Polyphase coil

Polyphase coils are electromagnetic coils connected together in a polyphase system such as a generator or motor. In modern systems, the number of phases is usually three or a multiple of three. Each phase carries a sinusoidal alternating current whose phase is delayed relative to one of its neighbours and advanced relative to its other neighbour. The phase currents are separated in time evenly within each period of the alternating current. For example, in a three-phase system, the phases are separated from each other by one-third of the period.

## Contents

* 1 Coil construction
* 2 Polyphase motors and generators
* 3 History
* 4 See also
* 5 References

## Coil construction

Like all coils used in electrical machinery, polyphase coils (made from insulated conducting wire) are wound around ferromagnetic armatures with radial projections and maximum core-surface exposure to the magnetic field.

The windings are physically separated around the circumference of an electrical machine. The result of such an arrangement is a rotating magnetic field that is used to convert electrical power to rotary mechanical work, or vice versa.

## Polyphase motors and generators

Compared to single-phase motors and generators, polyphase motors are simpler, because they do not require external circuitry (using capacitors and inductors) to produce a starting torque. Polyphase machines can deliver constant power over each period of the alternating current, eliminating the pulsations found in a single-phase machine as the current passes through zero amplitude.[1]

## History

The use of polyphase coils in electrical power systems was pioneered by the engineers Nikola Tesla, Galileo Ferraris, and Michail Dolivo-Dobrovolsky.[2]

## See also

* Alternator
* Induction motor
* Single-phase generator

## References

1. ↑ "Polyphase AC Circuits Polyphase Motor Design". EETech Group, LLC. https://www.allaboutcircuits.com/TEXTBOOK/ALTERNATING-CURRENT/CHPT-10/polyphase-motor-design/.
2. ↑ "Initial Tesla Polyphase / "Three-Phase" Alternating-Current Systems and Metering Development". Institute of Electrical and Electronics Engineers (IEEE). https://ethw.org/Initial_Tesla_Polyphase_/_"Three-Phase"_Alternating-Current_Systems_and_Metering_Development#George_Westinghouse_Acquires_Tesla_Alternating-Current_Patents.

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Transformer

Types|

* Amorphous metal transformer
* Austin transformer
* Autotransformer
* Buck–boost transformer
* Capacitor voltage transformer
* Distribution transformer
* Delta-wye transformer
* Energy efficient transformer
* Flyback transformer
* Grounding transformer
* Instrument transformer
* Current transformer
* Potential transformer
* Isolation transformer
* Linear variable differential transformer
* Pad-mounted transformer
* Parametric transformer
* Planar transformers
* Rotary transformer
* Rotary variable differential transformer
* Scott-T transformer
* Solid-state transformer
* Trigger transformer
* Variable-frequency transformer
* Zigzag transformer

Coils|

* Hybrid coil
* Induction coil
* Oudin coil
* Polyphase coil
* Repeating coil
* Tesla coil
* Trembler coil

Topics|

* Agbioeletric
* Balun
* Buchholz relay
* Bushing
* Center tap
* Circle diagram
* Condition monitoring of transformers
* Copper loss
* Dissolved gas analysis
* Electrical insulation paper
* Growler
* High-leg delta
* Induction regulator
* Leakage inductance
* Magnet wire
* Metadyne
* Open-circuit test
* Polarity
* Polychlorinated biphenyl
* Quadrature booster
* Resolver
* Resonant inductive coupling
* Severity factor
* Short-circuit test
* Stacking factor
* Synchro
* Tap changer
* Toroidal inductors and transformers
* Transformer oil
* Transformer oil testing
* Transformer utilization factor
* Vector group

Manufacturers|

* ABB
* Prolec GE
* Siemens
* TBEA

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