Zero crossing synchronous AC switching circuits employing piezoceramic bender-type switching devices
First Claim
1. A zero crossing synchronous AC switching circuit for alternating current systems employing at least one piezoelectric ceramic bender-type switching device having load current carrying electric switch contacts and at least one prepolarized piezoelectric ceramic bender number for selectively closing or opening the electric switch contacts to control load current flow therethrough, said prepolarized piezoelectric ceramic bender member comprising a pair of planar prepoled piezoelectric ceramic plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of a central conductive surface and having respective outer conductive surfaces that are insulted from each other and the central conductive surface by the respective intervening piezoelectric ceramic plate element thickness, said piezoelectric ceramic bender member further carrying at least one movable contact which coacts with a fixed contact to open and close the electric switch contact means of said switching device, zero crossing sensing circuit means for sensing the passage through zero value of a supply source of alternating current applied across the circuit and for deriving a zero crossing timing signal representative of the occurrence of the zero crossings, bender energization potential control circuit means responsive to the zero crossing timing signals for selectively controlling application and removal of a bender energizing potential across a piezeoelectric ceramic bender member of the bender-type switching device to selectively apply said bender energization potential to each piezoelectric ceramic plate element and having the same polarity as the polarity of the prepole electric field previously permanently induced in said prepoled piezoelectric ceramic plate elements so that no depolarization of said piezeoelectric ceramic plate elements occurs during successive operations of the switching device, and phase shift circuit means effectively responsive to the applied alternating current for shifting the timing of the application and removal of the bender energizing potential to the piezeoelectric ceramic bender member by a preselected phase shift interval relative to the naturally occurring zero crossings of the applied alternating circuit.
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Accused Products
Abstract
Zero crossing synchronous AC switching circuits are provided which employ piezoelectric ceramic bender-type switching devices for use in supplying loads of a resistive, inductive or capacitive nature. The circuits include zero crossing sensing sub-circuits for sensing the passage through zero value of a supply source of alternating current voltage and/or current and for deriving zero crossing timing signals representative of the occurrance of the zero crossings. The zero crossing timing signals are employed to control operation of a bender energizing potential control sub-circuit for selectively controlling application or removal of a bender energizing potential across the piezoelectric bender member of the bender-type switching devices. Phase shift networks are included in the circuit for shifting the phase or time of application of the selectively applied bender energization potential so as to cause it to close or open a set of load current carrying switch contacts substantially at or near the naturally occurring zero crossings of the applied alternating current supplying the load.
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Citations
41 Claims
- 1. A zero crossing synchronous AC switching circuit for alternating current systems employing at least one piezoelectric ceramic bender-type switching device having load current carrying electric switch contacts and at least one prepolarized piezoelectric ceramic bender number for selectively closing or opening the electric switch contacts to control load current flow therethrough, said prepolarized piezoelectric ceramic bender member comprising a pair of planar prepoled piezoelectric ceramic plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of a central conductive surface and having respective outer conductive surfaces that are insulted from each other and the central conductive surface by the respective intervening piezoelectric ceramic plate element thickness, said piezoelectric ceramic bender member further carrying at least one movable contact which coacts with a fixed contact to open and close the electric switch contact means of said switching device, zero crossing sensing circuit means for sensing the passage through zero value of a supply source of alternating current applied across the circuit and for deriving a zero crossing timing signal representative of the occurrence of the zero crossings, bender energization potential control circuit means responsive to the zero crossing timing signals for selectively controlling application and removal of a bender energizing potential across a piezeoelectric ceramic bender member of the bender-type switching device to selectively apply said bender energization potential to each piezoelectric ceramic plate element and having the same polarity as the polarity of the prepole electric field previously permanently induced in said prepoled piezoelectric ceramic plate elements so that no depolarization of said piezeoelectric ceramic plate elements occurs during successive operations of the switching device, and phase shift circuit means effectively responsive to the applied alternating current for shifting the timing of the application and removal of the bender energizing potential to the piezeoelectric ceramic bender member by a preselected phase shift interval relative to the naturally occurring zero crossings of the applied alternating circuit.
