Dynawave Corporation

Universities Research Association, Inc.

Richard D Hance

Edward J Barsotti

Age T Visser

Alexandr L Kristalinski

Leon H Beverly

An improved apparatus and method reduce the harmonic content of AC line and neutral line currents in polyphase AC source distribution networks. The apparatus and method employ a polyphase Zig-Zag transformer connected between the AC source distribution network and a load. The apparatus and method also employs a mechanism for increasing the source neutral impedance of the AC source distribution network. This mechanism can consist of a choke installed in the neutral line between the AC source and the Zig-Zag transformer.

Method and apparatus for reducing the harmonic currents in

An ultrasound therapy device has a hand-held transducer connected to a base unit having a front display and control panel. A control circuit within the base unit is microprocessor-based and enables an operator to select various output modes, intensities and durations. Transducer current, voltage, and phase angle are monitored for servo control, coupling detection, and fault protection of the output from an efficient power amplifier. Among the front panel displays is a percentage of coupling bar graph.

Ultrasound therapy device

An ultrasound therapy device is provided which maintains a selected constant electrical drive power to a transducer regardless of the load on said transducer by means of an analog servo feedback circuit. The device is operable in either a continuous or pulsed mode and if operated in the pulsed mode, both the pulse period and the pulse duration can be selected by the operator. Circuitry is provided to prevent the operator from selecting a pulse duration greater than the selected pulse period. Touch pad input switches may be used to input values of the operating parameters, and the chosen parameters may be displayed on digital readouts on the front panel of the device.

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Elburn, IL, United States of America

Richard D Hance