Electricity: power supply or regulation systems – Including a transformer or an inductor – With compensation
Patent
1986-03-14
1986-12-16
Wong, Peter S.
Electricity: power supply or regulation systems
Including a transformer or an inductor
With compensation
323347, 324127, H01F 4006
Patent
active
046299742
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an active current transformer of the type having a primary winding conveying current to be measured 1; with W.sub.1 turns and a secondary winding conveying measuring current I.sub.2 with W.sub.2 turns and a detector winding coupled with the secondary winding whereby means of a variable gain amplifier, the induced voltage of the detector winding creates a current in the secondary winding, the magnetic flux of which compensates the magnetic flux permeating the detector winding and produces large current transforming ratio.
DESCRIPTION OF PRIOR DISCLOSURES
Current transformers with electronic error compensation are known for example, from German Pat. No. 23 30 048. In such current transformers the coupling factor K, which is solely determined by means of the magnetic conductance values, is always practically one. This is achieved through the closed magnetic circuit, so that the transforming ratio of the transformer is determined by the ratio of the number of turns of the primary- and of the secondary windings. A remaining slight current error is eliminated through the compensation of the magnetic flux. In the case of high transforming ratios with correspondingly high circulations, this current transformer requires considerable material and space, since the entire primary flux has to be compensated.
In particular during the measuring of the current intensities of high alternating currents, circulations of considerably higher orders of magnitude are produced by the primary winding than transformers, equipped with a ferromagnetic core, require for the faultless functioning of the magnetic core. For the reduction of the expenditure required hereby in magnetic material, as well as reduce space- and cost-requirements, transformers also are known, whose magnetic core surrounds only a portion of the cross-sectional area of the conductor carrying the measuring current. Particular problems arise thereby in regard to the relatively high temperature dependence and the necessity of eliminating principle-conditioned phase errors between the primary- and secondary-current through special measures.
There is known also, an active current transformer where the current to be measured is distributed over two conductors which are separated from one another, which are wound in the opposite sense of direction for the formation of the primary winding and whose resistance values are different from one another German Pat. No. OS 31 40 544).
Moreover, active current transformers are known which completely dispense with the ferromagnetic cores (see German Pat. No. OS 28 12 303), and where the secondary winding is toroidal and, through which the primary conductor carrying the measuring current passes through. Although such transformers operate relatively accurately, their mechanical design is too expensive for mass production.
In the case of the known current transformers, coupling factor K=1 between the primary as well as the secondary winding is always, whereby the transforming ratio is solely determined by the ratio of the number of turns of these windings.
OBJECTS OF THE INVENTION
The invention is to provide a current transformer the main object of which, in comparison to known transformers, can be designed more simply and can be produced more economically while performing at least as well from the viewpoint of measuring technique.
Other objects of the invention will be obvious from the following description of the heat modes of the invention.
SUMMARY OF THE INVENTION
In the current transformer designed according to the invention, the current transforming ratio, in contrast to the known arrangements, is not exclusively determined by the ratio of the number of turns of the primary and secondary winding, but is moreover determined to a considerable measure by the coupling factor, which indicates the ratio of partial flux to total flux. Through the selection of a coupling factor which lies considerably below one, the transforming ratio can be adjusted within wide limits with
REFERENCES:
patent: 3916310 (1975-10-01), Stark et al.
Dr. Richard Feldtkeller, "Spulen und Uebertrager", published by S. Hirzel Verlag, Zurich/1949, pp. 26 & 27.
LGZ Landis & Gyr Zug AG
Wong Peter S.
LandOfFree
Active current transformer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Active current transformer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Active current transformer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-246816