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A system and method for cooling power electronics using heat sinks, and including a heat pump. The heat pump includes a main refrigerant circuit having a compressor, an indoor heat exchanger, and an outdoor heat exchanger, and a reversing valve. A biflow expansion valve is configured to receive cond

A system and method for cooling power electronics using heat sinks, and including a heat pump. The heat pump includes a main refrigerant circuit having a compressor, an indoor heat exchanger, and an outdoor heat exchanger, and a reversing valve. A biflow expansion valve is configured to receive condensed liquid refrigerant and to expand the refrigerant. A cooling circuit in fluid communication with the main refrigerant line includes an expansion device configured to receive a portion of condensed liquid refrigerant from the main refrigerant circuit and to expand the portion of condensed liquid refrigerant. A heat sink is configured to receive the expanded portion of refrigerant from the expansion device. Power electronics are coupled to the heat sink such that the portion of expanded refrigerant from the expansion device passes through the heat sink and cools the power electronics.

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1. A heat pump comprising: a main refrigerant circuit including a compressor configured to compress a refrigerant,an indoor heat exchanger,an outdoor heat exchanger,a biflow expansion valve configured to receive condensed liquid refrigerant and to expand the refrigerant, anda reversing valve movable

1. A heat pump comprising: a main refrigerant circuit including a compressor configured to compress a refrigerant,an indoor heat exchanger,an outdoor heat exchanger,a biflow expansion valve configured to receive condensed liquid refrigerant and to expand the refrigerant, anda reversing valve movable between a first position that directs refrigerant from the compressor sequentially to the outdoor heat exchanger, the biflow expansion valve, and the indoor heat exchanger in a cooling mode, and a second position that directs compressed refrigerant from the compressor sequentially to the indoor heat exchanger, the biflow expansion valve, and the outdoor heat exchanger in a heating mode; anda cooling circuit in fluid communication with the main refrigerant circuit, the cooling circuit including a cooling line having a first end and a second end, the first end is at a first branch point on the main refrigerant circuit, the first branch point is between the indoor heat exchanger and the biflow expansion valve, the second end is at a second branch point on the main refrigerant circuit, the second branch point is between the outdoor heat exchanger and the biflow expansion valve,the cooling line further includes a first leg fluidly connected with the first branch point, and a second leg fluidly connected with the second branch point,a first expansion device on the first leg,a second expansion device on the second leg,a heat sink fluidly connected with the first leg and the second leg,the first expansion device, in a heating mode, receives a portion of condensed liquid refrigerant from the main refrigerant circuit, the first expansion device including a first orifice check valve having a first orifice, the first orifice check valve is disposed between the heat sink and the first branch point, the first orifice expands the portion of condensed refrigerant in the heating mode,the second expansion device, in a cooling mode, receives a portion of condensed refrigerant from the main refrigerant circuit, the second expansion device including a second orifice check valve having a second orifice, the second orifice check valve is disposed between the heat sink and the second branch point, the second orifice expands the portion of condensed refrigerant in the cooling mode,the heat sink receives the expanded portion of refrigerant from the first or second expansion device, respectively in the heating or cooling mode, andpower electronics coupled to the heat sink, the portion of expanded refrigerant passing through the heat sink and cooling the power electronics. 2. The heat pump of claim 1, wherein the power electronics are variable frequency drive (VFD) components. 3. The heat pump of claim 2, wherein the compressor is a variable speed compressor and the VFD components control the speed of the compressor. 4. The heat pump of claim 2, further comprising a supply air fan configured to force air through the indoor heat exchanger, the supply air fan driven by a variable speed motor, wherein the VFD components control the speed of the variable speed motor. 5. The heat pump of claim 1, wherein the portion of expanded refrigerant from the heat sink is returned to the main refrigerant circuit downstream of the biflow expansion valve to mix with the refrigerant expanded by the biflow expansion valve. 6. The heat pump of claim 1, wherein the portion of expanded refrigerant from the heat sink is returned to the main refrigerant circuit upstream of the compressor to mix with the refrigerant evaporated by one of the indoor heat exchanger and the outdoor heat exchanger. 7. The heat pump of claim 1, wherein the biflow expansion valve is a thermostatic expansion valve having a 15% bleed. 8. The heat pump of claim 1, wherein the first expansion device of the cooling circuit is a fixed orifice valve, and the second expansion device of the cooling circuit is a fixed orifice valve. 9. A heat pump comprising: a main refrigerant circuit including a compressor configured to compress a refrigerant,an indoor heat exchanger,an outdoor heat exchanger,at least one expansion valve configured to receive condensed liquid refrigerant and to expand the refrigerant,a reversing valve movable between a first position that directs refrigerant from the compressor sequentially to the outdoor heat exchanger, the at least one expansion valve, and the indoor heat exchanger in a cooling mode, and a second position that directs compressed refrigerant from the compressor sequentially to the indoor heat exchanger, the at least one expansion valve, and the outdoor heat exchanger in a heating mode; anda cooling circuit in fluid communication with the main refrigerant circuit, the cooling circuit including a cooling line having a first end and a second end, the first end is at a first branch point on the main refrigerant circuit, the first branch point is between the indoor heat exchanger and the at least one expansion valve, the second end is at a second branch point on the main refrigerant circuit, the second branch point is between the outdoor heat exchanger and the at least one expansion valve,the cooling line further