Abstract: Over-voltage protection circuits are provided for power supplies that may limit input voltage spikes to a power converter and amplifiers including a damping loop that may damp filter resonance. Active damping systems incorporating the over-voltage protection circuits and/or damping loops of the present invention are also provided which may be particularly advantageous in applications such as aircraft or other vehicle applications where size and power consumption are important design considerations. The over-voltage protection circuit in various embodiments senses AC and/or DC voltage levels above a detection threshold level and momentarily disconnects the voltage input to thereby reduce the maximum voltage level input transients seen by the power converter. A capacitor may be provided to maintain the input voltage to the power converter while the input is switched out.

Abstract: A method, apparatus and controller for machining non-circular work pieces. The apparatus, method and controller are preferably used in combination with rotating, equipment, such as a turning center having an x-y table capable of gross movements. The apparatus includes at least one position sensor for deriving an angular position signal of the work piece, a preferably longitudinally-disposed, flexible tool holder attached to a rigid tool block which holds the machine tool, a preferably solid state vibration actuator imparting active vibrational forces to the end of the tool holder, thus vibrating the machine tool at high frequency to impart the desired ovality to the work piece, and a control system for generating the output signal to the vibration actuator. Preferably, the control system includes manually adjusted magnitude and phase thereby providing a non-circular work piece profile with the desired ovality and positioning thereof.