Scott-T transformer

Standard Scott Connection 3 φ to 2 φ
Scott Connection 3 φ to 3 φ

Type of circuit used to produce two-phase electric power (2 φ, 90 degree phase rotation) from a three-phase (3 φ, 120 degree phase rotation) source, or vice versa.

- Scott-T transformer
Standard Scott Connection 3 φ to 2 φ

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Three-phase transformer with four wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases

Three-phase electric power

Common type of alternating current used in electricity generation, transmission, and distribution.

Common type of alternating current used in electricity generation, transmission, and distribution.

Three-phase transformer with four wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases
The first AC motor developed by Italian physicist Galileo Ferraris. This was a two-phase motor and required four wires.
Normalized waveforms of the instantaneous voltages in a three-phase system in one cycle with time increasing to the right. The phase order is 1‑2‑3. This cycle repeats with the frequency of the power system. Ideally, each phase's voltage, current, and power is offset from the others’ by 120°.
Three-phase electric power transmission lines
Three-phase transformer (Békéscsaba, Hungary): on the left are the primary wires and on the right are the secondary wires
Animation of three-phase current
Wye (Y) and delta (Δ) circuits
A delta-wye configuration across a transformer core (note that a practical transformer would usually have a different number of turns on each side).
A transformer for a "high-leg delta" system used for mixed single-phase and three-phase loads on the same distribution system. Three-phase loads such as motors connect to L1, L2, and L3. Single-phase loads would be connected between L1 or L2 and neutral, or between L1 and L2. The L3 phase is 1.73 times the L1 or L2 voltage to neutral so this leg is not used for single-phase loads.
Three-phase AC generator connected as a wye or star source to a wye or star connected load
Three-phase AC generator connected as a wye source to a delta-connected load
Three-phase electric machine with rotating magnetic fields
Three phase plug used in the past on electric stoves in Germany

It also makes it possible to produce a rotating magnetic field in an electric motor and generate other phase arrangements using transformers (for instance, a two phase system using a Scott-T transformer).

Charles F. Scott (engineer)

Charles Felton Scott (September 19, 1864 in Athens, Ohio – December 17, 1944) was an electrical engineer, professor at Yale University and known for his invention of the Scott-T transformer in the 1890s.

Pole-mounted distribution transformer with center-tapped secondary winding used to provide "split-phase" power for residential and light commercial service, which in North America is typically rated 120/240 V.

Transformer

Passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits.

Passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits.

Pole-mounted distribution transformer with center-tapped secondary winding used to provide "split-phase" power for residential and light commercial service, which in North America is typically rated 120/240 V.
Ideal transformer connected with source VP on primary and load impedance ZL on secondary, where 0 < ZL < ∞.
Ideal transformer and induction law
Leakage flux of a transformer
Real transformer equivalent circuit
Instrument transformer, with polarity dot and X1 markings on low-voltage ("LV") side terminal
Power transformer overexcitation condition caused by decreased frequency; flux (green), iron core's magnetic characteristics (red) and magnetizing current (blue).
Laminated core transformer showing edge of laminations at top of photo
Interleaved E-I transformer laminations showing air gap and flux paths
Laminating the core greatly reduces eddy-current losses
Small toroidal core transformer
Windings are usually arranged concentrically to minimize flux leakage.
Cut view through transformer windings. Legend: White: Air, liquid or other insulating medium Green spiral: Grain oriented silicon steel Black: Primary winding Red: Secondary winding
Cutaway view of liquid-immersed transformer. The conservator (reservoir) at top provides liquid-to-atmosphere isolation as coolant level and temperature changes. The walls and fins provide required heat dissipation.
Substation transformer undergoing testing.
An electrical substation in Melbourne, Australia showing three of five 220 kV – 66 kV transformers, each with a capacity of 150 MVA
Camouflaged transformer in Langley City
Transformer at the Limestone Generating Station in Manitoba, Canada
Schematic of a large oil-filled power transformer 1. Tank 2. Lid 3. Conservator tank 4. Oil level indicator 5. Buchholz relay for detecting gas bubbles after an internal fault 6. Piping 7. Tap changer 8. Drive motor for tap changer 9. Drive shaft for tap changer 10. High voltage (HV) bushing 11. High voltage bushing current transformers 12. Low voltage (LV) bushing 13. Low voltage current transformers 14. Bushing voltage-transformer for metering 15. Core 16. Yoke of the core 17. Limbs connect the yokes and hold them up 18. Coils 19. Internal wiring between coils and tapchanger 20. Oil release valve 21. Vacuum valve
Faraday's experiment with induction between coils of wire
Induction coil, 1900, Bremerhaven, Germany
Faraday's ring transformer
Shell form transformer. Sketch used by Uppenborn to describe ZBD engineers' 1885 patents and earliest articles.
Core form, front; shell form, back. Earliest specimens of ZBD-designed high-efficiency constant-potential transformers manufactured at the Ganz factory in 1885.
The ZBD team consisted of Károly Zipernowsky, Ottó Bláthy and Miksa Déri
Stanley's 1886 design for adjustable gap open-core induction coils
"E" shaped plates for transformer cores developed by Westinghouse

