Abstract: An electric machine includes a housing, a rotor rotatably supported by the housing for rotation about a longitudinal axis and a stator assembly fixed secured to the housing spaced apart from a surface of the rotor and concentric with the rotor about the longitudinal axis. The stator assembly includes a stator winding comprising circumferentially spaced apart stator teeth about the longitudinal axis, the stator teeth having remote ends proximate the surface of the rotor. A plurality of sealed cooling channels extend parallel to the longitudinal axis and are disposed between remote ends of successive teeth. The cooling channels are formed in resin of the stator assembly, the cooling channels being fluidly connected to ports in a closed system to circulate cooling fluid to cool the stator assembly and configured to remove heat from the stator assembly proximate the rotor surface. Other aspects include methods of making such machines.

Abstract: A method and apparatus for nondestructive testing of a gas discharge tube (GDT) comprising: electrically connecting a first terminal of the GDT to a first port of a vector network analyzer (VNA); electrically connecting a second terminal of the GDT to a second port of the VNA; measuring S parameters with the VNA; determining GDT capacitance and insertion loss based on the measured S parameters; comparing the determined capacitance and insertion loss of the GDT with a threshold value to determine if the GDT is functional.

Abstract: A method and apparatus for nondestructive testing of a gas discharge tube (GDT) comprising: electrically connecting a first terminal of the GDT to a first port of a vector network analyzer (VNA); electrically connecting a second terminal of the GDT to a second port of the VNA; measuring S parameters with the VNA; determining GDT capacitance and insertion loss based on the measured S parameters; comparing the determined capacitance and insertion loss of the GDT with a threshold value to determine if the GDT is functional.

Abstract: An electric machine includes a housing, a rotor rotatably supported by the housing for rotation about a longitudinal axis and a stator assembly fixed secured to the housing spaced apart from a surface of the rotor and concentric with the rotor about the longitudinal axis. The stator assembly includes a stator winding comprising circumferentially spaced apart stator teeth about the longitudinal axis, the stator teeth having remote ends proximate the surface of the rotor. A plurality of sealed cooling channels extend parallel to the longitudinal axis and are disposed between remote ends of successive teeth. The cooling channels are formed in resin of the stator assembly, the cooling channels being fluidly connected to ports in a closed system to circulate cooling fluid to cool the stator assembly and configured to remove heat from the stator assembly proximate the rotor surface. Other aspects include methods of making such machines.