Inverter for an electric motor

• US 6,529,394 B1
• Filed: 11/07/2000
• Issued: 03/04/2003
• Est. Priority Date: 11/07/2000
• Status: Expired due to Fees

• Current Assignee: United Defense LP (BAE Systems Plc)
• Original Assignee: United Defense LP (BAE Systems Plc)
• Inventors: Joseph, Craig, Arnold, Kelly W.
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US09/708,182
• Time in Patent Office: 847 Days
• Field of Search: 363/141, 363/147, 363/144, 363/145, 361/689, 361/699, 361/704, 361/707, 361/710, 165/80.6
• US Class Current: 363/141
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H05K 7/20927 Liquid coolant without phase change

Abstract

An oil-cooled inverter for an electric traction motor that uses six IGBT switches to generate 3-phase AC electrical current as its output. The switches are mounted on heat sinks that use hot motor oil (hydraulic fluid) as the heat transfer fluid. An interior of each of the heat sinks contains a heat transfer medium. The heat sink housing is made of molybdenum, which has a thermal expansion rate equal to that of silicon. This allows the circuitry of the inverter to be mounted directly on the top surface of the heat sinks, as the expansion and contraction of the heat sink housing will match that of the silicon substrate of the chips. Since both elements, the heat sink housing and the chip substrate, expand and contract at an equal rate during heating and cooling, the problem of the chip substrate cracking and breaking due to thermal flexing is eliminated. The inverter is in most ways electrically equivalent to prior art inverters, but the upper surface formed by the bank of heat sinks is electrically hot, and is used as part of the inverter circuitry. This allows the elimination of the insulating plate on which the inverter circuitry is normally mounted, as the chips of the inverter circuitry are mounted directly on the upper surface of the heat sinks of the inverter.

Claims

1. An inverter for an electric motor comprising:

a switching means,

a heat sink means associated with said switching means,

a capacitance means, and

DC to AC inverter circuitry;

wherein

said switching means and said DC to AC inverter circuitry enable said inverter to receive DC voltage as an input and to output 3-phase AC current,

chips of said inverter circuitry and said switching means are mounted directly on a top surface of said heat sink means, and

said heat sink means comprises a housing with at least one heat transfer liquid throughway in an interior of said heat sink housing,

at least an input and an outlet port for heat transfer liquid, such that said heat transfer liquid flows through said heat sink means to dissipate heat from said switching means, and

an interior heat transfer medium, said heat transfer medium comprising a plurality of metallic spheres thermally connected to each other and to an interior surface of said heat sink housing, such that a spaced lattice structure is formed.

2. The inverter of claim 1 wherein:

said heat sink means is installed in line with an oil cooling system of a motor utilizing said inverter.

3. The inverter of claim 1 wherein:

said metallic spheres are silver plated copper balls.

4. The inverter of claim 1 wherein:

said heat transfer liquid throughway comprises a pair of parallel channels, each said channel having an open portion on an upper inner side thereof, such that said heat transfer liquid fills said channels and spills into an interior of said heat sink means, thereby surrounding a heat transfer medium contained in an interior of said heat sink means.

5. The inverter of claim 1 wherein:

said heat sink means is constructed with a flat elongated geometry.

6. The inverter of claim 1 wherein:

said switching means, said heat sink means, said capacitance means, and said DC to AC inverter circuitry are installed in a bus structure, said bus structure securing said switching means, said heat sink means, said capacitance means, and said DC to AC inverter circuitry in a flat elongated conformation such that inductance of said inverter is decreased.

7. The inverter of claim 1 wherein:

said switching means comprises six switches, each said switch being mounted on an independent heat sink means element.

8. The inverter of claim 7 wherein:

said heat sink means elements are aligned in two rows, each said row including three of said heat sink means elements.

9. The inverter of claim 8 wherein:

each of said heat sink means elements in each said row is in communication with an adjacent heat sink means element, such that liquid can flow from a first heat sink means element in a row, through a second heat sink means element in said row, and through a third heat sink means element in said row.