Apparatus and a method for testing winding resistances of transformers

Abstract

The present invention relates to an apparatus for measuring winding resistances of windings in a delta-connected transformer, comprising at least a first and a second DC current source (S1, S2) connected each between the phase ends of a first (A) and a second leg (C; B) respectively of the primary side (P) of the transformer and at least a third DC current source (S3) connected between two nodes (a, b) of the secondary side (S) of the transformer. Furthermore the invention relates to a method for measuring a winding resistance of windings in delta-connected transformers, comprising the steps of applying a first and a second measuring current to each one of two corresponding legs (C, B), applying a third measuring current (I2) between two nodes (b, a) of a pair of windings on the secondary side (S) and measuring at least a winding resistance of the winding between said nodes (b, a) on the secondary side (S) of the transformer and/or the winding resistance of a leg (A) of the primary side (P) as soon as an inductive voltage drop in the windings substantially equals zero.

Dependencies are inferred from the claim text.