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Quadrature current transformer

Stan Zurek, Quadrature current transformer, Encyclopedia Magnetica,
reviewed by Jeanete Leicht, 2013-01-18

Quadrature current transformer, quadrature transformer1), air-gap transformer2), compensator3), transactor4) or transreactor5) - a type of current transducer with magnetic core which has a significant air gap6) The output signal of such a transformer is voltage (rather than current as it is for an ordinary current transformer).

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Simplified configuration of a quadrature current transformer with a significant air gap in the magnetic core7)

The flux density in the magnetic circuit is almost directly (linearly) proportional to the magnetising primary current. The output voltage across the secondary winding is proportional to the rate of change of the flux density, hence also to the rate of change of primary current.

For sinusoidal signals the secondary voltage lags the primary current by 90° or those signals are in quadrature, hence the name.8)

From theoretical viewpoint the operation of a quadrature current transformer is similar to that of a Rogowski coil. For this reason if countermeasures are not taken and the output voltage is measured directly the accuracy of current measurement is reduced for distorted waveforms due to the influence of higher harmonics. This can be compensated by using for instance passive9) or active integrators.10) Quadrature transformers are used in protection of electric circuits, especially the high-power grid.11)12)

In some applications the air gap can be distributed, for instance by employing magnetodielectric materials.13)

The invention of a “quadrature transformer” is credited to Wiliam Edward Sumpner, who used this device as a part of his wattmeter in 1907.14)

See also

5) Marek Brożyna, Jerzy Witold Nowakowski, Ryszard Nowicz, Application of transreactors for measuring short circuit currents'', 6th International Symposium on Short-Circuit Currents in Power Systems, Beyne-Heusay 1994, p. 3.1.1
9) Jerzy Witold Nowakowski, Transreactor with passive integrator, (in Polish: Transreaktor z integratorem pasywnym), Pr. Nauk. PWarsz., 1991 Konferencje z.1, p. 293, XXIII Międzyuczelniana Konferencja Metrologów MKM'91
10) Jerzy Nowakowski, Measurement current converters with electronic compensation of errors - activated transreactors, (in Polish: Pomiarowe przetworniki prądu na napięcie z elektroniczną kompensacją błędów - transreaktory aktywne), Metrol. Syst. Pomiar. 1993 nr 16 s.223-228, MKM'93. XXV Międzyuczelniana Konferencja Metrologów. Metrologia i Systemy Pomiarowe. Warszawa-Gliwice 1993
11) Jerzy Witold Nowakowski, Marek Brożyna, Transreactor as a current/voltage measuring converter in modern protection systems, (in Polish: Transreaktor jako pomiarowy przetwornik prądu na napięcie w nowoczesnych układach zabezpieczeniowych), Przegląd Elektrotechniczny, 1995 (71/10), p. 260
13) Jerzy Nowakowski, Transreactors with magnetodielectric cores, (in Polish: Transreaktory z rdzeniami z magnetodielektryków), Pomiary Automatyka Kontrola, 1990 (36/1), p.6-9
quadrature_current_transformer.txt · Last modified: 2021/04/15 23:19 by stan_zurek

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