a line - frequency rotary transformer is provided , including a primary core and a secondary core . the primary core is magnetically couplable to the secondary core . the primary core includes a first plurality of e - core steel laminates arranged in a first ring couplable to a stator . the primary core includes a primary winding disposed within the first ring and configured to transmit line - frequency ac power . the secondary core includes a second plurality of e - core steel laminates arranged in a second ring couplable to a gantry . the gantry is rotatably couplable to the stator . the secondary core includes a secondary winding disposed within the second ring and is configured to receive a line - frequency ac power induced in the secondary winding through the primary core and the secondary core by the primary winding .