includes a first leg fluidly connected with the first branch point, and a second leg fluidly connected with the second branch point,a first expansion device on the first leg,a second expansion device on the second leg,a heat sink fluidly connected with the first leg and the second leg,the first expansion device, in a heating mode, receives a portion of condensed liquid refrigerant from the main refrigerant circuit, the first expansion device including a first orifice check valve having a first orifice, the first orifice check valve is disposed between the heat sink and the first branch point, the first orifice expands the portion of condensed refrigerant in the heating mode,the second expansion device, in a cooling mode, receives a portion of condensed refrigerant from the main refrigerant circuit, the second expansion device including a second orifice check valve having a second orifice, the second orifice check valve is disposed between the heat sink and the second branch point, the second orifice expands the portion of condensed refrigerant in the cooling modethe heat sink receives the expanded portion of refrigerant from the first or second expansion device, respectively in the heating or cooling mode, andpower electronics coupled to the heat sink, the portion of expanded refrigerant passing through the heat sink and cooling the power electronics. 10. The heat pump of claim 9, wherein the second orifice check valve, in the heating mode, allows substantially unrestricted passage of the portion of expanded refrigerant from the first orifice check valve to the second branch point. 11. The heat pump of claim 9, wherein the main refrigerant circuit includes a suction line between the reversing valve and the compressor, and wherein the cooling circuit further includes a branch line that fluidly connects the heat sink to a third branch point on the suction line, and wherein the second orifice check valve, in the heating mode, inhibits passage of the portion of expanded refrigerant from the first orifice check valve to the second branch point such that the portion of expanded refrigerant is directed to the suction line through the branch line to mix with the refrigerant evaporated in the outdoor heat exchanger. 12. The heat pump of claim 9, wherein the first orifice check valve, in the cooling mode, allows substantially unrestricted passage of the portion of expanded refrigerant from the second orifice check valve to the first branch point. 13. The heat pump of claim 9, wherein the main refrigerant circuit includes a suction line between the reversing valve and the compressor, and wherein the cooling circuit further includes a branch line that fluidly connects the heat sink to a third branch point on the suction line, and wherein the first orifice check valve, in the cooling mode, inhibits passage of the portion of expanded refrigerant from the second orifice check valve to the first branch point such that the portion of expanded refrigerant is directed to the suction line through the branch line to mix with the refrigerant evaporated in the indoor heat exchanger. 14. The heat pump of claim 9, wherein the power electronics are variable frequency drive (VFD) components. 15. The heat pump of claim 14, wherein the compressor is a variable speed compressor and the VFD components control the speed of the compressor. 16. The heat pump of claim 15, wherein each of the first and second orifice check valves includes a fixed orifice valve. 17. The heat pump of claim 14, further comprising a supply air fan configured to force air through the indoor heat exchanger, the supply air fan driven by a variable speed motor, wherein the VFD components control the speed of the variable speed motor. 18. A method of operating a heat pump, the method comprising: directing, in a main refrigerant circuit, compressed refrigerant from a compressor sequentially to an outdoor heat exchanger to condense the refrigerant, at least one expansion valve to expand the refrigerant, and an indoor heat exchanger to evaporate the refrigerant in a cooling mode;directing, in the main refrigerant circuit, compressed refrigerant from the compressor sequentially to the indoor heat exchanger to condense the refrigerant, the at least one expansion valve to expand the refrigerant, and the outdoor heat exchanger to evaporate the refrigerant in a heating mode;directing a portion of the condensed refrigerant, into a cooling circuit, from a point upstream of the at least one expansion valve, with respect to the cooling mode or the heating mode, and toward a heat sink coupled to power electronics;expanding the portion of condensed refrigerant;directing the portion of expanded refrigerant to the heat sink; andcooling the heat sink and the power electronics with the expanded portion of the refrigerant,the cooling circuit is in fluid communication with the main refrigerant circuit, the cooling circuit including a cooling line having a first end and a second end, the first end is at a first branch point on the main refrigerant circuit, the first branch point is between the indoor heat exchanger and the at least one expansion valve, the second end is at a second branch point on the main refrigerant circuit, the second branch point is between the outdoor heat exchanger and the at least one expansion valve,the cooling line further includes a first leg fluidly connected with the first branch point, and a second leg fluidly connected with the second branch point,a first expansion device on the first leg,a second expansion device on the second leg,the heat sink is fluidly connected with the first leg and the second leg,the first expansion device, in the heating mode, receives a portion of condensed liquid refrigerant from the main refrigerant circuit, the first expansion device including a first orifice check valve having a first orifice, the first orifice check valve is disposed between the heat sink and the first branch point, the first orifice expands the portion of condensed refrigerant in the heating mode,the second expansion device, in the cooling mode, receives a portion of condensed refrigerant from the main refrigerant circuit, the second expansion device including a second orifice check valve having a second orifice, the second orifice check valve is disposed between the heat sink and the second branch point, the second orifice expands the portion of condensed refrigerant in the cooling modethe heat sink receives the expanded portion of refrigerant from the first or second expansion device, respectively in the heating or cooling mode, andthe power electronics is coupled to the heat sink, the portion of expanded refrigerant passing through the heat sink and cooling the power electronics.