DC to AC inverter

In a full wave DC to AC inverter having

• a power transformer with primary and secondary windings, the primary winding having a center tap which defines two halves,
• means defining a ground reference potential,
• a battery coupled between the center tap of the primary winding and said ground reference potential,
• first and second SCR inverter switches, one connected between the end terminals of each half of the primary winding and ground, each switch when conductive completing a circuit for current flow from the battery through the associated half of the transformer primary winding,
• a timing signal source connected to the gate elements of each of said SCR inverter switches providing signals which cause said first and second inverter switches to conduct alternately, establishing an alternating current in the secondary winding of said transformer,
• an improved commutating circuit connected to both inverter switches to terminate conduction through the conducting one of the inverter switches prior to initiation of conduction through the other inverter switch, comprising:
• a commutating capacitor;
• a first and second SCR commutation control switch each connected to the commutating capacitor, the first SCR commutation control switch being connected to the terminal of the first SCR inverter switch that is connected to the end terminal of the primary winding, the second SCR commutation control switch being connected to the terminal of the second inverter switch that is connected to the other end of the primary winding;
• means for charging said commutating capacitor coupled with the battery and the center tap of the primary winding;
• and
• means coupled to the gate elements of the first and second SCR commutation control switches for rendering the first SCR commutation control switch conductive before the timing signal causes the first inverter switch to conduct and for rendering the second SCR commutation control switch conductive before the timing signal causes the second inverter switch to conduct, thereby discharging the commutation capacitor alternately across the first and the second inverter switch to terminate conduction therethrough.

In a full wave DC to AC inverter having

• a power transformer with primary and secondary windings, the primary winding having a center tap which defines two halves,
• means defining a ground reference potential,
• a battery coupled between the center tap of the primary winding and said ground reference potential,
• first and second SCR inverter switches, one connected between the end terminals of each half of the primary winding and ground, each switch when conductive completing a circuit for current flow from the battery through the associated half of the transformer primary winding,
• a timing signal source connected to the gate elements of each of said SCR inverter switches providing signals which cause said first and second inverter switches to conduct alternately, establishing an alternating current in the secondary winding of said transformer,
• an improved commutating circuit connected to both inverter switches to terminate conduction through the conducting one of the inverter switches prior to initiation of conduction through the other inverter switch, comprising:
• a commutating capacitor, one end connected to ground;
• a first and a second SCR commutation control switch, each connected to the ungrounded end of the capacitor, the first SCR commutation control switch connected to the terminal of the first SCR inverter switch that is connected to the end terminal of the primary winding, the second SCR commutation control switch connected to the terminal of the second inverter switch that is connected to the other end of the primary winding;
• a commutating capacitor charging transformer having a primary winding connected in series with the battery and the center tap of the primary winding of said power transformer and a secondary winding having one terminal connected to the capacitor and the other terminal controllably couple to ground through an SCR commutating capacitor charging switch, the gate element of the commutating capacitor charging switch being coupled to the timing signal source to conduct when each of said SCR inverter switches conducts;
• and
• means coupled to the gate elements of the first and the second SCR commutation control switches for rendering the first SCR commutation control switch conductive before the timing signal causes the first inverter switch to conduct and for rendering the second SCR commutation control switch conductive before the timing signal causes the second inverter switch to conduct, thereby discharging the commutating capacitor alternately across the first and second inverter switches to terminate conduction therethrough.