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HV-cable dimensioning and cross-section

878 Views 6 Replies 6 Participants Last post by  X19e
I have now scoured the internet for hours looking for a clear answer. I need to dimension the HV lines for our ev conversion, however, I can not find anywhere a clear guideline on how to proceed.
I am using the Hyper9 and SME ACX1 package, so the parameters are as follows:
max peak current (2min): 750 A
system voltage: 125 V
I would like to calculate the cable cross sections for different current and conductor lengths, so what formula would be useful for this?
I am using the HV leads from Huber+Suhner FLR41XC33X
Which further details I need to calculate this?

Thanks, Alex
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Howdy Alex,

How much voltage drop and temperature increase are you willing to accept or required to meet?

What is the duty cycle--2 minutes at 750A, but then what after that?
Let's say, the voltage drop is 0,5V and the temperature increase is 50°C
For the nominal current I only have practice value of 100A.
Lets say the 750A are needed once every 2 minutes for about 6 seconds.
For my project I've used an ampacity chart like this one. This chart was done for a specific voltage on a boat, probably 24V or 48V, so it's not exact for your application in that the voltage drop is likely lower on yours, but it gets the point across of how the chart works. If you want something more accurate, google can find one for 125V.

For 750A (which is pretty massive) you'll probably end up with 4|0 wire no matter what. That level of current also generates some serious EMI spikes, so I would recommend looking at shielded cable and serious grounding points.

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Here's the thing with using a chart: Nissan's Leaf battery puts out over 270A to the inverter, and uses 0 gauge wire. That's because the controller limits the time of peak power and the wire doesn't heat up too much.
The chart above is for continuous current, which is a little harder figure out on a car.
Yeah that's where temperature rise comes into play. Though 50c seems like a lot. Remember that's an increase, so if it's already 30 degrees out, 50 on top of that is getting kind of dangerous imo.
That's the calculator I've used Calculations cable cross-section
It covers all use cases for DC and AC wires. The result is in mm2, but you'll find a converter.
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