New Inductive Current Transformers Provided for to Work at a Frequency of up to 300 kHz

Abstract

Phenomena occurring in electromagnetic current transformers operating in the areas of medium frequencies have been discussed, above all, with respect to the properties of particular constructional solutions. These constructions are characterized by appropriate solutions to windings and special magnetic materials (amorphous and nanocrystalline tapes). The degree of magnetic coupling that occurs between the primary winding and the secondary winding with a definite geometry of the magnetic core was assumed to be the criterion of a solution of the current transformer. Current transformers should be divided into three basic groups: 1) transformers with very small dispersion (i.e. of very good magnetic coupling between the windings); 2) transformers with medium dispersion; 3) transformers with very large dispersion. Current transformers can be assigned specified courses of the magnetic induction Bm as a function of pulsation ω. These courses are closely related to the construction of a given transformer. Thus, it can be stated that the specified variability of the magnetic induction Bm as a pulsation function which affects active losses and passive power has a direct effect on the core temperature and the transformer errors. Hence, the character of changes in Bm=f(ω) is the basic criterion determining the possibility of use of a given solution of the transformer in circuits of a specified elevated frequency. The possibility of application of a conventional current transformer to operate over the range of an elevated frequency is also determined by the value of the rated magnetic induction Bm in the magnetic core. Ill. 2, bibl. 4 (in English; summaries in Lithuanian, English and Russian).