A medical system comprising: an internal unit for implantation into a body of a patient; a transformer core to be arranged under the skin of the patient; internal cabling connecting the internal unit and the transformer core, the internal cabling comprising an internal winding around the transformer core; and an external unit to be outside the body of the patient, the external unit comprising power supply circuitry and external cabling coupled to the power supply circuitry for enabling supply of power from the power supply circuitry to the internal unit via the transformer core, characterized in that the external cabling comprises: a connector including a first connector part and a second connector part; a first conductive current path between the power supply circuitry and the first connector part, conductively connecting the first connector part and the power supply circuitry; a second conductive current path between the power supply circuitry and the second connector part, conductively connecting the second connector part and the power supply circuitry; and a third conductive current path between the first connector part and the second connector part, conductively connecting the first connector part and the second connector part, wherein the first connector part and the second connector part are configured to be joined to conductively connect the first conductive current path to the second conductive current path via the third conductive current path so that a second winding can be formed around the transformer core by joining the first connector part and the second connector part. an internal unit for implantation into a body of a patient; a transformer core to be arranged under the skin of the patient; internal cabling connecting the internal unit and the transformer core, the internal cabling comprising an internal winding around the transformer core; and an external unit to be outside the body of the patient, the external unit comprising power supply circuitry and external cabling coupled to the power supply circuitry for enabling supply of power from the power supply circuitry to the internal unit via the transformer core, characterized in that the external cabling comprises: a connector including a first connector part and a second connector part; a first conductive current path between the power supply circuitry and the first connector part, conductively connecting the first connector part and the power supply circuitry; a second conductive current path between the power supply circuitry and the second connector part, conductively connecting the second connector part and the power supply circuitry; and a third conductive current path between the first connector part and the second connector part, conductively connecting the first connector part and the second connector part, a connector including a first connector part and a second connector part; a first conductive current path between the power supply circuitry and the first connector part, conductively connecting the first connector part and the power supply circuitry; a second conductive current path between the power supply circuitry and the second connector part, conductively connecting the second connector part and the power supply circuitry; and a third conductive current path between the first connector part and the second connector part, conductively connecting the first connector part and the second connector part, wherein the first connector part and the second connector part are configured to be joined to conductively connect the first conductive current path to the second conductive current path via the third conductive current path so that a second winding can be formed around the transformer core by joining the first connector part and the second connector part.