Thermally responsive metal oxide varistor transient suppression circuit
AssigneeGeneral Electric Company
InventorJohn D. Harnden, Jr.
Life of this patent
Estimating the term…
Abstract
A temperature responsive resistor is thermally connected to a body of metal oxide varistor material in transient suppression and other applications. In the event of excess energy dissipation in the varistor, the temperature of the thermally responsive resistor increases to provide a trigger signal to a triac or other similar electronic switch which may be utilized to provide an alarm, provide increased cooling to the varistor body, to divert, or limit current flow from the varistor. Current flow through the temperature responsive resistor may be provided from a third terminal on the metal oxide varistor in which case the circuit is responsive to both total energy dissipation and peak energy dissipation levels in the varistor.
Claims9
An electrical circuit comprising in combination:
- a body of metal oxide varistor material having at least two electrodes affixed thereto, and
- temperature responsive means thermally connected to said body of varistor material which means function to actuate an electrical switch, connected as a crowbar in shunt with two of said electrodes on said body of varistor material, at such times as the temperature of said body exceeds a predetermined level.
An electrical circuit comprising, in combination:
- a body of metal oxide varistor material;
- temperature responsive means, including a resistor having a negative temperature coefficient, thermally connected to said body of varistor material, which means function to actuate an electrical switch at such times as the temperature of said body exceeds a predetermined level;
- first and second electrodes disposed on the surface of said body of metal oxide varistor material and adapted for connection to a source of electric potential;
- a third electrode disposed on the surface of said body of metal oxide varistor material, intermediate said first and second electrodes, and connected to a first terminal of said resistor;
- and
- a semiconductor switching device having an anode connected to said first electrode, a cathode connected to said second electrode and a gate connected to a second terminal of said resistor.
An electrical circuit element comprising in combination
- a body of varistor material having attached thereto a first terminal, a second terminal, and a third terminal disposed intermediate said first terminal and said second terminal;
- and
- a positive temperature coefficient resistor thermally connected to said body of varistor material and electrically connected between said first terminal and said third terminal.
A varistor circuit element with temperature limiting characteristics comprising:
- a body of metal oxide varistor material;
- at least one body of positive temperature coefficient resistor material bonded to a surface of said body of metal oxide varistor material;
- and
- electrode means disposed on the surfaces of said bodies which function to direct applied electric currents through a series circuit formed by said body of varistor material and at least one of said bodies of resistor material;
- whereby current flow in said body of metal oxide varistor material is limited to prevent excessive temperatures in said material.
Dependencies are inferred from the claim text.