# Heat transfer: does the heat generated in a cable get transferred to the electrical components?

I have a 1000 V, 50 sq mm, double insulated (XLPE) copper conductor cable. This cable is being connected to a power electronic component. The current flowing through it is 230 Amps DC. The cable temperature under steady state operation was found to be 110 °C. Cable insulation max temperature is 150 °C. The temperature range of power electronic component is max 85 °C. The power electronic component also has liquid cooling using Glycol/Water coolant.

What I would like to understand is whether the heat from the high voltage cable will get transferred over to the Power electronic components like Inductors and capacitors? Should I be concerned about my power electronic components getting fried up because of heat transfer from my cable to the electrical components?

To give you a better understanding, I have attached a block diagram of my system.

• Of course it can. Yes you should be concerned. I'd guess the cable-to-component conduction is worse than the component-to-liquid conduction but you know, that does depend on how you built it. Commented Jun 14, 2022 at 9:12
• You could calculate the thermal resistance in between the cable and the cooling system, and from that calculate the temperature of each component. I've seen these calculated with an electrical analogy where heat generators are current sources, thermal resistances are resistors, etc. There's probably FEM solvers out there that give more accurate results for distributed heat sources (like cables and busbars). I'm not an expert in the field of heat transfer. Alternatively, you could build a prototype or scale model and measure it. Commented Jun 14, 2022 at 9:15
• Thank you for your suggestions @user253751 Commented Jun 21, 2022 at 5:16

Most of the heat generated by the cable will be emitted by conduction, radiation and convection to the surroundings like the cable tray and the air.

A tiny bit may get conducted to the board but that will have been considered.

What will cause damage is the heat generated by loose, damaged or poor connections, this can easily burn the component or board.

• Any suggestions on how to consider this quantitatively? Like some references? Big Thanks for your inputs! Commented Jun 13, 2022 at 7:00
• Electrical regs have tables about heating etc of cables, in walls, covered in insulation etc It’s about derating the current carrying capacity. So as not to cause fires. Commented Jun 13, 2022 at 7:32
• That is specific to what amount of current the cable can carry safely (according to various operating temperatures) without affecting the insulation strength. Commented Jun 13, 2022 at 7:38
• When the cable is 110 degrees Celsius (pretty crazy!) and 8mm thick, can you really assume the transfer to the board is "tiny"? Commented Jun 14, 2022 at 9:02
• @user253751 I ran 200m of extension cables to drop about 20 volts at 13A - they ran quite hot (all because the person who made the 380 to 240 transformer messed up the turns ratio. The chief chewed them a new one :) ) But every time I have seen damaged boards then the cause is due to the last phrase in my answer. Commented Jun 14, 2022 at 9:21

... whether the heat from the high voltage cable will get transferred over to the Power electronic components like Inductors and capacitors?

Yes

Should I be concerned about my power electronic components getting fried up...?

Probably not.

You can test whether this is an issue by estimating the thermal resistance from the hot parts of your cable to the various parts you're worried about. Compare this to the thermal resistance from those various parts to whatever cooling you're providing.

Given a good enough knowledge of the thermal resistances and temperatures involved, you can come up with an exact map of the temperature rise of the various components due to cable heating.

Compare that to the temperature rise of those same components due to their normal operation -- then decide whether you need to be concerned.