Rainproof
So constructed, projected, or treated as to prevent
rain from interfering with the successful operation of the apparatus under
specified test conditions.
Rain-tight
So constructed or
protected that exposure to a beating rain will not result in the entrance of
water.
Real Power
Watts.
Reactance
Opposition to the flow
of alternating current. Capacitive reactance is the opposition offered by
capacitor, and inductive reactance is the opposition offered by a coil or
other inductance.
Recloser
The automatic closing of
a circuit-interrupting device following automatic tripping.
Rectifier
An electrical device
used to change AC power into DC power. A battery charger is a rectifier.
Redundancy
The inclusion of
additional assemblies and circuits (as within a UPS) with provision for
automatic switchover from a failing assembly or circuit to its backup
counterpart.
Reflection
The return wave
generated when a traveling wave reaches a load, a source, or a junction
where there is a change in line impedance.
Relay
An electromechanical switching device
that can be used as a remote control.
Reliability
The statistical
probability of trouble-free operation of a given component or assembly. Used
principally as a function of MTBF (Mean Time Before Failure) and MTTR (Mean
Time to Repair).
Resistance
The opposition to the flow of current
caused by the nature and physical dimensions of a conductor.
Resistor
A circuit element whose chief
characteristic is resistance; used to oppose the flow of current.
Rheostat
A variable resistor.
RFI
Radio Frequency Interference.
Ride through
The ability of a
power conditioner to supply output power when input power is lost.
RMS
(Root mean square)- used for
AC voltage and current values. It is the square root of the average of the
squares of all the instantaneous amplitudes occurring during one cycle. RMS
is called the effective value of AC because it is the value of AC voltage or
current that will cause the same amount of head to be produced in a circuit
containing only resistance that would be caused by a DC voltage or current
of the same value. In a pure sine wave the RMS value is equivalent to .707
times the peak value and the peak value is 1.414 times the RMS value. The
normal home wall outlet which supplies 120 volts RMS has a peak voltage of
169.7 volts.
