초록 ▼

Method and apparatus for providing alternate current paths to a junction through different sets of gate controlled SCRs coupled to the junction. The method starts with the step of initiating a switch from an active set of SCRs to an inactive set by removing a gate signal from two parallel connected,

Method and apparatus for providing alternate current paths to a junction through different sets of gate controlled SCRs coupled to the junction. The method starts with the step of initiating a switch from an active set of SCRs to an inactive set by removing a gate signal from two parallel connected, opposite sense current carrying SCRs which in combination carry AC current in either direction. Removal of the gating signal is often initiated, for example, in response to an indication that one alternating current source is faulty so that a switch to a second source is initiated. Current is then sensed through the two SCRs of the active set to determine a current carrying state for each of those two SCRs. After the state of the current carrying SCRs is determined the current carrying state of the SCRs is confirmed during a delay time period. If the current carrying state of either of said two SCRs is the same during the delay time period, a gating signal is applied to a corresponding SCR in an inactive set to enable current flow through that corresponding SCR. Once both SCRs in the inactive set have been activated the switch is complete. By waiting until the current has been confirmed during the delay period inappropriate activation of the gate signals of an inactive switch is prevented.

대표청구항 ▼

1. A method for providing alternate current paths to a junction through gate controlled current carrying devices wherein each of said current carrying devices within a set of such devices blocks current flow in one direction and selectively allows current flow in an opposite direction when a gate to

