The miniature current transformer is a current-type voltage transformer. The primary circuit is connected in series with a resistor and a secondary parallel resistor. The voltage is converted into a current, and after the current is converted by the transformer, the primary output current signal is converted into a required voltage by a sampling resistor. Most of the miniature voltage transformers are plugged into the board for use.
However, the initial permeability is low, and it is not suitable for use in a residual current protection device that requires high initial permeability and sensitivity, for example, an electromagnetic residual current protection device. In addition, amorphous and ultra-fine crystalline materials have defects such as brittle texture and brittle fracture, and appropriate protective measures should be considered in design.