Name: three-phase power connections
Uploaded: 2024-07-08T13:19:57.000Z
Duration: 1 min 30 s
Channel: JoVE

Em sistemas trifásicos de quatro fios, três fontes de tensão conectadas em Y geram tensões de fase balanceadas.
Existem duas sequências de fases com base na ordem em que as tensões de fase atingem seus valores máximos.
A primeira, abc ou sequência positiva, envolve fasores girando no sentido anti-horário, com Vum Vbn principal, que leva Vcn. Essa sequência ocorre quando o rotor gira no sentido anti-horário.
A segunda, acb ou sequência negativa, tem fasores girando no sentido anti-horário, e Van conduz Vcn, que leva Vbn. Esta sequência corresponde à rotação do rotor no sentido horário.
Como as fontes de tensão, as três cargas podem ser conectadas em Y ou em delta.
Em configurações de carga balanceada, as impedâncias de fase são iguais em magnitude e fase.
As cargas conectadas em Y podem ser transformadas em configuração delta e vice-versa.
Com base nas configurações da fonte e carga trifásicas, existem quatro conexões possíveis.
As cargas conectadas ao delta são mais comuns do que a configuração Y devido à facilidade de adicionar e remover cargas de fases individuais sem causar desequilíbrios excessivos.
No entanto, as fontes conectadas em delta são menos comuns do que as fontes conectadas em Y devido à corrente circulante na malha delta quando as tensões trifásicas são ligeiramente desequilibradas.

tensões trifásica

Um gerador trifásico produz três tensões de magnitude igual, mas com diferença de fase de 120 graus. Essa magnitude idêntica e tensões iguais separadas por fases são conhecidas como tensões balanceadas e ajudam a minimizar a perda de energia, garantindo ao mesmo tempo um fornecimento constante de energia às cargas conectadas. Como as fontes de tensão em um sistema trifásico podem ser configuradas em formação estrela ou delta, as cargas conectadas a esses sistemas também podem ser dispostas em qualquer configuração. Essa flexibilidade na configuração da carga não é apenas uma escolha de projeto, mas uma forma de exercer controle sobre o sistema. Cargas conectadas em triângulo têm uma extremidade de cada enrolamento de fase conectada a um ponto neutro comum. Por outro lado, em cargas conectadas em delta, as extremidades dos enrolamentos de fase são conectadas em um circuito contínuo, formando um triângulo. Um sistema trifásico utiliza sistemas de quatro e três fios através de conexões estrela e delta. As tensões trifásicas na configuração estrela são:

<img alt="Equation 1" src="/files/ftp_upload/15128/15128_Equation_1.svg" style="height: 16px;">

<img alt="Equation 2" src="/files/ftp_upload/15128/15128_Equation_2.svg" style="height: 16px;">

<img alt="Equation 3" src="/files/ftp_upload/15128/15128_Equation_3.svg" style="height: 16px;">

Compreender a sequência lógica das três fases é fundamental. Quando nas sequências positiva e abc, os fasores giram no sentido anti-horário, com V_an liderando V_bn, seguido por V_cn. Esta sequência, resultante da rotação do rotor no sentido anti-horário, é uma progressão clara e ordenada.

Na sequência negativa a-c-b, os fasores giram no sentido horário, com V_an liderando V_cn e V_bn seguindo por último. Isto indica uma ordem de fase invertida em comparação com a sequência positiva, que corresponde à rotação do rotor no sentido horário.

Cada configuração, seja conectada em estrela ou em delta, permite uma condição de carga equilibrada e influencia a distribuição e o gerenciamento de tensões e correntes do circuito. Durante as configurações de carga balanceada, as impedâncias conectadas em cada fase são iguais em magnitude e fase, proporcionando energia para gerenciar seu sistema de maneira eficaz.

As cargas conectadas em estrela podem ser transformadas em configuração delta e vice-versa. Com base nos tipos de conexão da fonte e da carga, o sistema pode ser configurado de quatro maneiras principais: estrela-estrela, estrela-delta, delta-estrela e delta-delta.

Tensões Trifásica

Em sistemas trifásicos de quatro fios, três fontes de tensão conectadas em Y geram tensões de fase balanceadas.
Existem duas sequências de fases com base na ordem em ...

Education

JoVE Core

Electrical Engineering

Engenharia Elétrica

Unit 1

Unidade 1

Three-Phase Circuits

Circuitos Trifásicos

KEY TERMS AND CONCEPTS

TERMOS E CONCEITOS-CHAVE

Three-Phase Voltages

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 phase winding connects to a common neutral point. In a delta connection, the phase windings join end to end in a closed triangle.

A three-phase system may use four-wire or three-wire connections through star and delta arrangements. The phase order also matters. In the positive a-b-c sequence, the phasors rotate anticlockwise, with V an leading V bn and V cn following. This sequence matches counterclockwise rotor rotation. In the negative a-c-b sequence, the phasors rotate clockwise, with V an leading V cn and V bn last. This reversed order matches clockwise rotor rotation.

Balanced load conditions are important in both wye-connected and delta-connected systems. In a balanced load, the impedances across each phase are equal in magnitude and phase. That balance helps the circuit manage voltages and currents more effectively. Star-connected loads can also be transformed into delta form, and delta loads can be transformed into star form. Based on the source and load connections, a three-phase system can be set up as wye-wye, wye-delta, delta-wye, or delta-delta.

Three-Phase Power Connections

three-phase circuits

How Three-Phase Power Delivers Electricity

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...

generation of three-phase voltage

Three-Phase AC Generator Windings

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,...

three-phase voltages

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

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...

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...

power distribution in three-phase and single phase circuits

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

Single-Phase vs. Three-Phase Power Loss

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 three-phase power uses balanced voltages, wye and delta connections, phase sequence, and balanced loads to control voltage and current flow.

Three-Phase Power Connections | 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

Three-Phase Power Connections

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