Inverter for supplying a regulated voltage

Claim 2

An inverter circuit for supplying a regulated DC voltage and characterized by its reliable operation for all load conditions including a short circuit load condition, comprising: a controlled rectifier bridge inverter having a pair of input terminals and a pair of output terminals; a DC voltage source coupled across the input terminals of the inverter; a commutating circuit, the commutating circuit including a commutating capacitor and a commutating inductor series coupled across the output terminals of the inverter, the maximum operating frequency of the controlled rectifier bridge inverter at which required controlled rectifier commutation time is provided being limited by the resonant frequency of the commutating circuit; an output circuit, the output circuit including a full wave bridge rectifier having a pair of input terminals and a pair of output terminals, a second inductor, means series coupling the commutating inductor and the second inductor across the input terminals of the bridge rectifier, and a filter capacitor coupled across the output terminal pair of the bridge rectifier, the filter capacitor being charged through a circuit including the commutating capacitor, the second inductor and the bridge rectifier, the voltage across the filter capacitor comprising the output regulated voltage; load means coupled across the filter capacitor; and means responsive to the voltage across the filter capacitor effective to vary the frequency of operation of the controlled rectifier bridge inverter in a sense to maintain a constant voltage value across the filter capacitor, the last-mentioned means having a predetermined maximum frequency of operation occurring when the load means is short circuited and the filter capacitor is discharged, the commutating capacitor and the commutating inductor defining a commutating circuit resonant frequency that is less than the predetermined maximum frequency when the voltage across the filter capacitor is at the constant voltage value and the commutating capacitor and the parallel combination of the commutating inductor and the second inductor defining a commutating circuit resonant frequency that is greater than the predetermined maximum frequency when the load means is short circuited and the filter capacitor is discharged, the resonant frequency of the commutating circuit being increased to above the predetermined maximum frequency during the period that the load means is short circuited to thereby provide reliable operation of the controlled rectifier bridge inverter for all load conditions including a short circuited load condition.

Claim 3

An inverter circuit for supplying a regulated DC voltage and characterized by its reliable operation for all load conditions including a short circuit load condition, comprising: a bridge inverter, the bridge inverter including first, second, third and fourth controlled rectifiers coupled in a bridge configuration, a pair of input terminals, a pair of output terminals and first, second, third and fourth diodes, each diode being coupled in parallel with a respective one of the controlled rectifiers and poled to conduct current in a direction opposite the direction of current through the controlled rectifier parallel coupled therewith; a DC voltage source coupled across the input terminals of the inverter; a commutating circuit, the commutating circuit including a commutating capacitor and a commutating inductor series coupled across the output terminals of the inverter, the commutating capacitor being charged by the DC voltage source when the controlled rectifiers in opposed sides of the bridge inverter are gated conductive to a value greater than the DC voltage source and thereafter discharging through the diodes parallel coupled with the conductive controlled rectifiers to provide for controlled rectifier commutation, the maximum operating frequency of the controlled rectifier bridge inverter at which required controlled rectifier commutation time is provided being limited by the resonant frequency of the commutating circuit; an output circuit, the output circuit including a full wave bridge rectifier having a pair of input terminals and a pair of output terminals, a second inductor, means series coupling the commutating inductor and the second inductor across the input terminals of the bridge rectifier, and a filter capacitor coupled across the output terminal pair of the bridge rectifier, the filter capacitor being charged through a circuit including the commutating capacitor, the second inductor and the bridge rectifier, the voltage across the filter capacitor comprising the output regulated voltage; load means coupled across the filter capacitor; and means responsive to the voltage across the filter capacitor effective to alternately gate conductive the controlled rectifiers in one pair of opposed sides of the bridge inverter and the controlled rectifiers in the other pair of opposed sides of the bridge inverter at a frequency tending to maintain a constant voltage value across the filter capacitor, the last-mentioned means having a predetermined maximum frequency of operation occurring when the load means is short circuited and the filter capacitor is discharged, the commutating capacitor and the commutating inductor defining a commutating circuit resonant frequency that is less than the predetermined maximum frequency when the voltage across the filter capacitor is at the constant voltage value and the commutating capacitor and the parallel combination of the commutating inductor and the second inductor defining a commutating circuit resonant frequency that is greater than the predetermined maximum frequency when the load means is short circuited and the filter capacitor is discharged, the resonant frequency of the commutating circuit being increased to above the predetermined maximum frequency during the period that the load means is short circuited to thereby provide reliable operation of the controlled rectifier bridge inverter for all load conditions including a short circuited load condition.

Claim 4

An inverter circuit for supplying a regulated DC voltage and characterized by its reliable operation for all load conditions including a short circuit load condition, comprising: a bridge inverter, the bridge inverter including first, second, third and fourth controlled rectifiers coupled in a bridge configuration, a pair of input terminals, a pair of output terminals and first, second, third and fourth diodes, each diode being coupled in parallel with a respective one of the controlled rectifiers and poled to conduct current in a direction opposite the direction of current through the controlled rectifier parallel coupled therewith; a DC voltage source coupled across the input terminals of the inverter; a commutating circuit, the commutating circuit including a commutating capacitor and a commutating inductor series coupled across the output terminals of the inverter, the commutating capacitor being charged by the DC voltage source when the controlled rectifiers in opposed sides of the bridge inverter are gated conductive to a value greater than the DC voltage source and thereafter discharging through the diodes parallel coupled with the conductive controlled rectifiers to provide for controlled rectifier commutation, the maximum operating frequency of the controlled rectifier bridge inverter at which required controlled rectifier commutation time is provided being limited by the resonant frequency of the commutating circuit; an output circuit, the output circuit including a full wave bridge rectifier having a pair of input terminals and a pair of output terminals, a second inductor, means series coupling the commutating inductor and the second inductor across the input terminals of the bridge rectifier, and a filter capacitor coupled across the output terminal pair of the bridge rectifier, the filter capacitor being charged through a circuit including the commutating capacitor, the second inductor and the bridge rectifier, the voltage across the filter capacitor comprising the output regulated voltage; load means coupled across the filter capacitor; and means responsive to the voltage across the filter capacitor effective to alternately gate conductive the controlled rectifiers in one pair of opposed sides of the bridge inverter and the controlled rectifiers in the other pair of opposed sides of the bridge inverter at a frequency tending to maintain a constant voltage value across the filter capacitor, the last-mentioned means having a predetermined maximum frequency of operation occurring when the load means is short circuited and the filter capacitor is discharged, the commutating capacitor and the commutating inductor defining a commutating circuit resonant frequency that is less than the predetermined maximum frequency when the voltage across the filter capacitor is at the constant voltage value and the commutating capacitor and the parallel combination of the commutating inductor and the second inductor defining a commutating circuit resonant frequency that is greater than the predetermined maximum frequency when the load means is short circuited and the filter capacitor is discharged, the resonant frequency of the commutating circuit being increased to above the predetermined maximum frequency during the period that the load means is short circuited to thereby provide reliable operation of the controlled rectifier bridge inverter for all load conditions including a short circuited load condition.