General winding configuration: By IEC vector group, two-winding combinations of the phase designations delta, wye or star, and zigzag; autotransformer, Scott-T

A simplified diagram of a two-phase alternator

Two-phase electric power

Early 20th-century polyphase alternating current electric power distribution system.

Early 20th-century polyphase alternating current electric power distribution system.

A simplified diagram of a two-phase alternator

Two-phase power can be derived from a three-phase source using two transformers in a Scott connection: One transformer primary is connected across two phases of the supply.

Topology of blocking mode cycloconverter

Tap converter

Variation on the cycloconverter, invented in 1981 by New York City electrical engineer Melvin Sandler and significantly functionally enhanced in 1982 through 1984 by graduate students Mariusz Wrzesniewski, Bruce David Wilner, and Eddie Fung.

Variation on the cycloconverter, invented in 1981 by New York City electrical engineer Melvin Sandler and significantly functionally enhanced in 1982 through 1984 by graduate students Mariusz Wrzesniewski, Bruce David Wilner, and Eddie Fung.

Topology of blocking mode cycloconverter

By employing a Scott transformer input connection, in order to provide a quadrature phase, an even smoother output waveform can be obtained.

Packaging of Eimac 8974

8974

Power tetrode designed for megawatt power levels in industrial and broadcast applications.

Power tetrode designed for megawatt power levels in industrial and broadcast applications.

Packaging of Eimac 8974

The two filaments may be excited in quadrature to reduce hum contributed by an AC power source.

Schematic of a synchro transducer. The complete circle represents the rotor. The solid bars represent the cores of the windings next to them. Power to the rotor is connected by slip rings and brushes, represented by the circles at the ends of the rotor winding. As shown, the rotor induces equal voltages in the 120° and 240° windings, and no voltage in the 0° winding. [Vex] does not necessarily need to be connected to the common lead of the stator star windings.

Synchro

A synchro (also known as selsyn and by other brand names) is, in effect, a transformer whose primary-to-secondary coupling may be varied by physically changing the relative orientation of the two windings.

A synchro (also known as selsyn and by other brand names) is, in effect, a transformer whose primary-to-secondary coupling may be varied by physically changing the relative orientation of the two windings.

Schematic of a synchro transducer. The complete circle represents the rotor. The solid bars represent the cores of the windings next to them. Power to the rotor is connected by slip rings and brushes, represented by the circles at the ends of the rotor winding. As shown, the rotor induces equal voltages in the 120° and 240° windings, and no voltage in the 0° winding. [Vex] does not necessarily need to be connected to the common lead of the stator star windings.
Simple two-synchro system.
A picture of a synchro transmitter
View onto the connection description of a synchro transmitter

A special T-connected transformer arrangement invented by Scott ("Scott T") interfaces between resolver and synchro data formats; it was invented to interconnect two-phase AC power with three-phase power, but can also be used for precision applications.

One voltage cycle of a three-phase system, labeled 0 to 360° (2π radians) along the time axis. The plotted line represents the variation of instantaneous voltage (or current) with respect to time. This cycle repeats with a frequency that depends on the power system.

Mathematics of three-phase electric power

In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating voltages that are offset in time by one-third of the period.

In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating voltages that are offset in time by one-third of the period.

One voltage cycle of a three-phase system, labeled 0 to 360° (2π radians) along the time axis. The plotted line represents the variation of instantaneous voltage (or current) with respect to time. This cycle repeats with a frequency that depends on the power system.
Elementary six-wire three-phase alternator, with each phase using a separate pair of transmission wires.
Elementary three-wire three-phase alternator, showing how the phases can share only three transmission wires.
Each phase of a three-phase transformer has its own pair of windings, with a shared core.

This Scott T connection produces a true two-phase system with 90° time difference between the phases.

Index of electrical engineering articles

Alphabetical list of articles pertaining specifically to electrical and electronics engineering.

Alphabetical list of articles pertaining specifically to electrical and electronics engineering.

Scott-T transformer –