An improved two-stage current transformer

A novel design of magnetic cores and windings of a two-stage current transformer which considerably improves its linearity and accuracy for a given load is discussed. The equations which describe the operation of the transformer are given, and formulas for the calculation of the error are derived. A practical technique for unloading the second core and bringing its magnetic flux near zero is given. Experimental results show that with relatively small cores and a small amount of copper an accuracy better then 20 ppm and 20 mu rd is achieved. The device is passive, with no electronically enhanced technique being implemented. >

[1]  T. Michael Souders,et al.  Wide-Band Two-Stage Current Transformers of High Accuracy , 1972 .

[2]  P. Miljanic,et al.  The development of the current comparator, a high-accuracy A-C ratio measuring device , 1962, Transactions of the American Institute of Electrical Engineers, Part I: Communication and Electronics.

[3]  Eddy So,et al.  An electronically enhanced magnetic core for current transformers , 1990 .

[4]  Warren H. Cook,et al.  - Instrument Transformers , 1970, The Electric Power Engineering Handbook - Five Volume Set.

[6]  H. B. Brooks,et al.  The Two-Stage Current Transformer , 1922, Transactions of the American Institute of Electrical Engineers.