Electrical Bus Bar Requirements:
Current Carrying : 300 Amps operating current @ 30°C max temp rise.
Application Dependent Parameters: Minimum Voltage drop, Max Capacitance, Minimum inductance.
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Mechanical and Physical Requirements:
Product Configuration: Two Layer, Rigid Epoxy Glass Board, Edge Potting;
Shape: Planar
Dimensions: 24" long by 1.5" wide max
Materials: Copper alloy 110, Mylar Tedlar Inner Insulation
Termination Method: Threaded Fastener
Mounting Method: Insulated thru holes
Environment: High humidity environment, minimum vibration |
Design Parameter |
Design: Formulas and Tables Used |
Results |
| Cross Sectional Area |
A = 300 x l x [1 + 0.75(N-1)]
formula (2.7)
|
A = 0.097 sq in |
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l = 300 amps
N = 2 layers |
| A = 300 x 300 x [1 + 0.75(2-1)] |
| Conductor Width (w) & Thickness (t) |
w = A / t
formula (2.8) |
t = 0.093"
w = 1.032" |
| |
t = selected thickness values from the available std thickness to get the maximum w / t ratio and practical to the application
A = 0.097 sq in
| Thickness (t) |
0.125" |
0.093" |
0.062" |
| Width (w) |
0.776" |
1.043" |
1.564" |
| w /t Ratio |
6.20 |
11.21 |
25.23 |
The width requirement is 1.5" max therefore 11.21 (0.93"/1.043") is the max w / t ratio practical to the application |
(Optional method)
Use the ampacity table and select the combination of w & t practical to the application and which will yield the lowest inductance (max w / t ratio) |
t = 0.093"
w = 1.040" |
Resistance
|
R = ρ / A ohms/foot
formula (2.1) |
R = 0.084 Milli Ω / foot @ 20°C |
| |
ρ = 8.1 (Ω • sq mil/ft) at Ambient Temp. 20°C
table 3
A = 96,750 sq mil |
| R = 8.1 / 96,750 Ω/foot |
R2 = R1 [1 + α (T2-T1)] ohms/foot
formula (2.2) |
R2 = 1.074 Milli Ω / foot @ 50°C |
| |
R1 = 0.084 Milli Ohms as calculated above
α = .393 from table 3
(T1-T2) = 30°C |
| R2 = 0.084 [(1 + 0.393(30)] |
| Voltage Drop |
ΔV = R x l x l
formula (2.3) |
ΔV = 48 MIlli volts @ 20°C |
| |
l (Conductor length) = 2 ft
R = 0.084 Milli Ohm / foot at ambient temperature
l = 300 Amps |
| ΔV = 0.084 * 2 * 300 = 50.4 Milli Volts at ambient temperature |
| |
R2 = 1.074 Mili Ohm / foot at the 50°C (the max allowed temperature) |
ΔV = 0.644 Volts @ 50°C |
ΔV = 1.074 * 2 * 300
(if this voltage drop is too large, increase cross sectional area) |
| Capacitance |
C = 0.224 (k)(w)(l)/d picofards
formula (2.4) |
C = 0.0095 microfarads |
| |
K (Dielectric constant Mylar tedlar) = 8.5 from table 4
w (width) = 1.040"
l (length) = 24"
d (dielectric thickness) = 0.005" |
| C = (0.224)(8.5)(1.040)(24)/.005 |
| Inductance |
L = 31.9 (l) (d/w) nano Henrys
formula (2.5) |
3.68 nano Henrys |
| |
l = 24"
d = .005
w = 1.040
|
| L = 31.9 (24) (.005/1.040) |
