A cooling system (11) is provided for electrical components (10, 90) in which passageways (21) are inserted in non-magnetic cores of the electrical components, and in which the passageways (21) provide both inflow and outflow of a cooling medium. The passageways (21) can be formed by drilling holes in a core of an electrical component or by mounting closed-end tubes (16 19) on a base plate-cooling manifold (20) or can be part of a conduit assembly (70). The tubes (16 19, 71) are split-flow closed-end tubes inserted from one end of the electrical component (10, 90). The tubes and passageways (16 19, 21, 71) may be partitioned into two halves or into two concentric portions. O-ring seals (28) are provided around the base of the tubes to seal the areas where the passageways communicate with hollow portions of base plates for supplying the cooling medium.