Series and parallel inductors
When inductors are connected in series, the total inductance is
the sum of the individual inductors' inductances. To understand why
this is so, consider the following: the definitive measure of
inductance is the amount of voltage dropped across an inductor for a
given rate of current change through it. If inductors are connected
together in series (thus sharing the same current, and seeing the
same rate of change in current), then the total voltage dropped as
the result of a change in current will be additive with each
inductor, creating a greater total voltage than either of the
individual inductors alone. Greater voltage for the same rate of
change in current means greater inductance.
Thus, the total inductance for series inductors is more than any
one of the individual inductors' inductances. The formula for
calculating the series total inductance is the same form as for
calculating series resistances:
When inductors are connected in parallel, the total inductance is
less than any one of the parallel inductors' inductances. Again,
remember that the definitive measure of inductance is the amount of
voltage dropped across an inductor for a given rate of current
change through it. Since the current through each parallel inductor
will be a fraction of the total current, and the voltage across each
parallel inductor will be equal, a change in total current will
result in less voltage dropped across the parallel array than for
any one of the inductors considered separately. In other words,
there will be less voltage dropped across parallel inductors for a
given rate of change in current than for any of of those inductors
considered separately, because total current divides among parallel
branches. Less voltage for the same rate of change in current means
less inductance.
Thus, the total inductance is less than any one of the individual
inductors' inductances. The formula for calculating the parallel
total inductance is the same form as for calculating parallel
resistances:
- REVIEW:
- Inductances add in series.
- Inductances diminish in parallel.
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