HP Generating Set - Manual (Page 30)

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CURRENT (I) - The rate of flow of electricity. DC flows from negative to positive. AC alternates in direction. The
current flow theory is used conventionally in power and the current direction is positive to negative.
CYCLE - One complete reversal of an alternating current or voltage from zero to a positive maximum to zero to a
negative maximum back to zero. The number of cycles per second is the frequency, expressed in Hertz (Hz).
DECIBEL (dB) - Unit used to define noise level.
DELTA CONNECTION - A three phase connection in which the start of each phase is connected to the end of
the next phase, forming the Greek letter Delta (D). The load lines are connected to the corners of the delta. In
some cases a centre tap is provided on each phase, but more often only on one leg, thus supplying a four wire
output.
DIRECT CURRENT - An electric current which flows in one direction only for a given voltage and electrical
resistance. A direct current is usually constant in magnitude for a given load.
EFFICIENCY - The efficiency of a generating set shall be defined as the ratio of its useful power output to its
total power input expressed as a percentage.
FREQUENCY - The number of complete cycles of an alternating voltage or current per unit of time, usually per
second. The unit for measurement is the Hertz (Hz) equivalent to 1 cycle per second (CPS).
FREQUENCY BAND - The permissible variation from a mean value under steady state conditions.
FREQUENCY DRIFT - Frequency drift is a gradual deviation of the mean governed frequency above or below
the desired frequency under constant load.
FREQUENCY DROOP - The change in frequency between steady state no load and
steady state full load which is a function of the engine and governing systems.
FULL LOAD CURRENT - The full load current of a machine or apparatus is the value of current in RMS or DC
amperes which it carries when delivering its rate output under its rated conditions. Normally, the full load current
is the "rated" current.
GENERATOR - A general name for a device for converting mechanical energy into electrical energy. The
electrical energy may be direct current (DC) or alternating current (AC). An AC generator may be called an
alternator.
HERTZ (Hz) - SEE FREQUENCY.
INDUCTANCE (L) - Any device with iron in the magnetic structure has what amounts to magnetic inertia. This
inertia opposes any change in current. The characteristic of a circuit which causes this magnetic inertia is know
as self inductance; it is measured in Henries and the symbol is "L".
INTERRUPTABLE SERVICE - A plan where by an electric utility, elects to interrupt service to a specific
customer at any time. Special rates are often available to customers under such agreements.
kVA - 1,000 Volt amperes (Apparent power). Equal to kW divided by the power factor.