Impedance is the opposition to the flow of
electrons in an AC circuit as a function of the circuit's resistance,
capacitance and inductance. Impedance in an AC circuit is analogous to
resistance in a DC circuit. Even simple wire conductors have properties
of resistance and inductance that affect the impedance of an AC circuit. High
impedance can have a significant impact on power quality in that it
directly affects voltage as a function of the current flow. For
example, a device drawing 1A on a circuit with a 1 ohm impedance and a
100V source will see 99V. If that same device draws 10A, it would see
only 90V. The same device on a circuit with a 0.1 ohm impedance would
see 99.9 and 99V, when drawing 1 and 10A, respectively. A circuit or
system with a low impedance is said to be "stiffer" than its high
impedance counterpart because the voltage changes less as a function of
the current. |