Polyphase control device

Claim 2

In a phase-responsive device, three terminals adapted to be connected to a three-phase electrical source to produce a threephase source of electrical power for the device, a first unidirectional electrical valve having a main current path and a control electrode for controlling the conductivity of the main current path, a current responsive translating device connected in series with said main current path of said first unidirectional electrical valve between first and second ones of said terminals, means connecting the control electrode to the third terminal to render said main current path of the first unidirectional electrical valve means conductive as long as the voltage across the main current path maintains a first polarity once the voltage at the third terminal simultaneously has a first polarity, and the improvement comprising second and third unidirectional electrical valve means connected back to back between said second and third terminals with said series connected main current path of the first unidirectional electrical valve and said translating device being connected to the second and third terminals through the common point between the second and third unidirectional electrical valves, whereby for a given phase rotation of the three phase electrical source the main current path of the first unidirectional electrical valve will be rendered conductive to pass current through the translating device from a point in time when both the first and third phase voltages of the electrical source have said first polarity through the interval that said first terminal maintains said first polarity with respect to either the second or third terminals.

Claim 3

In a phase-responsive device, three terminals adapted to be connected to a three-phase electrical source to produce a three-phase source of electrical power for the device, a first unidirectional electrical valve having a main current path and a control electrode for controlling the conductivity of the main current path, a current responsive translating device connected in series with said main current path of said first unidirectional electrical valve between first and second ones of said terminals, means connecting a control electrode to the third terminal to render said main current path of the first unidirectional electrical valve conductive as long as the voltage across the main current path maintains a first polarity once the voltage at the third terminal simultaneously has a first polarity, and the improvement, comprising a second unidirectional electrical valve having a main current path and a control electrode for controlling the conductivity of the main current path said second unidirectional electrical valve being connected with its main current path in series with the main current path of said first unidirectional electrical valve, an energy storage device connected in parallel with the main current path of the first unidirectional electrical valve, means for charging said energy sTorage device by periodically applying reverse bias to the first unidirectional electrical valve and means for applying the voltage across the energy storage device to the control electrode of the second unidirectional electrical valve, whereby under normal conditions both unidirectional electrical valves will be rendered conductive to supply current to the translating device for a predetermined phase rotation, while no current will be delivered to the translating device should the first unidirectional electrical valve fail as a short circuit.

Claim 4

In a phase-responsive device, three terminals adapted to be connected to a three-phase electrical source to produce a three-phase source of electrical power for the device, a first unidirectional electrical valve having a main current path and a control electrode for controlling the conductivity of the main current path, a current responsive translating device connected in series with said main current path of said first unidirectional electrical valve between first and second ones of said terminals, means connecting a control electrode to the third terminal to render said main current path of the first unidirectional electrical valve conductive as long as the voltage across the main current path maintains a first polarity once the voltage at the third terminal simultaneously has a first polarity, and the improvement, comprising a second unidirectional electrical valve having a main current path and a control electrode for controlling the conductivity of the main current path said second unidirectional electrical valve being connected with its main current path in series with the main current path of said first unidirectional electrical valve, an energy storage device connected in parallel with the main current path of the first unidirectional electrical valve, means for charging said energy sTorage device by periodically applying reverse bias to the first unidirectional electrical valve and means for applying the voltage across the energy storage device to the control electrode of the second unidirectional electrical valve, whereby under normal conditions both unidirectional electrical valves will be rendered conductive to supply current to the translating device for a predetermined phase rotation, while no current will be delivered to the translating device should the first unidirectional electrical valve fail as a short circuit.

Claim 5

The device of claim 2 wherein the main current path of the second unidirectional electrical valve is connected between said first terminal and the main current path of the first unidirectional electrical valve, wherein the energy storage device connected across the main current path of the first unidirectional electrical valve is a capacitor and wherein the means for reverse-biasing the first unidirectional electrical valve comprises means connecting the voltage between the third and first terminals across the main current path of the first unidirectional electrical valve and includes a capacitor shunting the main current path of the second unidirectional electrical valve.

Claim 6

In a phase-responsive device including 3 terminals to be connected to a 3 phrase electrical source, a controlled rectifier having a main current path between an anode and a cathode and a control electrode, a current responsive translating device connected in series with said main current path of said controlled rectifier between first and second ones of said terminals, a pulse generator comprising two junctions, a source of half-wave rectified alternating current connected across said junctions, a unijunction transistor, a resistor, the base b2 of said unijunction transistor being connected to a first one of said junctions and the base b1 being connected to the second junction through the resistor, and a triggering circuit comprising a capacitor connected between the emitter of said unijunction transistor and said second junction, a voltage divider connected across said first and second junctions, a tap on said voltage divider being connected to the emitter of said unijunction transistor for charging said capacitor, the relative values of said voltage divider and capacitor being such that the charge on said capacitor will reach a predetermined voltage in less than 120* of phase rotation after the supply voltage goes positive but at a rate such that the instantaneous voltage on the capacitor during charging maintains the emitter to base b2 voltage ratio below the intrinsic stand off ratio of the unijunction transistor, and a diode connected between the tap on the voltage divider and the emitter of the unijunction transistor for maintaining the charge on the capacitor until it is discharged through the resister when the magnitude of the alternating current voltage drops to a value where the ratio of the predetermined voltage maintained on the capacitor to the instantaneous magnitude of the alternating current supply voltage equals the intrinsic stand off ratio of the unijunction transistor, means connecting said first junction of the pulse generator to said third terminal through a diode to supply positive half cycles of alternating current to the pulse generator, means connecting said second junction of the pulse generator to the cathode of the controlled rectifier and means connecting said control electrode of the controlled rectifier to the base b1 of the unijunction transistor whereby the pulse generator will supply firing pulses to the controlled rectifier while the controlled rectifier is forward biased for a given phase rotation of the three phase electrical source.

Claim 7

In a phase-responsive device including 3 terminals to be connected to a 3 phrase electrical source, a controlled rectifier having a main current path between an anode and a cathode and a control electrode, a current responsive translating device connected in series with said main current path of said controlled rectifier between first and second ones of said terminals, a pulse generator comprising two junctions, a source of half-wave rectified alternating current connected across said junctions, a unijunction transistor, a resistor, the base b2 of said unijunction transistor being connected to a first one of said junctions and the base b1 being connected to the second junction through the resistor, and a triggering circuit comprising a capacitor connected between the emitter of said unijunction transistor and said second junction, a voltage divider connected across said first and second junctions, a tap on said voltage divider being connected to the emitter of said unijunction transistor for charging said capacitor, the relative values of said voltage divider and capacitor being such that the charge on said capacitor will reach a predetermined voltage in less than 120* of phase rotation after the supply voltage goes positive but at a rate such that the instantaneous voltage on the capacitor during charging maintains the emitter to base b2 voltage ratio below the intrinsic stand off ratio of the unijunction transistor, and a diode connected between the tap on the voltage divider and the emitter of the unijunction transistor for maintaining the charge on the capacitor until it is discharged through the resister when the magnitude of the alternating current voltage drops to a value where the ratio of the predetermined voltage maintained on the capacitor to the instantaneous magnitude of the alternating current supply voltage equals the intrinsic stand off ratio of the unijunction transistor, means connecting said first junction of the pulse generator to said third terminal through a diode to supply positive half cycles of alternating current to the pulse generator, means connecting said second junction of the pulse generator to the cathode of the controlled rectifier and means connecting said control electrode of the controlled rectifier to the base b1 of the unijunction transistor whereby the pulse generator will supply firing pulses to the controlled rectifier while the controlled rectifier is forward biased for a given phase rotation of the three phase electrical source.