Inductance of Power Supply Wiring
7.3 Inductance of Power Supply WiringThe inductance of the power supply wiring can be calculated using the formula
L = 10.16 X ln(2H/D) [7.5]
where,
X = length of wire in inches
H = average separation between the wires
D = Wire diameter
L = inductance in nH
Note that the inductance is a logarithmic function of the diameter. Doubling the wire diameter will not halve the inductance. It reduces the inductance only slightly. The following example illustrates it.
Example 7.3 - Find the inductance of 5 inches of a wire with wire diameter of 0.06 inch and average separation between the positive and ground connection to be 0.15 inch. Find the diameter of the wire if the inductance needs to be reduced to one third.
Solution – Using the formula
L = 10.16 X ln(2H/D),
Here X = 5 inches
H = 0.15 inches
D = 0.06 inch
This gives,
L = 81.75 nH
Again looking at the formula
L = 10.16 X ln(2H/D),
We get
D = 2H/ eL/(10.16X)
Substituting the values
L = 27.25 nH,
H = 0.15 in
X = 5 in
We get D = 0.133 inches
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