30 MVA superconducting synchronous condenser has been designed, fabricated, and tested successfully. The test suggested that the new approaches applied to the 30 MVA machine were reasonable. The superconducting field winding composed of six Nb-Ti and two Nb3Sn coils, supported in torque-tube slots by wedges, was excited up to the rated operating current without training. The amplitudes of the rotor vibration were small and special balance at cryogenic temperature was not needed. In this paper, the studies on the key design aspects, namely, superconducting field winding, rotor structural materials, and rotor structures including the connection means between torque-tube(cold) and damper(warm) are described together with the experimental verifications. Moreover, the stator design and the electro-magnetic design including an analysis of the operational performance with regard to double damper system are presented. Machine constants obtained from the theoretical investigations using three-dimensional electro-magnetic field calculations are in good agreement with test results.