HP Generating Set - Manual (Page 31)

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kW - 1,000 Watts (Real power). Equal to KVA multiplied by the power factor.
POWER - Rate of performing work, or energy per unit of time. Mechanical power is often measured in
horsepower, electrical power in kilowatts.
POWER FACTOR - In AC circuits, the inductances and capacitances may cause the point at which the voltage
wave passes through zero to differ from the point at which the current wave passes through zero. When the
current wave precedes the voltage wave, a leading power factor results, as in the case of a capacitive load or
over excited synchronous motors. When the voltage wave precedes the current wave, a lagging power factor
results. This is generally the case. The power factor expresses the extent to which voltage zero differs from the
current zero. Considering one full cycle to be 360 degrees, the difference between the zero point can then be
expressed as an angle q. Power factor is calculated as the cosine of the q between zero points and is expressed as
a decimal fraction (0.8) or as a percentage (80%). It can also be shown to be the ratio of kW, divided by kVA. In
other words, kW= kVA x P.F.
PRIME POWER - That source of supply of electrical energy utilised by the user which is normally available
continuously day and night, usually supplied by an electric utility company but sometimes by owner generation.
RATED CURRENT - The rated continuous current of a machine or apparatus is the
value of current in RMS or DC amperes which it can carry continuously in normal service without exceeding the
allowable temperature rises.
RATED POWER - The stated or guaranteed net electric output which is obtainable continuously from a
generating set when it is functioning at rated conditions. If the set is equipped with additional power producing
devices, then the stated or guaranteed net electric power must take into consideration that the auxiliaries are
delivering their respective stated or guaranteed net output simultaneously, unless otherwise agreed to.
RATED SPEED - Revolutions per minute at which the set is designed to operate.
RATED VOLTAGE - The rated voltage of an engine generating set is the voltage at which it is designed to
operate.
REACTANCE - The out of phase component of impedance that occurs in circuits containing inductance and/or
capacitance.
REAL POWER - A term used to describe the product of current , voltage and power factor, expressed in kW.
RECTIFIER - A device that converts AC to DC.
ROOT MEAN SQUARE (RMS) - The conventional measurement of alternating current and voltage and
represents a proportional value of the true sine wave.
SINGLE PHASE - An AC load or source of power normally having only two input terminals if a load, or two
output terminals if a source.
STANDBY POWER - An independent reserve source of electrical energy which upon failure or outage of the
normal source, provides electric power of acceptable quality and quantity so that the user's facilities may
continue in satisfactory operation.
STAR CONNECTION - A method of interconnecting the phases of a three phase system to form a
configuration resembling a star ( or the letter Y). A fourth or neutral wire can be connected to the centre point.