transformer

transformeriron-core transformer

trans·form·er

T0317800 (trăns-fôr′mər)n.1. One that transforms: a transformer of recruits into soldiers.2. A device used to transfer electric energy from one circuit to another, especially a pair of multiply wound, inductively coupled wire coils that effect such a transfer with a change in voltage, current, phase, or other electric characteristic.

transformer

(trænsˈfɔːmə) n1. (Electronics) a device that transfers an alternating current from one circuit to one or more other circuits, usually with an increase (step-up transformer) or decrease (step-down transformer) of voltage. The input current is fed to a primary winding, the output being taken from a secondary winding or windings inductively linked to the primary2. a person or thing that transforms

trans•form•er

(trænsˈfɔr mər)

n. 1. a person or thing that transforms. 2. a device that uses electromagnetic induction to transfer electrical energy from one circuit to another, usu. with a change in voltage and current. [1595–1605]

transformerThe increase or decrease in voltage is directly related to the number of turns of the wire. In the top transformer, the outgoing voltage is doubled because the secondary coil has twice as many turns as the first. In the bottom transformer, the voltage is halved.

trans·form·er

(trăns-fôr′mər) A device used to change the voltage of an alternating current in one circuit to a different voltage in a second circuit. Transformers consist of a frame-like iron core that has a wire wound around each end. As a current enters the transformer through one of the coils, the magnetic field it produces causes the other coil to pick up the current. ♦ If there are more turns on the second coil than on the first coil, the outgoing current will have a higher voltage than the incoming current. This is called a step-up transformer. ♦ If there are fewer turns on the second coil than on the first, the outgoing current will have a lower voltage. This is called a step-down transformer.

transformer

A device transferring an alternating current from one circuit to another.

Thesaurus

Noun

transformer - an electrical device by which alternating current of one voltage is changed to another voltagecoil - a transformer that supplies high voltage to spark plugs in a gasoline engineelectrical device - a device that produces or is powered by electricityinduction coil - a coil for producing a high voltage from a low-voltage sourceprimary coil, primary winding, primary - coil forming the part of an electrical circuit such that changing current in it induces a current in a neighboring circuit; "current through the primary coil induces current in the secondary coil"secondary coil, secondary winding, secondary - coil such that current is induced in it by passing a current through the primary coilstep-down transformer - a transformer that reduces voltagestep-up transformer - a transformer that increases voltageTesla coil - a step-up transformer with an air core; used to produce high voltages at high frequenciesvoltage regulator - a transformer whose voltage ratio of transformation can be adjusted

Translations

变压器

transform

(trӕnsˈfoːm) verb to change the appearance or nature of completely. He transformed the old kitchen into a beautiful sitting-room; His marriage has transformed him. 改造，改变 ˌtransforˈmation noun1. the act of transforming or process of being transformed. the transformation of water into ice. 改造，转化 2. a change. The event caused a transformation in her character.变化transˈformer noun an apparatus for changing electrical energy from one voltage to another. 变压器

transformer

transformer,

electrical device used to transfer an alternating current or voltage from one electric circuit to another by means of electromagnetic inductioninduction,
in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is the most important of the
..... Click the link for more information. . The simplest type of transformer consists of two coils of wire, electrically insulated from one another and arranged so that a change in the current in one coil (the primary) will produce a change in voltage in the other (the secondary). In many transformers the coils are wound on a core made of a material with high magnetic permeability; this intensifies the magnetic field induced by the current in the primary, increasing the transformer's efficiency. Neglecting power losses (which are made small by careful design), the ratio of primary voltage to secondary voltage is the same as the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. The primary and secondary currents are in inverse proportion to the number of turns in the coils. The primary and secondary impedancesimpedance,
in electricity, measure in ohms of the degree to which an electric circuit resists the flow of electric current when a voltage is impressed across its terminals.
..... Click the link for more information. are in the same ratio as the squares of the numbers of turns in the primary and secondary coils. For example, if a 10-volt, 2-ampere alternating current were to flow through a 10-turn primary of a transformer, theoretically a 20-turn secondary would exhibit a 20-volt, 1-ampere alternating current, with the output impedance four times as great as the input impedance. Transformers are frequently classified according to their uses; the details of construction depend on the intended application. Power transformers are generally used to transmit power at a constant frequency. Audio transformers are designed to operate over a wide range of frequencies with a nearly flat response, i.e., a nearly constant ratio of input to output voltage. Radio frequency (RF) transformers are designed to operate efficiently within a narrow range of high frequencies.

