An inverter apparatus includes a liquid path in which cooling water flows, and in which the cooling water performs cooling at a cooling part located directly underneath the power circuit part of the inverter apparatus. The first and second roller pairs have respective first and second drive rollers disposed inwardly of respective curved sections of the curved feed guides and respective first and second driven rollers. Loading conditions for each collartool of the BHA may be determined, such as by use of a beam model, and may be applied to the finite element models for the collartool to determine the fatigue damage of each fatigue susceptible feature of each collartool. A sintered body of the niobium powder.