Page 199 - Intro Predictive Maintenance

190 An Introduction to Predictive Maintenance

monic distortion. This can cause overheat-
ing of circuit elements and might appear to
a device as data-corrupting noise.

Hertz (Hz) A term describing the frequency of alter-
nating current. The term hertz is synony-
mous with cycles per second.
Impedance (Z) Measured in ohms, impedance is the total
opposition to current flow in a circuit in
which alternating current is flowing. This
includes inductive reactance, capacitive
reactance, and resistance.
Inductance This term describes the electrical properties
of a coil of wire and its resultant magnetic
field when an alternating current is passed
through it. This interaction offers imped-
ance to current flow, thereby causing the
current waveform to lag behind the voltage
waveform. This results in what’s known as
a lagging power factor.

Inductor A discrete circuit element, which has the
property of inductance. It should be noted
that at very high radio frequencies, a
straight wire or a path on a printed-circuit
board can act as an inductor.
Insulator A nonconducting substance or body, such
as porcelain, glass, or Bakelite, that is used
for insulating wires in electrical circuits to
prevent the undesired flow of electricity.
Inverter An inverter takes DC power and converts
it into AC power.
Isolation The degree to which a device can separate
the electrical environment of its input from
its output, while allowing the desired trans-
mission to pass across the separation.
Kilohertz (kHz) A term meaning 1,000 cycles per second
(cps).
Kilovolt-Ampere (kVA) An electrical unit related to the power
rating of a piece of equipment. It is cal-
culated by multiplying the rated voltage of
equipment by the current required (or
produced). For resistive loads, 1 kilovolt-
ampere equals 1 kilowatt.