Current transformer arrangement for ground fault circuit interrupters

Abstract From the Canadian patent

A sensing current transformer having a single turn primary winding for ground fault circuit interrupters and breakers utilizes a conductive post extending through the transformer metallic enclosure in combination with the conductive path across the metallic closure as the current sensing path. A four turn primary winding is provided by four metallic staples each having, one leg extending through the transformer aperture for, establishing four independent current sensing paths.