Transreactor

Transreactor (abbreviated from the words " transformer " + " reactor " or " transformer reactor ") is a device that is a type of transformer with a non-ferromagnetic gap in the magnetic circuit, while the primary winding of the transreactor is connected in series (like a current transformer ).

Content

1 device
2 Principle of work
3 Application
4 Benefits
5 disadvantages
6 Literature
7 Notes

Device

The transreactor has a primary and one or more secondary windings installed on the magnetic circuit with a gap of non-ferromagnetic material (magnetic circuit with an "air gap"). Thanks to such a device, a transreactor can operate without damage with an open secondary winding (“idle” mode) and a primary winding connected in series, while a similar mode for an electromagnetic current transformer is emergency. The magnitude of the non-ferromagnetic gap δ is selected such that the magnetic core of the transreactor operates in an unsaturated mode.

Principle of Operation

The principle of operation of the transreactor is based on the action of the law of electromagnetic induction , while the secondary current, due to the non-ferromagnetic gap, is so small that it can be assumed that the magnetic flux Φ in the magnetic circuit is generated only by the primary current (primary winding MDS ), in which case:

$\Phi ={\frac {I_{p}\cdot w_{1}}{R_{m}}}$ ${\ displaystyle \ Phi = {\ frac {I_ {p} \ cdot w_ {1}} {R_ {m}}}}$ ,Where

$\Phi$ ${\ displaystyle \ Phi}$ - magnetic flux in the magnetic circuit, $I_{p}$ ${\ displaystyle I_ {p}}$ - primary current, $R_{m}$ ${\ displaystyle R_ {m}}$ - magnetic resistance

Secondary EMF transreactor:

$E_{2}=4,44\cdot w_{1}\cdot \Phi \cdot f=k^{\prime }\cdot \Phi _{1}m=k\cdot I_{1}$ ${\ displaystyle E_ {2} = 4.44 \ cdot w_ {1} \ cdot \ Phi \ cdot f = k ^ {\ prime} \ cdot \ Phi _ {1} m = k \ cdot I_ {1}}$

According to the law of electromagnetic induction, the EMF vector lags behind the flow, and therefore, from the primary current by 90 °:

${\vec {E_{2}}}=-j\cdot k\cdot {\vec {I_{1}}}$ ${\ displaystyle {\ vec {E_ {2}}} = - j \ cdot k \ cdot {\ vec {I_ {1}}}}$

The voltage on the secondary winding is proportional to the current derivative in the primary winding:

$U=E_{2}={\frac {-k\cdot dI}{dt}}$ ${\ displaystyle U = E_ {2} = {\ frac {-k \ cdot dI} {dt}}}$

Parameter $k$ ${\ displaystyle k}$ - has the dimension of resistance (inductive resistance $X_{L}$ ${\ displaystyle X_ {L}}$ ), i.e. transreactor is equivalent to a reactor included in the current circuit $I_{p}$ ${\ displaystyle I_ {p}}$ , which explains the name of this device - a transformer reactor (transformer with output reactor parameters). The presence of a gap creates a proportional relationship between current and voltage in the transreactor, which is impossible in a conventional electromagnetic current transformer due to saturation.

Application

Transreactors are widely used in relay protection circuitry, as devices designed to convert current (derivative of current) to voltage and to perform galvanic isolation.

Benefits

Convert current and derivative current to proportional voltage
The presence of galvanic isolation
Reducing the aperiodic component (which can be used in the differential protection of transformers to reduce the surges of unbalance currents when turned on ^[1] )
Ability to work in idle mode and at high resistance load without damage.

Weaknesses

Relatively small value of the output voltage (due to the presence of a gap in the magnetic circuit, the magnitude of the induced EMF in the secondary winding is small)
Increasing the content of higher harmonics in the secondary voltage (the transreactor is a differentiating element through which high frequencies pass)

Literature

N. V Chernobrovov “Relay protection”, M., “Energy”, 1975

Notes

↑ http://spbet.narod.ru/studies/rz2

https://studopedia.su/9_85111_transreaktor---transformator-toka-s-magnitoprovodom-imeyushchim-vozdushniy-zazor.html

[1] ttp://spbet.narod.ru/studies/rz2