Rockwell Automation 1426 PowerMonitor 5000 Unit - Manual (Page 384)

384 Rockwell Automation Publication 1426-UM001F-EN-P - November 2013
Glossary
Demand Hours The equivalent number of hours in a month during which the peak demand is
fully utilized. In other words, if energy consumption for the current month is X
kwhr and the peak demand is Y kW, then the demand hours is equal to X/Y
hours. The higher the number of demand hours, the better the demand leveling
situation, and the more effectively demand is being used.
Demand Interval Demand charges are based on peak demand over a utility specified time interval,
not on the instantaneous demand (or connected load) at any given moment.
Typical demand intervals are 15, 20, and 30 minutes.
Frequency The number of recurrences of a periodic phenomenon in a unit of time. In
electrical terms, frequency is specified as so many Hertz (Hz) where one Hz
equals one cycle per second.
Horsepower (hp) A unit of power, or the capacity of a mechanism to do work. It is equivalent to
raising 33,000 pounds one foot in one minute. One horsepower equals 746 watts.
Impedance The total opposition (that is, resistance and reactance) a circuit offers to the flow
of alternating current at a given frequency. It is measured in ohms.
Induction Motor An alternating current motor in which the primary winding (usually the stator) is
connected to the power source and induces a current into a secondary (usually
the rotor).
Inductor A device consisting of one or more windings with or without a magnetic core.
Motors are largely inductive.
Initiator Pulses Electrical impulses generated by pulse-initiator mechanisms installed in utility
revenue meters. Each pulse indicates the consumption of a specific number of
watts. These pulses can be used to measure energy consumption and demand.
Lagging Current The current flowing in an AC circuit that is mostly inductive. If a circuit contains
only inductance, the current lags the applied voltage by 90°. Lagging current
means lagging power.
Leading Current The current flowing in a circuit that is mostly capacitive. If a circuit contains only
capacitance, the current leads the applied voltage by 90°. Leading current means
leading power factor.
Load Any device or circuit consuming power in an electrical system.
Load Shedding The removal of load from the line to limit load and control demand level.
Load Restoring The energizing of loads that were previously removed from the line to limit load
and control demand level.