Power converters with immersion cooling

1. A transformer assembly, comprising:

a housing with a sealed housing interior;

a transformer disposed within the housing interior and having:

a magnetic core;

a slotted bobbin seated about the magnetic core and having slot surfaces; and

windings wrapped about the core and having core-facing surfaces, wherein the winding core-facing surfaces and bobbin slot surfaces are spaced apart by a coolant channel; and

a condenser mounted to the housing in fluid communication with the housing interior,

wherein the coolant channel extends along a height of the bobbin between the windings and the condenser to convey coolant of a first phase to the condenser and receive coolant of a second phase from the condenser.

2. The transformer assembly as recited in claim 1 , wherein the coolant channel extends vertically relative to gravity opposite the winding core-facing surfaces.

3. The transformer assembly as recited in claim 1 , wherein the coolant channel is first coolant channel, wherein an interior surface of the housing opposite the an outer winding surface bounds a second coolant passage, wherein the second coolant passage is a downcomer passage.

4. The transformer assembly as recited in claim 1 , further including a coolant disposed within the housing interior and having a boiling temperature that is below a predetermined winding operating temperature.

5. The transformer assembly as recited in claim 4 , wherein a surface of the coolant is separated from the condenser by an ullage space, wherein the windings are immersed in the coolant below the ullage space.

6. The transformer assembly as recited in claim 4 , wherein the coolant has a boiling temperature of about 56 degrees Celsius at a pressure of 1 atmosphere.

7. The transformer assembly as recited in claim 4 , wherein the coolant includes a perfluorohexane-based material.

8. The transformer assembly as recited in claim 1 , wherein the condenser includes a base and fins, wherein the fins extend from the base and towards the windings.

9. The transformer assembly as recited in claim 8 , wherein the fins extend through an ullage space and into a coolant pool disposed within the housing interior.

10. The transformer assembly as recited in claim 8 , wherein the fins include pin fins that define a fluid channel therebetween, the fluid channel extending laterally through the ullage space.

11. The transformer assembly as recited in claim 1 , wherein a width of the bobbin is arranged between the core and the windings.

12. The transformer assembly as recited in claim 11 , wherein the bobbin defines at least one slot containing the coolant channel and extending from a side of the windings opposite the condenser and towards the condenser along the height of the bobbin.

13. The transformer assembly as recited in claim 1 , wherein the windings are inner windings, and further including outer windings wound about the inner windings.

14. The transformer assembly as recited in claim 13 , wherein the coolant channel is an inner coolant channel and further including an outer coolant channel extending between a side of the outer windings opposite the condenser and towards the condenser, the inner coolant channel being bounded by a core-facing surface of the core, the outer coolant channel being bounded by a housing-facing surface of the outer windings.

15. The transformer assembly as recited in claim 1 , wherein the windings include inner windings wrapped about the bobbin and outer windings wrapped about the inner windings, wherein the outer windings housing interior define between one another a downcomer passage, wherein the outer windings and inner windings defined therebetween an upriser passage.