Glossary – Rockwell Automation 1408-EMxx PowerMonitor 1000 Unit User Manual
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74 PowerMonitor 1000 Unit
Rockwell Automation Publication 1408-IN001E-EN-P - September 2013
Glossary
ampere. A unit of electrical current or rate of flow of electrons. One volt across one ohm of
resistance causes a current flow of one ampere.
apparent power. The product of voltage magnitude and current magnitude in a circuit. Units
are VA or some multiple thereof.
balanced load. An alternating, current power system consisting of more than two current
carrying conductors in which these current-carrying conductors all carry the same current.
baud. A rate at which data transmission occurs, where one baud equals one bit per second.
billing demand. The demand level that a utility uses to calculate the demand charges on the
current month’s bill. Various methods may be used to determine the value, such as minimum
demand, peak demand, or a ratchet clause. It can be based on Watt demand, VA demand, VAR
demand, or some combination of these.
burden. The electrical load placed on source of VA or the load an instrument or meter places on
a current or potential transformer. All current and potential transformers have a rated burden
that should not be exceeded or else transformer transformation accuracy deteriorates.
capacitor. A device consisting essentially of two conducting surfaces separated by an insulating
material or dielectric. A capacitor stores electrical energy, blocks the flow of direct current, and
permits the flow of alternating current to a degree dependent upon the capacitance and
frequency. They may also be used to adjust the power factor in a system.
connected load. The total load that you can impose on the electrical system if everything was
connected at one time. Connected loads can be measured in horsepower, watts or volt-amperes.
Some rate schedules establish a minimum demand charge by imposing a fee per unit of
connected load.
current transformer (CT). A transformer, intended for measuring or control purposes, designed
to have its primary winding connected in series with a conductor carrying the current to be
measured or controlled. CT’s step down high currents to lower values that can be used by
measuring instruments.
current transformer ratio. The ratio of primary amperes divided by secondary amperes.
data table. The power monitor data is organized in data tables similar to those found in an
SLC 5/03 programmable controller. The detailed data-table definitions are covered in the
PowerMonitor 1000 Communication Reference Manual, publicatio
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.
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.
inductor. A device consisting of one or more windings with or without a magnetic core. Motors
are largely inductive.