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Ampacities and Mechanical Properties of Rectangular Copper Busbars

Effect of Emissivity and Number of Busses on Ampacity - Data here show how higher emissivities improve ampacity. Multiple busses also affect ampacity in a nonlinear relationship. Ampacity may be raised by increasing heat dissipation through the use of convection cooling or surface treatments. Surface treatments which improve emissivity are available.

Number of
1/4x4 in.
Busses		 Ampacity, Amp
30 °C Rise 50 °C Rise 65 °C Rise
Emissivity Emissivity Emissivity
0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9 0.15 0.4 0.7 0.9
1 1100 1250 1400 1600 1500 1700 1900 2000 1700 1950 2200 2300
2 1900 2050 2200 2300 2550 2750 2950 3100 2950 3200 3400 3600
3 2500 2700 2850 3000 3400 3600 3850 4000 3950 4200 4500 4600
4 3100 3300 3450 3600 4200 4400 4700 4800 4900 5100 5400 5600
* 1/4 in. spacing. Ampacities of bus bar systems of other configurations must be calculated, taking into account size, spacing, number of bus bars and overall skin-effect ratio.

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