Theory of Current Transformer

Theory of Current Transformer Points : Theory of Current Transformer For satisfactory and accurate performance it is necessary that the ratio of transformer of the instrument transformer should he constant within close limits however, in practice, it is found that neither current transformation ratio I_i/I₂ (in case of current transformers) nor voltage transformation ratio V/V₂ (in case of potential transformers) remains constant. The transformation ratio is found to depend on the exciting current as well as the current an the power factor of the secondary circuit. This fact leads to an error called ratio error of the transformer which depends on the working component of primary.