- 24. A zero crossing synchronous AC switching circuit for AC systems supplying reactive loads, said zero crossing synchronous AC switching circuit comprising at least one piezoelectric ceramic bender-type switching device having load current carrying switch contacts and at least one prepolarized piezoelectric ceramic bender member for selectively closing or opening the electric switch contacts to control load current flow to a reactive load connected thereto, said prepolarized piezoelectric ceramic bender member comprising a pair of planar prepoled piezoelectric ceramic plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of a central conductive surface and having respective outer conductive surfaces that are insulated from each other and the central conductive surface by the respective intervening piezoelectric ceramic element thickness, said piezoelectric ceramic bender member further carrying at least one movable contact which coacts with a fixed contact to open and close the electric switch contact means of said switching device, voltage zero crossing sensing circuit means for sensing the passage through the zero voltage value of a supply source of alternating current applied across the circuit and for deriving a voltage zero crossing timing signal representative of the occurrence of the voltage zero crossings, current zero crossing sensing circuit means for sensing the passage through zero current value of load current flowing through the load current carrying contacts of the switching device while closed and for deriving a current zero crossing timing signal representative of the occurrence of the current zero crossings, logic circuit means responsive to the voltage and current zero crossing timing signals for use in deriving bender energization control signals representative of the desired time of closure and opening of the load carrying electric switch contacts of the bender-type switching device, phase shift circuit means for shifting the timing of the bender energization control signals by a predetermined phase shift interval relative to the naturally occuring zero crossing of the applied alternating current and voltage, user operated on-off switch means connected to said logic circuit means for selectively enabling and disenabling said logic circuit means and acting in conjunction with said voltage and current zero crossing timing signals to derive the bender energization control signals, output drive amplifier circuit means responsive to the bender energization control signals from said logic circuit means for deriving relatively high voltage electric bender energization potentials to selectively apply said bender energization potentials to each piezoelectric ceramic plate element and having the same polarity as the polarity of the prepoled piezoelectric ceramic plate elements so that no depolarization of said piezoelectric ceramic plate elements occurs during successive operations of the switching device, and means for coupling the piezoelectric ceramic bender member of the bender-type switching device to the output from the output drive amplifier circuit means for selectively energizing or de-energizing the bender member in response to the bender energization control signals from said logic circuit means to cause the load current carrying switch contacts to close or open at or near the zero crossings of the supply alternating current.
- 36. A piezoelectric ceramic bender-type switching device bender member energizing potential control circuit including means for initially including a relatively slow R-C time constant charging resistor in the DC current charging path for applying energizing potential to a bender member plate element of the piezoelectric ceramic switching device and load current controlled bender voltage control means responsive to low initial values of load current flow through the load current carrying contacts of the switching device for almost instantly removing the slow R-C time constant charging resistor from the DC charging current path and increase constant charging resistor from the DC charging current path and increase the voltage value of the energizing potential applied to the bender member to substantially the full voltage value obtainable from the DC energizing potential source to thereby to enhance contact closure and reduce contact bounce and to increase contact compressive force after initial contact closure.
- 40. A bender member potential control system for a switching circuit employing at least one piezoelectric ceramic bender-type switching device having load current carrying electric switch contacts and at least one prepolarized piezoelectric ceramic bender member for selectively closing or opening the electric switch contacts to control load current flow therethrough with the prepolarized piezoelectric ceramic bender member being comprised by two separate pizeoelectric ceramic plate elements sandwiched together into a unitary structure with electric conductive surfaces formed on both the inner and outer facing surfaces of the piezoelectric ceramic plate elements, said piezoelectric ceramic bender member further carrying at least one movable contact which coacts with a fixed contact as the means to close or open the electric switch contacts of said switching device, said bender member potential control system including two separate switching circuits with one of the switching circuits being connected to supply prolonged bender energizing potential of indefinite duration to one of the piezeoelectric ceramic plate elements from a bender energization potential supply source and the remaining circuit being connected to supply pulse-like bender energization potential of short time duration to the remaining piezoelectric plate element of the piezoelectric ceramic bender-type switching device for pull-away assistance during current interruption by the bender-type switching device, both bender energization potential being applied with the same polarity as the polarity of the prepoled piezoelectric ceramic plate elements so that no depolarization of said piezoelectric ceramic plate elements occurs during successive operations of the switching device.
Specification