Abstract: An electric machine system includes a resonant switching system for selecting a resonant frequency of at least a portion of the circuit of the system. The electric machine system includes a first pair of windings for generating force to actuate a moving body and a second pair of windings for exciting the first pair of windings. The resonant switching system includes a resonant inductor and a resonant capacitor. The carrier signal used to excite one of the pairs of windings may have a frequency that is substantially equal to the resonant frequency of the circuit. Preferably, the air gap magnetic flux distribution for the pairs of windings are substantially alike. The electric machine system may employ a rotating body or alternatively may employ a linearly actuating body.

Abstract: In a fluid filled tube, a technique for absorbing or generating converted energy from a traveling sonic wave.The disclosed embodiment employs an acoustic energy converter mechanism and sonic wave channels which are both placed in the walls of the tube. The acoustic energy converter mechanism has faces which are exposed to the sonic wave channels rather than the annulus of the tube. The sonic wave channels allow the mechanical acoustic energy converter mechanism to be reduced in length, yet still expose the faces of the acoustic energy converter mechanism to sonic waves which are 180 degrees out of phase. The acoustic energy mechanism of this invention preferrably uses springs which substitute for the fluid medium of the quarterwave transformer cavity. These springs are designed to simulate a fluid having a sonic impedance and propagation velocity which will make the acoustic energy converter mechanism more compact.

Abstract: The system is described in connection with the control of downhole oil well drilling tools or instruments used in the oil drilling industry. Control wiring extends through the drill pipe employing magnetic coupling between pipe sections. Signal enforcers are provided at predetermined positions along the drill pipe to reinforce all signals communicated via the control wiring. These signal enforcers or repeaters are powered by an acoustic power transmission system which also provides operating power for the tools and instrumentation in the bottom of the well. The power transmission system includes an acoustic power generator or preferably a pair thereof disposed at the top of the drill pipe for establishing a plane acoustic pressure wave that propagates down the drill pipe, and one or more acoustic energy converters including means for converting a portion of the pressure wave to a DC voltage for powering each repeater.