INTERNAL RESONANT TRANSFORMER WITH DISTRIBUTED OPEN MAGNETIC CORE

Abstract

The on-site dielectric tests on cables and high power electric machines requires the achievement of some medium voltage testing facilities with reduced dimensions and weights, allowing the compensation of the important reactive energy required by the own capacitance of the device under test (DUT) and which could be supplied from low power and low voltage networks. Until now, by using the classical transformers with closed magnetic core and external resonance, these desiderata could not be accomplished. The solution proposed in the paper, applicable to testing voltages up to 60 - 80 kV, appeals to air core or distributed open magnetic core transformers that operate with internal resonance at variable frequency, within the narrow limits (45-65 Hz) imposed by the standards in force. The possibilities offered by the diagram with parallel resonance and variants of open magnetic cores are analyzed by simulation and experiment, aiming at the maximization of the ratio between the reactive power of the DUT and the apparent power absorbed from the variable frequency source

Keywords: resonant transformercapacitive loadopen core