Grounding system and apparatus

1. A grounding system for a semiconductor module comprising:

a first conductive layer connected to the semiconductor module;

a second conductive layer;

a substrate having a first surface and a second surface opposite the first surface, the substrate disposed between the first conductive layer and the second conductive layer, the substrate being electrically connected on the first surface to the first conductive layer and on the second surface to the second conductive laver, and a base connected to the second conductive layer, the base being electrically connectable to earth ground;

the first conductive layer being separated from the second conductive layer by the substrate; and

wherein the first conductive layer, the substrate and the second conductive layer form a capacitance path between the semiconductor module and the base to reduce parasitic currents generated in the semiconductor module.

2. The system of claim 1 , wherein the semiconductor module is selected from the group consisting of n insulated gate bipolar transistor, (IGBT), bipolar junction transistors (BJT), metal-oxide semiconductor field-effect transistors (MOSFET), semiconductor controlled rectifier (SCR), and other three terminal semiconductor devices.

3. The system of claim 1 , wherein the first conductive layer and the second layer are comprised of an electrically conductive metal selected from the group consisting of copper, aluminum, gold, silver, platinum and alloys thereof.

4. The system of claim 1 , wherein the second conductive layer is affixed to the base by a solder connection about a portion of an interface edge.

5. The system of claim 1 , wherein the substrate layer comprises a ceramic material.

6. The system of claim 1 , wherein the substrate layer comprises a nonconductive material.

7. The system of claim 1 , wherein the base is connected to earth ground by a conductor bonded at one end to the base and at an opposite end to the earth ground or other suitable voltage reference point.

8. A power semiconductor apparatus comprising:

a semiconductor module and associated control circuitry mounted on a base;

a nonconductive heat sink in thermal communication with the base and in fluid communication with a source of liquid; and

a grounding assembly comprising;

a first conductive layer, a second conductive layer; a substrate disposed between the first conductive layer and the second conductive layer; and a base attached to the second conductive layer, the base being connected to earth ground;

the first conductive layer in electrical contact with the semiconductor module and the substrate, and electrically insulated from the second conductive layer by the substrate;

the second conductive layer in electrical contact with the substrate and disposed between the substrate and the base in electrical communication with an earth ground;

wherein the first conductive layer, the substrate and the second conductive layer form a capacitance path between the semiconductor module and the base for reducing circulating currents.

9. The apparatus of claim 8 , wherein the heat sink further comprises:

a body having a surface configured to receive the semiconductor module,

a tub disposed on the surface of the base;

a passageway formed in the base and configured to receive the liquid therethrough; and

wherein a portion of the liquid flows through the passageway is diverted across the tub in thermal communication with the base to transfer heat to the liquid coolant from the semiconductor switch.

10. The apparatus of claim 8 , wherein the semiconductor module is an insulated gate bipolar transistor.

11. The apparatus of claim 8 , wherein the first conductive layer and the second layer are comprised of an electrically conductive metal.

12. The apparatus of claim 11 , wherein the metal is selected from the group consisting of copper, aluminum, gold, silver, platinum and alloys thereof.

13. The apparatus of claim 8 , wherein the second conductive layer is affixed to the base by a solder connection.

14. The apparatus of claim 8 , wherein the substrate comprises a ceramic material.

15. The apparatus of claim 8 , wherein the substrate comprises a nonconductive material.

16. The apparatus of claim 8 , wherein base is connected to earth ground by a conductor.

17. A variable speed drive comprising:

a converter connected to an AC power source, a DC link connected to the converter, and an inverter connected to the DC link, the inverter configured to convert a DC voltage from the DC link into an output AC power having a variable voltage and a variable frequency, the inverter further comprising:

at least one semiconductor module and associated control circuitry mounted on a base;

a nonconductive heat sink in thermal communication with the base and in fluid communication with a source of liquid; and

a grounding assembly comprising;

a first conductive layer capable of being electrically connected to the semiconductor module;

a second conductive layer;

a substrate disposed between the first conductive layer and the second conductive layer, the substrate being electrically connected to the first conductive layer and the second conductive layer; and a base connected to the second conductive layer, the base being electrically connected to earth ground, and the base being electrically connected to the second conductive layer;

the first conductive layer being electrically insulated from the second conductive layer by the substrate; and

wherein the first conductive layer, the substrate and the second conductive layer form a capacitance path between the semiconductor module and the base to reduce circulating currents in the semiconductor module.

18. The system of claim 17 , wherein the semiconductor module is an insulated gate bipolar transistor.

19. The system of claim 17 , wherein the second conductive layer is affixed to the base by a solder connection.