1. A method for providing alternate current paths to a junction through gate controlled current carrying devices wherein each of said current carrying devices within a set of such devices blocks current flow in one direction and selectively allows current flow in an opposite direction when a gate to said devices is activated, said method comprising the steps of:a) initiating a switch away from a first current path through a first, active device set of two or more current carrying devices to a second current path through a second, inactive device set of two or more current carrying devices by removing a current sustaining gate signal from the current carrying devices of the first device set;b) sensing a current status of the devices of the first, active device set to determine a , current carrying status of said devices by monitoring a voltage across the first device set;c) if the voltage falls within a specified range designating at least one of the devices that make up the first active device set as being current carrying and otherwise designating the first active device set as being blocking current in both directions;d) again sensing a voltage across the devices of the first, active device set to confirm the current carrying status of said devices; ande) if the current carrying state of said devices in the first, active device set is confirmed in step d to be in the same state sensed in step c b , and the first active device set is not blocking current in both directions, gating one gate controlled device in a the second, inactive set of said gate controlled devices to enable current flow in one direction through said one gate controlled device of the second, inactive device set. 2. The method of claim 1 wherein the sensing step of step b causes the devices of the first set to be designated as blocking if the voltage across said first set has an absolute value of less than a first voltage or greater than a second voltage. 3. The method of claim 2 wherein the current carrying devices are silicon controlled rectifiers and the first voltage is 0.3 volts and the second voltage is 3 volts. 4. The method of claim 2 wherein if the voltage is less than the first voltage or greater than the second voltage all of the current carrying devices of the inactive device set are gated into conduction in step e. 5. The method of claim 1 wherein if in step b a voltage of greater than a specified value is sensed for longer than a specified duration an error condition is designated. 6. Apparatus for coupling a source to a load through a junction comprising:a) a first set of gate controlled switches coupled to a junction wherein one switch of the first set conducts current in one sense and another switch of the first set conducts current in an opposite sense;b) a second set of gate controlled switches coupled to said junction wherein one switch of the second set conducts current in one sense and another switch of the second set conducts current in an opposite sense;c) a monitoring circuit for monitoring a current status of the switches of the first and second sets of gate controlled switches; said monitoring circuit comprising threshold determining circuits coupled to the switches of a respective device set the first and second sets of gate controlled switches for categorizing a current status of the devices that make up a device set switches as having either i) a positive current carrying state; ii) a negative current carrying state; or iii) a blocking state;d) a first gate control circuit coupled to the switches of the first set of gate, controlled switches and a second gate control circuit coupled to the switches of the second set of gate controlled switches for gating the switches of a selected one of the first and second sets of gate controlled switches into conduction, the selected one of the first and second sets of gate controlled switches comprising an active switch set ; an de) a controller coupled to the first and second gate control circuits for activating switches in the first and second sets of gate controlled switches by actuating the first and second gate control circuits as said controller determines which set of said first and second set sets of gate controlled switches to render select as the active; switch set; said controller also coupled to said monitoring circuits circuit to monitor the current carrying state of the switches of the first and seconds second sets of gate controlled switches; said controller comprising a stored program for changing which of the first and second sets of gate controlled switches is selected as the active switch set by instructing the first and second gate control circuits to remove a gating signal from the gate electrode of a first the switches of the active switch set and subsequent to the removal of the gating signal for repeatedly monitoring an output from the monitoring circuits circuit to confirm a status of the current in the switches of a first the active switch set and subsequent to such confirmation for then applying a gate signal to the gate electrodes of switches in a second of an inactive switch set and thereby allow current to flow through the second switches of the inactive switch set. 7. The apparatus of claim 6 wherein the threshold determining circuit indicates circuits indicate a positive current carrying state if a voltage across a gate controlled switch set falls in one range, the circuit indicates circuits indicate a negative current carrying state if the a voltage across a gate controlled switch set falls in a second range and otherwise indicates a blocking condition. 8. The apparatus of claim 7 wherein the first and second ranges are plus and minus voltages of approximately the same size. 9. The apparatus of claim 6 where the switches are silicon controlled rectifiers and the first and second ranges are from approximately 13 volts to 3 volts. 10. The apparatus of claim 7 where the controller includes timing means for sensing voltages above the first and range or below the second ranges for an extended period and designating such condition as an error condition independent of switch the state of the switch sets. 11. A method for providing alternate current paths to a junction through gate controlled current carrying devices wherein each of said current carrying devices within a set of such devices blocks current flow in one direction and selectively allows current flow in an opposite direction when a gate to a said selected device is activated, and method comprising the steps of: a ) sensing a current status of current carrying devices of a first, active device set to determine a current carrying status of said devices by monitoring a voltage across the first, active device set; b ) in the event the voltage across the first, active device set exceeds an error threshold voltage, initiating a switch away from a first current path through the first, active device set of two or more current carrying devices to a second current path through a second, inactive device set of two or more current carrying devices by removing a current sustaining gate signal from the current carrying devices of the first, active device set; c ) sensing a current status of the devices of the first, active device set to determine a current carrying status of said devices by monitoring a voltage across the first, active device set; d ) if the voltage falls within a specified range designating at least one of the devices that make up the first, active device set as being current carrying and otherwise designating the first, active device set as blocking current in both directions; and e ) if the first, active device set is not blocking current in both directions gating at least one gate controlled device in a second, inactive set of sai d gate controlled devices to enable current flow through said at least one gate controlled device of the second, inactive device set. 12. The method of claim 11, wherein the sensing step of step c causes the devices of the first, active device set to be designated as blocking current if the voltage across said first set has an absolute value of less than a first voltage or greater than a second voltage. 13. The method of claim 12 wherein the current carrying devices are silicon controlled rectifiers and the first voltage is 0 . 3 volts and the second voltage is 3 volts. 14. The method of claim 12 wherein if the voltage is less than the first voltage or greater than the second voltage all of the current carrying devices of the second, inactive device set are gated into conduction in step e. 15. The method of claim 11 wherein if a voltage of greater than the error threshold voltage for the active device set is sensed for longer than a specified duration an error condition is noted. 16. The method of claim 11 wherein the step of initiating a switch away from the first, active device set is performed when the error threshold voltage is sensed for a specified time period. 17. The method of claim 16 wherein the specified time period is on the order of a few milliseconds.