Substation1
Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

AC/AC converter
a power electronics device in which an AC input voltage of some magnitude, frequency, and number of phases is changed to an AC output with changes to any of the previously mentioned parameters.

AC/AC converters usually rectify the input source to a DC voltage and then invert the DC voltage to the desired AC voltage.
AC/DC converter

See rectifier
amortisseur winding

See damper winding
antiparticle
a particle having the same mass as a given fundamental particle, but whose other properties, while having the same magnitude, may be of opposite sign. Each particle has a partner called an antiparticle. For example, electrical charge in the case of the electron and positron, magnetic moment in the case of the neutron and antineutron. On collision a particle and its antiparticle may mutually annihilate with the emission of radiation. Some properties of the antiparticle will be identical in magnitude but opposite in sign to the particle it is paired with.
aperture
(1) an opening to a cavity, or wave-guide, from which radiation is either received or transmitted. Typically used as antenna or a coupling element.
(2) a physical space available for beam to occupy in a device. Aperture limitations are the physical size of the vacuum chamber; a magnetic field anomaly may deflect the beam so that the full available aperture cannot be used.
aperture antenna
an antenna with a physical opening, hole, or slit.
artificial dielectric
a dielectric material that has been modified to alter its properties. Common modifications include micro-machining to remove material from the substrate under planar patch antenna to improve radiation properties and the fabrication of periodic arrays of holes to realize guiding or photonic bandgap structures.
artificial intelligence
the study of computer techniques that emulate aspects of human intelligence, such as speech recognition, logical inference, and ability to reason from partial information.
autotransformer starter
a single three-phase autotransformer or three single phase transformer used to start induction motors at a reduced voltage.
beta particle
an electron or positron emitted from a radioactive source.
black start
the task of re-starting an isolated power system which is completely de-energized. Most generating plants require substantial external electric power to start. Thus a black start may be initiated by hand-starting gas turbine generators or by opening the gates of a hydroelectric generator somewhere in the system.
capacitor-start induction motor (CSIM)
a single-phase induction motor with a capacitor in series with its auxiliary winding, producing nearly a 90. phase difference between the main winding and the auxiliary winding currents at starting. This results in a high starting torque, so this motor is used for hard-to-start loads. The auxiliary winding and capacitor are removed from the circuit by a centrifugal switch as the machine approaches operating speed.
converter
a generic term used in the area of power electronics to describe a rectifier, inverter, or other power electronic device that transforms electrical power from one frequency and voltage to another.
counter-EMF starter
a type of DC-motor starter that reduces the resistance in the starting circuit as the voltage across the armature rises.
DC-AC inverter

See inverter
DC-DC converter
a switching circuit that converts direct current (DC) of one voltage level to direct current (DC) of another voltage level. A typical DC-DC converter includes switches, a low pass filter (to attenuate the switching frequency ripple), and a load. The size of magnetic components and capacitors can be reduced and bandwidth can be increased when operating at high frequency. Most DC-DC converters are pulse-width modulated (PWM), while resonant or quasi-resonant types are found in some applications. Commonly used topologies include the buck converter, boost converter, buck-boost converter, and Cuk converter. Isolation can be achieved by insertion of a high frequency transformer.
direct converter
a frequency converter that converts an RF signal to a baseband signal directly in receivers. It converts a baseband signal to an RF signal directly in transmitters.
direct-axis subtransient short-circuit time constant
a constant that characterizes the initial decay of transients in the d-axis variables of the synchronous machine with the stator windings short-circuited. The interval characterized is that immediately following a disturbance, during which the effects of amortisseur windings are considered. A detailed (derived) closed-form expression for the subtransient short-circuit time constant of a machine with a single d-axis amortisseur winding is obtained by taking the reciprocal of the largest root of the numerator of the d-axis operational impedance. An approximate (standard) value is often used, in which it is assumed the field winding resistance is small and the detailed expression simplified.
direct-axis transient short-circuit time constant
a constant that characterizes the decay of transients in the d-axis variables of the synchronous machine with the stator windings short-circuited. The interval characterized is that following the subtransient interval, but prior to steady-state, in which the effects of the amortisseur windings are small (possibly negligible). A detailed (derived) closed-form expression for the short-circuit transient time constant is obtained by taking the reciprocal of the smallest root of the numerator of the d-axis operational impedance. An approximate (standard) value is often used, in which it is assumed the amortisseur winding resistance is infinite and the detailed expression simplified.
earth electrode system
a network of electrically interconnected rods, plates, mats, or grids installed for the purpose of establishing a low-resistance contact with earth. The design objective for resistance to earth of this subsystem should not exceed 10 Ω.