# RE: [SI-LIST] : Bus bar current carrying capability

Mackillop, William J. ([email protected])
Mon, 22 Jun 1998 08:12:20 -0400

HL Kon,
An application sheet that I have from the Copper
Development Assoc. Inc. gives these formulae and ratings:
I =3D SQRT ((Wr + Wc)/R)
Where Wr is heat dissipated by radiation in Watts
Wc is heat dissipated by natural convection in Watts
R is resistance in Ohms at operating temperature and 60
Hz

DC ampacity differs because of the AC skin effect by
Idc =3D Iac SQRT S
Where S is the skin effect ratio at 60 Hz

For your dimensions the listed attributes are:
DC Resistance (at 20 deg C in microhms per foot) 65.8
30 deg C rise Skin effect ratio 1.01
60 Hz ampacity 240

The assumed conditions are 40 deg C ambient.

All that to say the DC current you could expect is
241Amps.

Hope this helps.

If I understand your problem correctly you need to carry
1000 Amps and therefor should be looking at bus bars in the rage listed
below;
3/16 x 4"
=BC x 3 =BD"
3/8 x 2 =BD"
=BD x 2"

Bill MacKillop=20
804.226.5367 p
804.226.5511 f
[email protected]

-----Original Message-----
From: Kon, Hon Lee
[SMTP:[email protected]]
Sent: Friday, June 19, 1998 5:21 PM
To: [email protected]
Subject: [SI-LIST] : Bus bar
current carrying capability

Hi si-list,
=20
I would be glad if someone could enlighten
me on determining the=20
current carrying capability of a bus bar.
Here is the scenario :
=20
A 10KW(1000Amps @ 10V) power supply will
supply 5V(5KW) to another=20
DC-DC converter using a bus bar. The bus
bar dimension is 0.25" x=20
0.50" (depth x width) and is made of solid
copper with nickel plating.
=20
The dc-dc converter will step down the
output voltage to 1V with=20
maximum output current of 84 Amps. The
power supply will supply=20
5V(5kW) to 12 dc-dc converter along the bus
bar.
=20
Can someone advice me on the limitation of
this system ?
How can I determine the current carrying
capability of this bus bar=20
and how to overcome this limitation ?
=20
Any reply will be greatly appreciated.=20
=20
Thank you very much in advance.
=20
Best regards,
=20
HL Kon
Hardware Development Engineer
Intel Corp.
=20
=20
=20
=20
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