A-c energizing system with static interrupter

Claim 2

An energizing system for passing AC energy from an inverter over a filter which includes a capacitor coupled in series with an inductor, the reactances of the capacitor and inductor being substantially equal at the normal frequency of the inverter AC output voltage, including the improvement which comprises: coupling means, having a first portion coupled in parallel with one of the reactive components of the filter, and having a second portion magnetically coupled to the first portion; a static switch, including a reference impedance of very low value, and at least one semiconductor switch, connected such that conduction of the semiconductor switch effectively couples the reference impedance over the coupling means to substantially short out the filter component coupled in parallel with the first portion of the coupling means; and a firing circuit, connected to provide a control signal for turning on the semiconductor switch upon detection of an overload condition associated with the inverter.

Claim 3

An energizing system having an inverter energized from a DC bus, the inverter passing AC energy over a filter which includes a capacitor series-coupled with an inductor, with the reactances of the capacitor aNd inductor being substantially equal at the normal frequency of the inverter AC output voltage, including the improvement which comprises: a transformer, having a first winding coupled across the capacitor, a second winding magnetically coupled to the first winding, and a center tap connection on the second winding; means including a rectifier for coupling the DC bus to the second winding of the transformer, to clamp the voltage across the capacitor at the DC bus level when the capacitor voltage tends to increase; a static switch, including a diode coupled in series with a semiconductor switch between a pair of reference conductors, a low impedance coupled between the same reference conductors, and means for coupling the center tap connection of the second transformer winding to the common connection between the diode and the semiconductor switch, such that conduction of the semiconductor switch couples the low impedance across the transformer to shunt the capacitor in the filter; and a firing circuit, including a second semiconductor switch connected to be gated on when a signal denoting an overload condition is received by the firing circuit, and means for providing a supply voltage in the firing circuit, such that conduction of the second semiconductor switch passes the supply voltage to gate on the semiconductor switch in the static switch, effectively de-tuning the filter and reducing the AC current flow from the inverter.

Claim 4

An energizing system having an inverter energized from a DC bus, the inverter passing AC energy over a filter which includes a capacitor series-coupled with an inductor, with the reactances of the capacitor aNd inductor being substantially equal at the normal frequency of the inverter AC output voltage, including the improvement which comprises: a transformer, having a first winding coupled across the capacitor, a second winding magnetically coupled to the first winding, and a center tap connection on the second winding; means including a rectifier for coupling the DC bus to the second winding of the transformer, to clamp the voltage across the capacitor at the DC bus level when the capacitor voltage tends to increase; a static switch, including a diode coupled in series with a semiconductor switch between a pair of reference conductors, a low impedance coupled between the same reference conductors, and means for coupling the center tap connection of the second transformer winding to the common connection between the diode and the semiconductor switch, such that conduction of the semiconductor switch couples the low impedance across the transformer to shunt the capacitor in the filter; and a firing circuit, including a second semiconductor switch connected to be gated on when a signal denoting an overload condition is received by the firing circuit, and means for providing a supply voltage in the firing circuit, such that conduction of the second semiconductor switch passes the supply voltage to gate on the semiconductor switch in the static switch, effectively de-tuning the filter and reducing the AC current flow from the inverter.

Claim 5

An energizing system as claimed in claim 2 in which the firing circuit further comprises a relay, connected for actuation upon firing of the second semiconductor switch, to interrupt the energy transfer circuit between the filter and an AC load at a predetermined time after firing of the semiconductor switch in the static switch.