Transformer

A device that carries electrical current from one source to another, usually with an increase or decrease in voltage.

Transformer

a static device (with no moving parts) for transforming the magnitude of an AC voltage. The operation of a transformer is based on the phenomenon of electromagnetic induction.

A transformer consists of a primary winding, one or more secondary windings, and a ferromagnetic core, or magnetic circuit, which is usually closed (see Figure 1). All the windings are located on the magnetic circuit and are inductively linked (seeMUTUAL INDUCTANCE). Sometimes part of the primary winding serves as the secondary, or vice versa; such transformers are called autotransformers. The terminals of the primary (the transformer input) are connected to a source of AC voltage, and those of the secondary (the output) are connected to the consumers. The alternating current in the primary produces an alternating magnetic flux in the magnetic circuit. In real transformers, part of the magnetic flux is closed outside the magnetic circuit, thereby forming a leakage flux; in high-quality transformers, however, the leakage fluxes are small compared to the mutual flux (the flux in the magnetic circuit).

Figure 1. Simple electrical transformer: (1) and (2) primary and secondary windings, respectively, with w₁ and w₂ turns; (3) core; (Φ₀) mutual flux; (Φ₁) and (Φ₂) leakage fluxes; (l₁) and (l₂) currents in the primary and secondary windings; (U₁) voltage on the primary winding; (R_L) load resistance

The mutual flux Φ₀ produces the electromotive forces (emf’s) e₁ and e₂ in the primary and secondary windings, respectively: e₁ = – w₁dΦ₀/dt, and e₂ = – w₂dΦ₀/dt, where w₁ and w₂ are the number of turns on the corresponding windings. The ratio e₁/e₂ = w₁/w₂ = k is called the turn ratio. The voltages, currents, and emf’s (disregarding the emf’s induced by the leakage fluxes) are associated by the relationships

u₁ + e₁ = i₁r₁

and

u₂ + i₂r₂ = e₂

where r₁ and r₂, u₁ and u₂, i₁ and i₂ are the resistances, voltages, and currents of the windings. If the voltage u₁ applied to the primary is sinusoidal, then the magnetic flux Φ₀ and the emf’s e₁ and e₂ will also be sinusoidal. Therefore, in the analysis of the operation of transformers it is convenient to consider the effective values of the emf’s E₁ and E₂, of the voltages U₁ and U₂, and of the currents I₁ and I₂. For the no-load condition (secondary open), disregarding the resistance of the primary and assuming that I₂ = 0, we will have U₁ + E₁ = 0 and U₂ = E₂, that is (without regard to sign),

The mutual magnetic flux under no-load conditions is produced by the relatively small magnetizing current (the no-load current I₀) in the primary. If the transformer is loaded (the secondary is connected to a load, and current is flowing through it), the magnetomotive force of the secondary (the product I₂w₂) is compensated by a corresponding increase in the magnetomotive force of the primary (I₁w₁ – I₀w₁), and the value of the mutual magnetic flux remains virtually the same as for the no-load condition (that is, the condition U₁ + E₁ = 0 is preserved). Thus, by neglecting the no-load current we obtain I₁w₁ ≈ I₂w₂.

Transformers were first used in 1876 by P. N. lablochkov in electric lighting circuits. In 1890, M. O. Dolivo-Dobrovol’skii developed a three-phase transformer. The subsequent development of transformers produced improvements in design, increases in power and efficiency, and improvement of winding insulation. As of the mid-1970’s, many types of transformers had become commonplace in various fields of technology.

