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Commonly used terms in the Electrical industry.
transient operation
a power system operating under abnormal conditions because of a disturbance.
transient reactance
the reactance offered for the transient currents in synchronous machines. Referred to by the symbol X
s
, the transient reactance is a function of the stator frequency and the transient inductance. X
s
is comparatively smaller in comparison to the steady-state inductive reactance of the machine.
transient short-circuit
time constant pass and stop bands are critical. A longer filter length generally implies that the filter can have a steeper transition band to a similarly shaped shorter length filter.
transient stability
the ability of a power system to remain stable following a system disturbance.
transient suppressor
a device connected to a piece of sensitive electrical equipment to reduce the amplitude of transient voltage excursions, thus protecting the equipment.
transmission line
(1) an arrangement of two or more conductors used to convey electromagnetic energy from one point to another.
(2) conductive connections that guide signal power between circuit elements.
transmission line coupler
passive coupler composed of two or more transmissions spaced closely together where the proximity of the transmission lines allows signals to be coupled or transferred in part from one line to the other. The electrical length of the transmission lines is usually one quarter of a wavelength.
transmission line filter
a microwave device that is made up of sections of transmission lines so as to act as a filter in the microwave frequency range.
transposition
(1) the practice of twisting a three-phase power line so that, for example, phase A takes the place on the tower formerly occupied by phase B, phase B takes the place of phase C, and phase C occupies the former position of phase A.
(2) a point on a three-phase electric power line where the conductors are physically transposed for purposes of improving circuit balance transputer a class of CPU designed and manufactured by Inmos Corporation. The transputer was specifically designed to be used in arrays for parallel processing.
triac
a power switch that is functionally a pair of converter-grade thyristors connected in anti-parallel. Triacs are mainly used in phase control applications such as dimmer switches for lighting. Because of the integration, the triac has poor reapplied dv=dt, poor gate current sensitivity at turn-on, and longer turn-on time. They are primarily used for AC power control with resistive loads, such as in light dimmers.
triplex cable
a cable used for residential or commercial service drops consisting of two or three insulated conductors spiralled around a bare neutral wire which provides support for the cable.
turbogenerator
a generator driven by a steam-turbine engine.
turns ratio
the ratio of the number of turns between two coupled windings, e.g., for a transformer, it is the ratio of number of turns of the primary winding to the number of turns of the secondary windings. For an induction machine, it is the ratio of the number of turns of the stator winding to the number of turns of the rotor winding.
twelve-pulse converter
the combination of two 6-pulse converters connected through a Y-Y and a delta-Y transformer in order to cancel the characteristic 5th and 7th harmonics of the 6-pulse converters. The lowest characteristic harmonics with twelve-pulse converters under balanced conditions are the 11th and 13th harmonics. The converters are connected in parallel on the AC side and in either series or parallel on the DC side, depending on the required DC output voltage.
two-lamp synchronizing
the process to connect two three-phase power systems in parallel using the same procedure as for three-lamp synchronizing except that lamps are placed across only two phases of the switch. See also three-lamp synchronizing.
ultra-high frequency (UHF)
electromagnetic spectrum with frequencies between 300 MHz and 3000 MHz or wavelengths between 10 cm and 100 cm. Also called as decimetric waves.
ultrasound
an imaging modality that uses reflected high-frequency sound energy to image the interface between materials with different acoustic impedances.
ultraviolet
a term referring to wavelengths shorter than 400 nm, but longer than 30 nm. The region 400-300 nm is the near ultraviolet, 300-200 is the middle ultraviolet; and 200-30 nm is the far ultraviolet or vacuum.
ultraviolet laser
laser producing its output in the ultraviolet region of the spectrum.
unbalanced magnetic pull
a phenomenon in electric machines arising from the rotor not being symmetrical with respect to the stator or the axis of the rotor and stator not being coincident. Results in a higher pulling force on the side with the smaller airgap, resulting in additional bearing stresses.