Inductor mathematics (DC)

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How the inductor works

Inductor family

Inductor color code

Series and parallel circuits

Calculating time constant

Making Circuit boards

Introduction

Here you will find how to calculate time constants for DC circuits and see the affects they have on electricity.
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Time constants

Click here for notation table
Calculator

   The first step in calculating what the inductor will do on a circuit and how much time it will do it in is quite simple once you understand the mechanics. First what you will need to do is calculate the time it will take to complete a Time constant. To figure the time constant you will need to divide the inductance by the resistance in the circuit.
   Lets say that we have a circuit with an inductance of .0025Henries and a resistance of 10k ohms, the equation for finding the length per time constant would be as follows:

   .0025H ÷ 10,000 Ohms = .00000025 or 230 nano seconds.

Calculating time constants

   You got the amount of time it will take to reach one full time constant out of 5 but now you will need to find the affects on the circuit. To do that you will need to follow the equation table below.
   The first time constant will allow 63.2% of the current to travel, the rest of the 36.8% of the current is resisted due to the inductance.
   Since we can find a percentage by subtracting two placeholders "move decimal point two places to the right" and multiplying the original number, things will go a little faster.
   Let us say that there is an input of 32.25A, the equation would be as follows:

Calculator

Time
sonstant 1

Time
sonstant 2

Time
sonstant 3

Time
sonstant 4

Time sonstant 5

32.25A * .632 = 20.38

32.25 - 20.38 = 11.87

11.87 * .632 = 7.5

20.38 + 7.5 = 27.88

32.25 - 27.88 = 4.37

4.37 * .632 = 2.76

2.76 + 27.88 = 30.64

32.25 - 30.64 = 1.61

1.16 * .632 = 0.73

.73 + 30.64 = 31.37

32.25 - 31.37 = 0.88

0.88 * .632 = .55

.55 + 31.37 = 31.92

Find 63.2% of introductory current
Subtract answer form original current

   Find 63.2% of remaining current
   Add current sum to previous time constant sums
   Calculate remaining current for next time constant

   Find 63.2% of remaining current
   Add current sum to previous time constant sum
   Calculate remaining current for next time constant

Find 63.2% of remaining current
Add current sum to previous time constant sum

DC calculations

   The graph above is a depiction of what happens when current is introduced into a circuit with an inductor.
   Notice that time goes from left to right while the timeline is broken up into five time constants.
   Each time constant TC1, TC2, TC3, etc, is determined by the equation at the top of this page labeled Time constants.
   In this case each time constant is 230 nano seconds per time constant, multiply this time by 5 "because 5 time constants", and you will reach the end of the inductors use within a DC circuit.
   Since the inductors main purpose is to introduce a special kind of resistance within a circuit "mainly power supplies" you need to look at in an AC circuit because that is mainly what they are designed for which is in the next page.

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