PCB design with very high amp current ( 60 AMP )

[k.mehta]

Hi,
I am wondering if any one of you have come across very high current carrying power plane in the design. I have a design where the power planes ( 3V3 ) and 5V are going to draw about 60 AMP current. I am using these as power plane with full copper but I believe this will not be enough and the copper thickness will come into play. Can any one tell me 3 oz or 4 oz copper will be good enough to carry 60 amps in power plane. What other precautions I should be looking to avoid any failuare.
I have high spped signal in all inner layers sandwiched between these power planes.]
I hope to get reply from you.
thanks,
keyur

 

[barry]

Look at this, for starters: https://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

I'd also be concerned about large variations in your 60 amp currents, which will induce HORRENDOUS noise on your digital lines.

 

[k.mehta]

Hi Berry, thanks for your quick response. I do use these calculators for my current ratings but I only used upto 4 to 8 Amps max. This is new design challange for me. Since I require 60 amps this is exteremly high current I have bit concern about the heat that will get generated and if I dont get the copper thickness right it may be like an owen once I plugged into the system.
thanks,
keyur

 

[marce]

What is drawing this 60A, as that is a lot for these voltages. Is this a constant 60A or are you working of instantaneous current requirements when devices are switching.
How big is the PCB?

Also use the "Saturn PCB toolkit" it is more up to date with IPC standards on current capacity.

 

[Mattylad]

Why does this current have to flow through the PCB?

The last boards I did that had this sort of current used wiring and shunts etc external to the PCB, only connecting to the PCB where needed using large bolts.

 

[k.mehta]

Hi Mattylan and marce,
thanks for looking into my query. This board is a backplane and is using 19" rack concept with DIN41612 connector concept, it will have 21 off 6U Double Euro card slot insertion into it once in action from both sides. the size of the pcb is 427 X 261 MM.
The current for power supply plane 3V3 and 5V are 60 Amp and 50 Amp respectively. And At the start of the board it will be 60 AMPs max and as you can imagine all the slots drawing current will make it lesser at each connector stage where 6U Card is fitted.
Hope this explains it better.
thanks,
keyur

 

[FvM]

The assumed supply currents also involve 110 A GND return current. I think it's still in the normal range of backplane and power electronic PCBs. I agree with Mattylad, that copper bars routed to multiple press-fit terminals can reduce the PCB current density, but you may prefer PCB-only wiring.

As a first step I would estimate expectable bus resistances and voltage drops for different copper weights and number of planes and calculate the respective voltage drops. I guess, it will rather constrain the design than permitted PCB overtemperatures. Simple rule of thumb, 1 oz corresponds to 0.5 mOhm sheet resistance.

 

[Mattylad]

I think you are going to have to make it clear to others that because of this high current, this is going to take up a lot of space on the board.

Someone will look at it and think - oh you can chuck loads on there, you got bags of room (as they do) lol

Can you use those solder in bus bars for it?