Permanent magnets (PMs) have become increasingly popular and are used in many applications including hybrid electric vehicles, motors, generators, and most consumer electronic devices. The design of the magnetic circuit and the actual magnetic properties of the PMs have a significant impact on the performance of the magnetic systems. This is especially true for most rotatory machines including motors and generators. This presentation will introduce a few rotary machine design examples using EEC 18-T550 magnet material, which enables future rotary machines to operate at higher efficiencies, power densities, and reliability: high temperature magnetic bearing for supercritical-carbon dioxide (S-CO2) turbine machinery in a 700°C, 2,000 psi, S-CO2 environment; high temperature magnetic coupler to stir the molten salt and keep the liquid moving inside the vessel of new nuclear reactor at 700~1,000°C; and high temperature brushless DC motor capable of 5kW of power operating at 538°C with maximum speed of 25,000 rpm. Numerical finite element analysis (FEA) is conducted to design the magnetic circuit, which is compared to test data.