Plasma switch with hollow, thermionic cathode

A plasma switch comprising:

• an enclosure for containing an ionizable gas;
• hollow cathode means, and anode means, disposed inside the enclosure;
• the hollow cathode means axially discharging therefrom an ionized plasma of the gas;
• the anode means being disposed to radially extract electrons from the plasma discharged from the hollow cathode means;
• keeper electrode means disposed between the hollow cathode means and the anode means for sustaining plasma discharge of the gas between the hollow cathode means and the keeper electrode means in response to a first voltage applied to the keeper electrode means;
• and
• control electrode means disposed between the keeper electrode means and the anode means for causing the plasma to extend from the hollow cathode means to the anode means in response to a second voltage applied to the control electrode means, thereby electrically connecting the hollow cathode means and anode means;
• the hollow cathode means, anode means, keeper electrode means, and control electrode means being configured such that the plasma will extend from the hollow cathode means substantially only to the keeper electrode means when the second voltage on the control electrode is changed to be non-positive relative to the cathode means, thereby interrupting the electrical connection between the anode means and the hollow cathode means.

An inverter/converter, comprising:

• direct current power source means;
• voltage transformer means having primary winding means connected in circuit with the power source means, and secondary winding means;
• rectifier means connected in circuit with the secondary winding means;
• and
• at least one plasma switch connected in circuit to connect the power source means to the primary winding means in response to an applied electrical switching signal, each said plasma switch including:
• an enclosure for containing an ionizable gas;
• thermionic hollow cathode means, and anode means, disposed inside the enclosure;
• the hollow cathode means axially discharging therefrom an ionized plasma of the gas;
• the anode means being disposed to extract electrons from the plasma discharged from the hollow cathode means;
• keeper electrode means disposed between the hollow cathode means and the anode means for sustaining plasma discharge of the gas between the hollow cathode means and the keeper electrode means in response to a first voltage applied to the keeper electrode means;
• and
• control electrode means disposed between the keeper electrode means and the anode means for causing the plasma to extend from the hollow cathode means to the anode means in response to the switching signal, whereby the voltage of the control electrode means is made positive relative to the hollow cathode means thereby electrically connecting the hollow cathode means and the anode means with a low forward voltage drop, the pressure of the ionizable gas being low enough to maintain voltage standoff between the control electrode and the anode means;
• the hollow cathode means, anode means, keeper electrode means, and control electrode means being configured such that the plasma will extend from the hollow cathode means substantially only to the keeper electrode means when the switching signal applied to the control electrode makes the voltage of the control electrode non-positive relative to the cathode means, thereby interrupting the electrical connection between the anode means and the hollow cathode means thereby disconnecting the anode means from the hollow cathode means.

An inverter/converter, comprising:

• direct current power source means;
• voltage transformer means having primary winding means connected in circuit with the power source means, and secondary winding means;
• rectifier means connected in circuit with the secondary winding means;
• and
• at least one plasma switch connected in circuit to connect the power source means to the primary winding means in response to an applied electrical switching signal, each said plasma switch including:
• an enclosure for containing an ionizable gas;
• hollow cathode means, and anode means, disposed inside the enclosure;
• the hollow cathode means axially discharging therefrom an ionized plasma of the gas;
• the anode means being disposed to radially extract electrons from the plasma discharged from the hollow cathode means;
• keeper electrode means disposed between the hollow cathode means and the anode means for sustaining plasma discharge of the gas between the hollow cathode means and the keeper electrode means in response to a first voltage applied to the keeper electrode means;
• and
• control electrode means disposed between the keeper electrode means and the anode means for causing the plasma to extend from the hollow cathode means to the anode means in response to a second voltage applied to the control electrode means which makes the control electrode positive relative to the hollow cathode means, thereby electrically connecting the hollow cathode means and anode means;
• the hollow cathode means, anode means, keeper electrode means, and control electrode means being configured such that the plasma will extend from the hollow cathode means substantially only to the keeper electrode means when the second voltage on the control electrode is changed to make the control electrode non-positive relative to the hollow cathode means. PG,33