In the case of bushing-type current transformers, the customer’s primary wire is pushed through the current transformer opening in the housing. The push-through opening depends on the size of the primary current.
Wound primary type current transformers have a primary winding and a secondary winding. Both windings are applied on the closed toroidal core and are isolated from each other by insulation. This principle applies mainly where primary currents are small. Low-voltage current transformers for the proportional transformation of large currents to directly measurable smaller current values.