efficiently power reaches the load. In balanced three-phase circuits, the symmetry makes the analysis easier because one phase can represent the whole system. The source-load connection can use wye, also called star, or delta configurations. These setups change the relationship between line voltage, phase voltage, line current, and phase current. A per-phase equivalent circuit...

reducing line loss

Cutting Heat Loss in Three-Phase Lines

Three-phase power systems can lose energy as heat in transmission lines because the wires have resistance. This line loss becomes important when electricity travels over a distance. A common solution is to use transformers to change the voltage and current in the system. The setup uses two three-phase transformers. A step-up transformer is placed at the source, and a step-down transformer is placed at the load. Raising the voltage at the source lowers the current in the transmission lines, and...

key terms and concepts

Learn how balanced wye sources and delta loads work, including phase voltages, line voltages, KCL, and the 30-degree shift in line currents.

Wye Source and Delta Load Currents | 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

Wye Source and Delta Load Currents

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