kashew
Electrical
- Jul 16, 2004
- 10
In the IEEE Buff Book (ANSI/IEEE std 242-1986) more specifically page 94, figure 21 shows the basic formula for calculating parallel impedance.
Z= (R1+jX1)*(R2+jX2)/(R1+jX1)+(R2+jX2)
If you substitute some simple whole numbers for the values such as r=2 and x=2 (for ease of calculation) the resulting impedance is
Z= 1/2 +j1
This illustrates that the resistance value is divided by the number of conductors (in this case 2) and the inductance value of 2 parallel cables is the inductance value of the one cable.
In the Buff Book on the next page 96, however, there appears a contradiction in the example where it shows the inductance value being divided by 2 for a paralleled cable.
I must be missing some basic understanding here. Can anyone explain the difference?
The basic question is: What do you do with the inductance value for paralleled cables?
Z= (R1+jX1)*(R2+jX2)/(R1+jX1)+(R2+jX2)
If you substitute some simple whole numbers for the values such as r=2 and x=2 (for ease of calculation) the resulting impedance is
Z= 1/2 +j1
This illustrates that the resistance value is divided by the number of conductors (in this case 2) and the inductance value of 2 parallel cables is the inductance value of the one cable.
In the Buff Book on the next page 96, however, there appears a contradiction in the example where it shows the inductance value being divided by 2 for a paralleled cable.
I must be missing some basic understanding here. Can anyone explain the difference?
The basic question is: What do you do with the inductance value for paralleled cables?