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

三相4線式システムでは、3つのY接続電圧源が平衡相電圧を生成します。
位相電圧が最大値に達する順序に基づいて、2つの位相シーケンスがあります。
最初の abc または正のシーケンスでは、フェーザーが反時計回りに回転し、V が先行する Vbn で、これが Vcn につながります。このシーケンスは、ローターが反時計回りに回転するときに発生します。
2番目のacbまたは負のシーケンスは、フェーザが反時計回りに回転し、VがVCNをリードし、Vがvnをリードします。このシーケンスは、時計回りのローター回転に対応します。
電圧源と同様に、3つの負荷はY接続またはデルタ接続にすることができます。
平衡負荷構成では、位相インピーダンスの大きさと位相は等しくなります。
Y接続の負荷はデルタ構成に変換でき、その逆も可能です。
三相ソースと負荷の構成に基づいて、4つの可能な接続が存在します。
デルタ接続の負荷は、過度の不均衡を引き起こすことなく個々のフェーズから負荷を追加および削除することが容易であるため、Y構成よりも一般的です。
ただし、デルタ接続のソースは、三相電圧がわずかに不均衡な場合のデルタメッシュの循環電流により、Y接続のソースよりも一般的ではありません。

三相電圧

三相発電機は、大きさは同じですが位相差が 120 度の 3 つの電圧を生成します。この大きさが同一で位相が等しく分離された電圧はバランス電圧と呼ばれ、接続された負荷に安定したエネルギーを供給しながら電力損失を最小限に抑えるのに役立ちます。三相システムの電圧源は Y 字型またはデルタ型に構成できるため、これらのシステムに接続された負荷もどちらの構成でも配置できます。負荷構成のこの柔軟性は、設計上の選択であるだけでなく、システムを制御する方法でもあります。デルタ接続負荷では、各相巻線の一方の端が共通の中性点に接続されています。逆に、デルタ接続負荷では、相巻線の端が連続ループに接続され、三角形を形成します。三相システムでは、スター型結線とデルタ結線を介して4線式および3線式システムを使用します。 Y 字型構成の3相電圧は次のとおりです。

<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;">

3つの相の論理シーケンスを理解することが重要です。正のシーケンスとa-b-c シーケンスでは、位相器は反時計回りに回転し、Van が Vbn をリードし、その後に Vcn が続きます。ローターが反時計回りに回転することで生じるこのシーケンスは、明確で整然とした進行です。

負のシーケンス a-c-b では、位相器は時計回りに回転し、Van が Vcn をリードし、最後に Vbn が続きます。これは、時計回りのローター回転に対応する正のシーケンスと比較して、逆位相順序を示しています。

Y字型接続またはデルタ接続のいずれの構成でも、バランスの取れた負荷状態が可能になり、回路の電圧と電流の分配と管理に影響します。バランスのとれた負荷構成では、各相に接続されたインピーダンスの大きさと位相が等しくなり、システムを効果的に管理できるようになります。
スター結線された負荷はデルタ結線に変換でき、その逆も可能です。ソースと負荷の接続タイプに基づいて、システムは主に Y-Y、Y-デルタ、デルタ-Y、デルタ-デルタの 4 つの方法で構成できます。

三相4線式システムでは、3つのY接続電圧源が平衡相電圧を生成します。
の順序に基づいて2つの位相シーケンスがあります...

Education

JoVE Core

Electrical Engineering

電気工学

Unit 1

ユニット1

Three-Phase Circuits

三相回路

KEY TERMS AND CONCEPTS

主要用語および概念

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 電気工学 は、電気回路の基本概念と回路解析テクニックを網羅したアニメーションビデオシリーズです。オペアンプと回路変換および 1 次・ 2 次回路の概念を網羅しています。実験を撮影した実写動画では、設計例や現代社会での応用が含まれており、複雑な概念も分かりやすく学習いただけます。

electrical engineering

Three-Phase Power Connections

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