Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

time-to-open contact
a contact in which the desired time to open the contactor could be set by the user.
timer
a circuit that records a time interval.
TOC relay

See time overcurrent relay
tolerance
(1) the total amount by which a quantity is allowed to vary; thus the tolerance is the algebraic difference between the maximum and minimum limits.

In the design of microwave component, it is important to perform a tolerance analysis in order to ascertain if a given component will also satisfy specifications when taking manufacturing tolerances into account.

(2) the amount of error allowable in an approximation.
toroidal deflection yoke
magnetic deflection yoke wound on a toroid core containing a split winding; one-half winding placed on opposite sides of the toroid. The yoke winding interconnection creates an opposing flux from each winding within the toroid and an aiding flux within the toroid inner diameter that causes the deflection of the electron beam. The toroid deflection yoke has a low inductance for compatibility with semiconductor deflection systems and permits precise control of the winding placement to obtain a uniform magnetic deflection field. A horizontal toroidal deflection yoke, in combination with the in-line electron gun, permits the construction of an inherent self-converging color TV display system.
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.
tween
the rotor and rotating magnetic flux of the stator due to increases in shaft load in a synchronous machine.
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.
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