Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

torque
the product of a force acting at a total harmonic distortion (THD) an in-distance. The output of an electric motor. dex that quantifies the amount of distortion in the voltage or current waveform with respect torque angle the displacement angle be-to the fundamental component.
torque pulsation
oscillating torque produced by the interaction between the air gap flux, consisting mainly of the fundamental component, and the fluxes produced by harmonics in the rotor. Torque pulsations can stimulate complex mechanical vibrations that can flex and damage rotor and turbine elements.
torque ripple
in variable speed motor drives, refers to the torque not being smooth as the rotor moves from one position to another. Torque ripple may be produced from space harmonics within the machine or time harmonics generated by the supply.
torque servo
a servo where the output torque is the controlled variable and the operating speed depends on the load torque.
See servo
torus
a donut-shaped magnetic core used in electric transformers.
total harmonic distortion
disturbance level an electromagnetic disturbance level due to all emissions from equipment in a system.

This is expressed as a ratio of the RMS value of the harmonic content to the RMS of the fundamental and is calculated as a percentage of the fundamental component.
tower
a structure for elevating electric transmission lines, distinguished from a pole cf by its greater height and structural complexity.
trace length
the physical distance between electronic components connected by a circuit path.
transducer
a device that converts a physical quantity into an electrical signal. Typically, transducers are electromechanical energy conversion devices used for measurement or control. Transducers generally operate under linear input-output conditions and with relatively small signals. Examples include microphones, pickups, and loudspeakers.
transducer gain
ratio of the power delivered to the load to the power available from the source.
transformation ratio
dimensionless ratio of the real parts of the load and source impedance.
transformed circuit
an original circuit with the currents, voltages, sources, and passive elements replaced by transformed equivalents.
transformer
a device that has two or more coils wound on an iron core. Transformers provide an efficient means of changing voltage and current levels, and make the bulk power transmission system practical. The transformer primary is the winding that accepts power, and the transformer secondary is the winding that delivers power. The primary to secondary voltages are related by the turns ratio of the coils. The corresponding currents are related inversely by the same ratio.
transformer differential relay
a differential relay specifically designed to protect transformers. In particular, transformer differential relays must deal with current transformer turns ratio error and transformer inrush and excitation current.
transformer fuse
a fuse employed to isolate a transformer from the power system in the event of a transformer fault or heavy overload.
transformer vault
a fireproof enclosure in which power transformers containing oil must be mounted if used underground or indoors.
transient
(1) the behavior exhibited by a linear system that is operating in steady state in moving from one steady state to another. For stable systems, the transient will decay while for unstable system it will not, and thus the latter never reach another steady-state operation. See also settling time and time constant.

(2) any signal or condition that exists only for a short time.

(3) an electrical disturbance, usually on a power line.

(4) refers to momentary overvoltages or voltage reductions in an electric power system due to lightning, line switching, motor starting, and other temporary phenomena.
transient current
the fault current that flows during the transient period when the machine apparent impedance is the transient impedance.
transient fault
a fault that can appear (e.g., caused by electrical noise) and disappear within some short period of time.
transient impedance
the series impedance that a generator or motor exhibits following the subtransient period but prior to the steady-state situation.
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