b) Unlike the ideal model, the windings in a real transformer have non-zero resistances and inductances associated with: Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a large transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. Transformers may require protective relays to protect the transformer from overvoltage at higher than rated frequency.

where Z L {\displaystyle Z_{\text{L}}} is the load impedance of the secondary circuit & Z L ′ {\displaystyle Z'_{\text{L}}} is the apparent load or driving point impedance of the primary circuit, the superscript ′ {\displaystyle '} denoting referred to the primary. Winding joule losses and leakage reactance are represented by the following series loop impedances of the model: Natural Language Processing: text classification, named entity recognition, question answering, language modeling, summarization, translation, multiple choice, and text generation.CONCEPTUAL GUIDES offers more discussion and explanation of the underlying concepts and ideas behind models, tasks, and the design philosophy of 🤗 Transformers. Multimodal: table question answering, optical character recognition, information extraction from scanned documents, video classification, and visual question answering. Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage. TUTORIALS are a great place to start if you’re a beginner. This section will help you gain the basic skills you need to start using the library. W h ≈ η β max 1.6 {\displaystyle W_{\text{h}}\approx \eta \beta _{\text{max}}

This article is about the electrical device. For other uses, see Transformer (disambiguation). A basic transformer consisting of two coils of copper wire wrapped around a magnetic core

How to install your Video Doorbell Pro or Pro 2 with a DIN Rail Transformer

Transformer energy losses are dominated by winding and core losses. Transformers' efficiency tends to improve with increasing transformer capacity. [18] The efficiency of typical distribution transformers is between about 98 and 99 percent. [18] [19] One example is in traction transformers used for electric multiple unit and high-speed train service operating across regions with different electrical standards. The converter equipment and traction transformers have to accommodate different input frequencies and voltage (ranging from as high as 50Hz down to 16.7Hz and rated up to 25kV).

Referring to the diagram, a practical transformer's physical behavior may be represented by an equivalent circuit model, which can incorporate an ideal transformer. [16] The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings. [11] Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings. [12] Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load. [11] Transformers are therefore normally designed to have very low leakage inductance. Power transformer overexcitation condition caused by decreased frequency; flux (green), iron core's magnetic characteristics (red) and magnetizing current (blue). c) similar to an inductor, parasitic capacitance and self-resonance phenomenon due to the electric field distribution. Three kinds of parasitic capacitance are usually considered and the closed-loop equations are provided [10] Inclusion of capacitance into the transformer model is complicated, and is rarely attempted; the ‘real’ transformer model's equivalent circuit shown below does not include parasitic capacitance. However, the capacitance effect can be measured by comparing open-circuit inductance, i.e. the inductance of a primary winding when the secondary circuit is open, to a short-circuit inductance when the secondary winding is shorted.In some applications increased leakage is desired, and long magnetic paths, air gaps, or magnetic bypass shunts may deliberately be introduced in a transformer design to limit the short-circuit current it will supply. [12] Leaky transformers may be used to supply loads that exhibit negative resistance, such as electric arcs, mercury- and sodium- vapor lamps and neon signs or for safely handling loads that become periodically short-circuited such as electric arc welders. [9] :485 In normal course of circuit equivalence transformation, R S and X S are in practice usually referred to the primary side by multiplying these impedances by the turns ratio squared, ( N P/ N S) 2=a 2.

Large power transformers are vulnerable to insulation failure due to transient voltages with high-frequency components, such as caused in switching or by lightning. The EMF of a transformer at a given flux increases with frequency. [9] By operating at higher frequencies, transformers can be physically more compact because a given core is able to transfer more power without reaching saturation and fewer turns are needed to achieve the same impedance. However, properties such as core loss and conductor skin effect also increase with frequency. Aircraft and military equipment employ 400Hz power supplies which reduce core and winding weight. [17] Conversely, frequencies used for some railway electrification systems were much lower (e.g. 16.7Hz and 25Hz) than normal utility frequencies (50–60Hz) for historical reasons concerned mainly with the limitations of early electric traction motors. Consequently, the transformers used to step-down the high overhead line voltages were much larger and heavier for the same power rating than those required for the higher frequencies.The resulting model, though sometimes termed 'exact' equivalent circuit based on linearity assumptions, retains a number of approximations. [16] Analysis may be simplified by assuming that magnetizing branch impedance is relatively high and relocating the branch to the left of the primary impedances. This introduces error but allows combination of primary and referred secondary resistances and reactance by simple summation as two series impedances. Air gaps are also used to keep a transformer from saturating, especially audio-frequency transformers in circuits that have a DC component flowing in the windings. [13] A saturable reactor exploits saturation of the core to control alternating current. Core losses are caused mostly by hysteresis and eddy current effects in the core and are proportional to the square of the core flux for operation at a given frequency. [9] :142–143 The finite permeability core requires a magnetizing current I M to maintain mutual flux in the core. Magnetizing current is in phase with the flux, the relationship between the two being non-linear due to saturation effects. However, all impedances of the equivalent circuit shown are by definition linear and such non-linearity effects are not typically reflected in transformer equivalent circuits. [9] :142 With sinusoidal supply, core flux lags the induced EMF by90°. With open-circuited secondary winding, magnetizing branch current I 0 equals transformer no-load current. [16] Instrument transformer, with polarity dot and X1 markings on low-voltage ("LV") side terminal