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

In AC circuits, a current transformer converts the magnetic field around a conductor into a small AC current, typically either or at full rated current, that can be easily read by a meter.

Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a direct current component flowing through the windings.

This change in voltage is usually achieved in AC circuits using a step-up transformer.

Balanced and unbalanced circuits can be interconnected using a transformer called a balun.

When both the 2-wire and the 4-wire circuits must be balanced, double transformer hybrids are used, as shown at right.

It is a special application of an isolation transformer, and is often used to prevent ground loops or earth loops, which cause humming or buzzing in audio circuits.

# A transformer coupling two circuits may be considered a source of emf for one of the circuits, just as if it were caused by an electrical generator ; this example illustrates the origin of the term " transformer emf ".

Distribution circuits are fed from a transformer located in an electrical substation, where the voltage is reduced from the high values used for power transmission.

The two circuits interacted to form a resonant transformer.

However, only transformers whose primary purpose is to isolate circuits ( opposed to the more common transformer function of voltage conversion ), are routinely described as isolation transformers.

Without the isolation transformer, the lighting circuits on the mast would conduct radio-frequency energy to ground through the power supply.

Pentodes and Tetrodes can have their screen grid fed from a percentage of the primary voltage on the output transformer, giving efficiency and distortion that is a good compromise between triode ( or Triode-strapped ) power amplifiers circuits and conventional pentode or tetrode output circuits where the screen is fed from a relatively constant voltage source.

The primary of the transformer is connected between the high voltage line and earth, the secondary is a 3-wire single-phase system as described here, the secondary voltage being 230 / 460 V. Single phase loads are split between the two circuits.

Also, when flyback transformers fail, they frequently will also damage the horizontal output transistor that drives the flyback transformer, and sometimes even blow fuses in the low voltage power supply circuits.

A primary objective of current transformer design is to ensure that the primary and secondary circuits are efficiently coupled, so that the secondary current bears an accurate relationship to the primary current.

A high-voltage current transformer may contain several cores with multiple secondary windings for different purposes ( such as metering circuits, control, or protection ).

Though an autotransformer in appearance, like all Tesla Coils it is a resonant transformer with primary and secondary circuits tuned to the same frequency.

If the higher voltage circuit is de-energized so it can be worked on, but any one of the lower-voltage circuits connected to it via a transformer remains energized, the transformer will convert the power in the lower-voltage circuit back to the higher voltage, and the higher voltage circuit will remain energized.

Although the high switching frequency requires sophisticated components and circuits, it drastically reduces the bulk of the step down transformer, as the mass of magnetic components ( transformers and inductors ) that is required for achieving a given power level goes down rapidly as the operating ( switching ) frequency is increased.

A device that converts signals from one type to another ( for example, a light signal in photons to a DC signal in amperes ) is a transducer, a transformer, or a sensor.

A transformer is an electromagnetic device that has a primary winding and a secondary winding that transfers energy from one electrical circuit to another by inductive coupling without moving parts.

Pyrolysis of polychlorinated biphenyls ( PCB ), e. g. from burning older transformer oil, and to lower degree also of other chlorine-containing materials, can produce 2, 3, 7, 8-tetrachlorodibenzodioxin, a potent carcinogen, and other polychlorinated dibenzodioxins.

A transformer is a power converter that transfers electrical energy from one circuit to another through inductively coupled conductors — the transformer's coils.

If a load is connected to the secondary winding, current will flow in this winding, and electrical energy will be transferred from the primary circuit through the transformer to the load.

Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used in power stations, or to interconnect portions of power grids.

For example, transformers may need to be equipped with " volts per hertz " over-excitation relays to protect the transformer from overvoltage at higher than rated frequency.

Losses in the transformer arise from:

The parameters of equivalent circuit of a transformer can be calculated from the results of two transformer tests: open-circuit test and short-circuit test.

Early transformer developers soon realized that cores constructed from solid iron resulted in prohibitive eddy-current losses, and their designs mitigated this effect with cores consisting of bundles of insulated iron wires.

One common design of laminated core is made from interleaved stacks of E-shaped steel sheets capped with I-shaped pieces, leading to its name of " E-I transformer ".

Powering the filaments directly from a power transformer introduced mains-frequency ( 50 or 60 Hz ) hum into audio stages.

* Both signal and signal return may be applied to the primary of a transformer, with the signal taken from the secondary.

This transformer is designed to hold energy long enough to cover the time between switching from line power to battery power and effectively eliminates the transfer time.

Simple shielding of this type is not greatly effective against low-frequency magnetic fields, however-such as magnetic " hum " from a nearby power transformer.

* Power line, electric power transmission line fed to or from a transformer

The General Electric transformer plant dumped PCBs upstream in Hudson Falls, New York from 1947 to 1977.

These could be run from a mains transformer or, in the case of the E15R, a 12V car battery.

A bridge rectifier provides full-wave rectification from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a transformer with a center-tapped secondary winding.

For example, the energy carried from one winding of a transformer to another, or to and from a patient in an MRI scanner, in quantum terms is carried by virtual photons, not real photons .< ref name = " Hoult "> Hoult, D. I. and Bhakar, B.

* F. Ueno, T. Inoue, and I. Oota, “ Realization of a new switched-capacitor transformer with a step-up transformer ratio 2 < sup > n </ sup >– 1 using n capacitors ,” IEEE International Symposium on Circuits and Systems ( ISCAS ) 1986, pp. 805-808.