Power transformers are the main type of transformer, and among these the most representative group is the double-wound power transformers, which are used on power lines: Power transformers raise the voltage of the current generated at electric power plants from 10–15 kilovolts (kV) up to 220–750 kV, thus making possible the transmission of electric power over aerial transmission lines for several thousand kilometers. At locations where electric power is consumed, the high voltage is stepped down to low voltages (220 V, 380 V, and so on) by other power transformers. The repeated transformation of the electric power requires a large number of power transformers, and therefore the total power of the transformers in the system is several times that of the sources and power users. High-capacity power transformers have an efficiency of 98–99 percent. Their windings are generally made of copper, and their magnetic circuits of cold-rolled sheets of electrical steel 0.5–0.35 mm thick that have high magnetic permeability and low hysteresis and eddy-current losses. The magnetic circuit and windings of power transformers are usually mounted in a tank filled with mineral oil, which is used to insulate and cool the windings. Such transformers—called oil-filled transformers—are generally located in the open, which requires improved insulation of the leads and hermetic sealing of the tank. Transformers without oil cooling are called dry transformers. For better heat dissipation, power transformers are equipped with a tubular radiator around which the air or, in some cases, water circulates. In lightning-proof transformers the windings are designed so as to avoid the appearance of dangerous voltages across the insulation. Sometimes two or three transformers are connected in series. In many cases transformers with load tap changing are used. Among the dry transformers, low-power transformers with a large number of secondary windings (multiwinding transformers) make up a broad class. They are frequently used in radio engineering apparatus and automatic systems.

In addition to power transformers, there are many types designed to measure high voltages and currents (for example, instrument transformers, voltage transformers, and current transformers), to reduce the level of interference on wire communication lines (negative booster transformers), to convert a sine voltage to a pulse voltage (peaking transformers), to convert current and voltage pulses (peak transformers), to isolate an AC current component, and to decouple and match parts of an electric circuit.

Radio-frequency transformers are used to transform high-frequency voltages; they are made with magnetodielectric magnetic circuits or without a magnetic circuit. In radio transmitters the power of such transformers reaches several hundred kilowatts.

REFERENCES

Petrov, G. N. Elektricheskie mashiny, 3rd ed., part 1. Moscow, 1974.
Vol’dek, A. I. Elektricheskie mashiny. Leningrad, 1974.

V. S. KHVOSTOV

transformer

[tranz′fȯr·mər] (electromagnetism) An electrical component consisting of two or more multiturn coils of wire placed in close proximity to cause the magnetic field of one to link the other; used to transfer electric energy from one or more alternating-current circuits to one or more other circuits by magnetic induction.

transformer

A device with two or more coupled windings, used to convert a supply of electric power at one voltage to another voltage.

transformer

a device that transfers an alternating current from one circuit to one or more other circuits, usually with an increase (step-up transformer) or decrease (step-down transformer) of voltage. The input current is fed to a primary winding, the output being taken from a secondary winding or windings inductively linked to the primary

transformer

A device that is mostly used to change the voltage in an alternating current (AC); however, it can also be used to maintain the same voltage but act as an electrical isolator. The most common type is the laminated core transformer found in power supplies. Made of steel laminations wrapped with two coils of wire, the ratio of windings between the "primary" input coil and the "secondary" output coil determines the voltage change. For example, if the primary has 1,000 windings and the secondary 100, an input of 120 volts is changed to 12v.

Via ElectroMagnetic Induction
There are numerous transformer architectures, and they span the size gamut. Small ones are used in the myriad black boxes that plug into the wall and create low DC voltage for every electronic gadget, while transformers weighing tons are used to transmit 50,000 volts of AC over the nation's power grid. However, they all work via electromagnetic induction. The changing current in the primary coil induces a voltage across the secondary coil.

Switching Power Supplies
The greater the current needed to power the device, the thicker the wire in the coils and the larger the transformer. However, if a high frequency is used, the number of windings can be reduced to make the transformer small. To accomplish this, the incoming voltage is converted to DC (rectified), and a high-frequency oscillator pulses a transistor that passes the rectified voltage as square waves into a "pulse transformer." The on/off DC pulses cause the changing current in the primary coil just the same as AC does. This square wave generation turns a power supply into a "switching power supply." See power adapter, power supply and wall wart.

The Switching Power Supply

In order to reduce the number of windings in transformer coils, a high frequency pulse transformer is used. This is a hypothetical example; voltages and frequencies vary. For example, the oscillator can generate frequencies from 1 kHz to 200 kHz. Following is a simplified circuit diagram of this power supply.

transformer

trans·form·er

transformer

trans•form•er

trans·form·er

transformer

transform

transformer

transformer,

Transformer

Transformer

REFERENCES

transformer

transformer

transformer

transformer

transformer

transformer

transformer

Words related to transformer

noun an electrical device by which alternating current of one voltage is changed to another voltage

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