Ratio Transformer and its Calibration
Rae Duk Lee, Han‐Jun Kim, Yu. P. Semënov · 2004
A ratio transformer has been developed with currents from internal loading being compensated by means of auxiliary adjustable current sources connected in accordance with a proposed "parallel" equivalent circuit. The compensating currents are injected to section taps of the coaxial screen of a ratio winding. The application of a splitted magnetic system eliminates necessity of magnetic shielding of the transformer. The additional section with double shielding and adjustable potential provides self-calibration with uncertainty about 10-9. The results of self-calibration have shown that the errors of the decade voltage ratio do not exceed 20 nV/V (in-phase) and 50 nrad (quadrature) at 1 kHz