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9.2. GLOSSARY.
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AC. Alternating current is electric current in which the
magnitude and direction vary cyclically. The waveform of
the most commonly used alternating current is that of a sine
wave, since this achieves a more efficient transmission of
energy. In certain applications, however, other periodic
waveforms are used, such as triangular or square.
•
Bypass. Manual or automatic, this is the physical
connection between the input of an electrical device and
its output.
•
DC. Direct current is the continuous flow of electrons
through a conductor between two points with different
potential. Unlike AC, in DC, electrical loads always circulate
in the same direction from the point of greatest potential
to the lowest. Although DC is commonly identified as a
continuous current (for example, that supplied by a battery),
any current that always maintains the same polarity is
continuous.
•
DSP. Digital signal processor. A DSP is a processor or
microprocessor-based system that has a set of instructions,
hardware and optimised software for applications that
require numerical operations at very high speed. Because
of this, it is especially useful for the processing and
representation of analogue signals in real time: in a system
that works in this way (real time) samples are usually
received from an analogue/digital converter (ADC).
•
Power factor. The power factor, PF, of an AC circuit is
defined as the ratio between active power, P, and apparent
power, S, or as the cosine of the angle formed by the current
and voltage factors, designated in this case as cos f, where
f is the value of the angle.
•
GND. This stands for GROUND or EARTH and, as the name
indicates, refers to the potential of the surface of the Earth.
•
IGBT. An insulated gate bipolar transistor is a semicon-
ductor device that is generally used as a controlled switch
in power electronics circuits. This device possesses the
characteristics of the gate signals of field effect transistors
with the capacity for high current and low saturation voltage
of the bipolar transistor, combining an isolated FET gate for
input and control and a bipolar transistor as a single switch
in a single device. The IGBT’s excitation circuit is similar to
that of the MOSFET, while the conducting characteristics are
similar to those of the BJT.
•
Interface. In electronics, telecommunications and hard-
ware, an interface (electronics) is the port (physical circuit)
through which signals are sent or received from one system
or subsystem to another.
•
kVA. A volt-ampere is the unit used for apparent power in
electrical current. In DC, it is practically equal to real power
but, in AC, it can differ from this depending on the power
factor.
•
LCD. Liquid crystal display, a device invented by Jack
Janning, who was an employee of NCR. It is an electrical
system for data presentation formed by 2 transparent
conductive layers and a special crystalline material in the
middle (liquid crystal) which have the ability to orientate
light as it passes through.
•
LED. Light-emitting diode, a semiconductor device (diode)
that emits light that is almost monochromatic, that is to
say, it has a very narrow spectrum when it is polarised
directly and is penetrated by an electric current. The colour
(wavelength) depends on the semiconductor material
used in the construction of the diode, and can vary from
ultraviolet, passing through the visible light spectrum, to
infrared, the latter called IRED (infra-red emitting diode).
•
Circuit breaker. A circuit breaker is a device capable
of interrupting the electrical current of a circuit when it
exceeds certain maximum values.
•
Disconnector. Mechanical disconnecting device with two
alternative positions with a separation between contacts
that satisfies the minimum physical spacing between the
two parts of the mains where it is located. In case of failure
of the circuit in which it is located, it opens its contacts
automatically, thus isolating the failure. They can open or
close circuits only when they are without loads.
•
On-line mode. A device is said to be on-line when it is
connected to a system, is operative, and normally has its
power supply connected.
•
Inverter. An inverter is a circuit used to convert DC into AC.
The function of an inverter is to change a DC input voltage
to a symmetrical AC output voltage, with the magnitude
and frequency desired by the user or designer.
•
Rectifier. In electronics, a rectifier is the element or circuit
that converts AC into DC. This is done by using rectifier
diodes, whether solid state semiconductors, vacuum
valves or gaseous valves, such as those containing mercury
vapour. Depending on the characteristics of the AC power
that they use, they are classified as single-phase when
they are powered by a mains phase or three-phase when
they are powered by three phases. Depending on the type
of rectification, they can be half wave when only one of the
half cycles of the current is used or full wave when both
half cycles are used.
•
Relay. A relay is an electromechanical device that functions
as a switch controlled by an electrical circuit in which, by
means of an electromagnet, a set of one or several contacts
is activated to enable other independent electrical circuits
to be opened or closed.
•
SCR. Silicon controlled rectifier, commonly known as a
thyristor, a 4-layer semiconductor device that works as an
almost ideal switch.
•
THD. Total harmonic distortion. Harmonic distortion occurs
when the output signal of a system does not equal the
signal that entered it. This lack of linearity affects the
waveform because the device has introduced harmonics
that were not in the input signal. Since they are harmonic,
that is to say, multiples of the input signal, this distortion is
not so dissonant and is less easy to detect.
X-PERT UNINTERRUPTIBLE POWER SUPPLIES (UPS) USER MANUAL