Two-phase electrical power was an early 20th-century polyphase alternating current electric power distribution system. Two circuits were used, with voltage phases differing by one-quarter of a cycle, 90°. Usually circuits used four wires, two for each phase. Less frequently, three wires were used, with a common wire with a larger-diameter conductor. Some early two-phase generators had two complete rotor and field assemblies, with windings physically offset to provide two-phase power. The generators at Niagara Falls installed in 1895 were the largest generators in the world at that time, and were two-phase machines. Three-phase systems eventually replaced the original two-phase power systems for power transmission and utilization. Active two-phase distribution systems remain in Center City Philadelphia, where many commercial buildings are permanently wired for two-phase, and in Hartford, Connecticut. The advantage of two-phase electrical power over single-phase was that it allowed for simple, self-starting electric motors. In the early days of electrical engineering, it was easier to analyze and design two-phase systems where the phases were completely separated. It was not until the invention of the method of symmetrical components in 1918 that polyphase power systems had a convenient mathematical tool for describing unbalanced load cases. The revolving magnetic field produced with a two-phase system allowed electric motors to provide torque from zero motor speed, which was not possible with a single-phase induction motor (without an additional starting means). Induction motors designed for two-phase operation use a similar winding configuration as capacitor start single-phase motors. However, in a two-phase induction motor, the impedances of the two windings are identical. Two-phase circuits also have the advantage of constant combined power into an ideal load, whereas power in a single-phase circuit pulsates at twice the line frequency due to the zero crossings of voltage and current.

About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Related courses (14)
MICRO-101: Electrotechnics II
En régime alternatif, les différents types de puissance sont introduites. Les systèmes alternatifs triphasés et leurs charges sont traités. Finalement, le cours traite des régimes transitoires, base d
EE-470: Power systems dynamics
This course focuses on the dynamic behavior of a power system. It presents the basic definitions, concepts and models for angular stability analysis with reference to transient stability, steady state
EE-106: Electrical engineering science & technology
Ce cours introduit les lois fondamentales de l'électricité et les méthodes permettant d'analyser des circuits électriques linéaires, composés de résistances, condensateurs et inductances. On commencer
Show more
Related lectures (42)
Circuits in Sinusoidal Mode
Explores the fear of missing out on social media and the behavior of circuits in sinusoidal mode.
Rotating Field and Winding, Rotating Field SpeedMOOC: Conversion electromécanique II
Covers pole pairs, rotating field speed calculation, and direction of rotation.
Symmetrical Three-Phase Systems
Explains the generation of symmetrical three-phase systems and the calculation of active, reactive, and apparent power.
Show more
Related publications (118)

Simulations of primary and secondary ice production during an Arctic mixed-phase cloud case from the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) campaign

Georgia Sotiropoulou, Paraskevi Georgakaki

The representation of Arctic clouds and their phase distributions, i.e., the amount of ice and supercooled water, influences predictions of future Arctic warming. Therefore, it is essential that cloud phase is correctly captured by models in order to accur ...
Copernicus Gesellschaft Mbh2024

Advanced Frameworks to Aggregate and Unlock the Power Flexibility of Distributed Energy Resources Located in Active Distribution Networks

Mohsen Kalantar Neyestanaki

Environmental concerns are leading to a fast transition in electric power systems towards replacing fossil fuel and nuclear generation with renewable generation. This transition has two significant implications for electric power systems:1-The capacity of ...
EPFL2022

Time-Synchronization Attack Detection in Unbalanced Three-Phase Systems

Jean-Yves Le Boudec, Mario Paolone, Marguerite Marie Nathalie Delcourt, Gyorgy Miklos Dan

Phasor measurement units (PMU) rely on an accurate time-synchronization to phase-align the phasors and timestamp the voltage and current phasor measurements. Among the symmetrical components computed from the phasors in three-phase systems, the standard pr ...
2021
Show more
Related concepts (6)
Polyphase system
A polyphase system is a means of distributing alternating-current (AC) electrical power where the power transfer is constant during each electrical cycle. AC phase refers to the phase offset value (in degrees) between AC in multiple conducting wires; phases may also refer to the corresponding terminals and conductors, as in color codes. Polyphase systems have three or more energized electrical conductors carrying alternating currents with a defined phase between the voltage waves in each conductor; for three-phase voltage, the phase angle is 120° or 2π/3 radians (although early systems used 4 wire two-phase).
Single-phase electric power
In electrical engineering, single-phase electric power (abbreviated 1φ) is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a rotating magnetic field; single-phase motors need additional circuits for starting (capacitor start motor), and such motors are uncommon above 10 kW in rating.
Induction motor
An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor can therefore be made without electrical connections to the rotor. An induction motor's rotor can be either wound type or squirrel-cage type. Three-phase squirrel-cage induction motors are widely used as industrial drives because they are self-starting, reliable, and economical.
Show more
Related MOOCs (2)
Electrical Engineering II
Découvrez les systèmes alternatifs triphasés et leurs charges associées ainsi que les régimes transitoires, base des alimentations à découpage.
Electrical Engineering II
Découvrez les systèmes alternatifs triphasés et leurs charges associées ainsi que les régimes transitoires, base des alimentations à découpage.

Graph Chatbot

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.