Something we developing for a client. Toroidal transformers notoriously hard to cool, they are well isolated.
So we designing and making custom 250A TX using integrated heatpipes. Idea is to remove heat directly from the core of the TX and move it to external heatsink. There are two heatpipes at the moment, each capable to move 300W of heat.

 

Heat pipes on the outer surface of the toroid core will certainly be able to remove some amount of heat, but there is still the inner portion of the winding without a direct contact with the heat removal system.
How much power is to be lost in this toroid transformer that this much cooling will be needed? It might be cheaper to improve the efficiency. Or has that already been examined.??

 

I had one customer wonder why his toroidal transformer was overheating with no load connected, Found he had a securing strap that went from the Centre bolt back to chassis.
Essentially creating a shorted turn!

 

What is the torrid made of? Seems like there is too much eddie current losses in the material or there is a short.

 

I had one customer wonder why his toroidal transformer was overheating with no load connected, Found he had a securing strap that went from the Centre bolt back to chassis.
Essentially creating a shorted turn!

LOL classic

 

Heat pipes on the outer surface of the toroid core will certainly be able to remove some amount of heat, but there is still the inner portion of the winding without a direct contact with the heat removal system.
How much power is to be lost in thistoroid transformer that this much cooling will be needed? It might be cheaper to improve the efficiency. Or has that already been examined.??

Application is demanding industrial powersupply. High ambient temperature (enclosure under the sun), compact space. Require high reliability. We have no say in post TX electronics and drive circuitry We are already at Class "H"
We tried going to high grade steel core and optimizing windings. But there is only so much you can do without going to larger TX. Larger mean more space needed also higher inrush that brings it's own issues.
Competitors in EV charging sector use to mount TX on 'cool plate' with coolant circulated. But this only remove heat on one side of TX, and externally.

 

What is the torrid made of? Seems like there is too much eddie current losses in the material or there is a short.

Client's drive circuit is tough. Phase control on secondary, at full current output we can see sine wave cut to over 70% in some applications. It is the case on undersized TX been abused. But they have own reasons.
Ideally, they need to control primary.

 

OK, now it makes some sense. In some instances initial cost is the main driver, with efficiency, effectiveness, and durability coming in a distant last. So the client is obviously NOT NASA or the military.
Embedded heat pipes is an interesting scheme indeed.
Probably vacuum impregnating with a selected heat conductive material will be useful as well. GOOD LUCK!!!
EV chargers with the water-cooled connecting cable do seem rather poorly thought out, because every watt spent as heat is wasted power. Evidently the marketing people are doing the design work.