A half phase or full phase arm assembly for a power inverter, comprising: a heat exchanger assembly ; a plurality of electrical components thermally coupled to said heat exchanger assembly ; a number of electrical buses ; wherein each electrical component is coupled to, and in electrical communication with, one said electrical bus ; said plurality of electrical components includes a generally planar semiconductor power switch ; said heat exchanger assembly includes a generally planar heat sink ; said number of electrical buses includes a generally planar bus body ; said semiconductor power switch is directly coupled to said heat sink with the planes of the semiconductor power switch and the heat sink being generally parallel; and said bus body is coupled to said semiconductor power switch with the planes of the bus body and the semiconductor power switch being generally perpendicular, such that the general cross-sectional shape of the assembly of the semiconductor power switch planar body and the generally planar bus body is T-shaped; and a sealing compound applied to each said electrical bus and to a limited number of said electrical components ; wherein the sealing compound is shaped to follow the contour of said electrical bus and the contour of the limited number of enclosed components, such that the sealing compound has a generally T-shaped cross-section; said limited number of said electrical components having a sealing compound applied thereto are enclosed components and any component without sealing compound applied thereto is an exposed component; said enclosed components are substantially sealed from an atmosphere; said enclosed components are coupled to said heat sink by a removable coupling assembly; said sealing compound includes a number of fastener passages; and each said fastener passage is aligned with a heat sink removable coupling assembly . a heat exchanger assembly ; a plurality of electrical components thermally coupled to said heat exchanger assembly ; a number of electrical buses ; wherein each electrical component is coupled to, and in electrical communication with, one said electrical bus ; said plurality of electrical components includes a generally planar semiconductor power switch ; said heat exchanger assembly includes a generally planar heat sink ; said number of electrical buses includes a generally planar bus body ; said semiconductor power switch is directly coupled to said heat sink with the planes of the semiconductor power switch and the heat sink being generally parallel; and said bus body is coupled to said semiconductor power switch with the planes of the bus body and the semiconductor power switch being generally perpendicular, such that the general cross-sectional shape of the assembly of the semiconductor power switch planar body and the generally planar bus body is T-shaped; and a sealing compound applied to each said electrical bus and to a limited number of said electrical components ; wherein the sealing compound is shaped to follow the contour of said electrical bus and the contour of the limited number of enclosed components, such that the sealing compound has a generally T-shaped cross-section; said limited number of said electrical components having a sealing compound applied thereto are enclosed components and any component without sealing compound applied thereto is an exposed component; said enclosed components are substantially sealed from an atmosphere; said enclosed components are coupled to said heat sink by a removable coupling assembly; said sealing compound includes a number of fastener passages; and each said fastener passage is aligned with a heat sink removable coupling assembly . <EOS>