Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

pull-out torque
the maximum value of torque that an AC motor can deliver. An induction motor operating at the pull-out torque will operate at maximum slip, and loading it beyond the pull-out torque will cause the motor to stall. Synchronous motors remain at synchronous speed up to the pull-out torque. Exceeding the pull-out torque for a synchronous machine will lead to pole slipping and destruction of the machine.
pull-up torque
the minimum torque generated by an AC motor as the rotor accelerates from rest to the speed of breakdown torque. For an induction motor, this value usually is less than the locked-rotor torque, and thus establishes the maximum load that can be started.
pulse
a sudden change of an electrical value of short duration with a quick return to the original value. A pulse injects a short sharp burst of energy into a system and is usually quantified by its area rather than its amplitude or its duration. In the limit as the amplitude tends to infinity and the duration to zero, it approaches the Dirac delta function whose Laplace transform is unity.
q
unit of electric charge. q = 1.602 x 10-19 coulombs.
Q-factor
a figure of merit that represents the ratio of stored to dissipated energy per cycle.
RS
commonly used symbol for source impedance.
RT
commonly used symbol for transformation ratio.
RL
Typical symbol for load resistance.
raceway
a channel within a building which holds bare or insulated conductors.
radial intensity histogram
a histogram of average intensities for a round object in circular bands centered at the center of the object, with radial distance as the running index. Such histograms are easily constructed, and, suitably normalised, form the basis for scrutinizing round objects for defects, and for measuring radius and radial distances of cylindrically symmetrical features.
radial system
a network of straight wires or other conductors radiating from the base of a vertical monopole antenna that simulates the presence of a highly conducting ground plane beneath the antenna. Typically, radial wires are approximately a quarter wavelength long and are arranged to have equiangular spacing between them. The radial wire ends at the base of the monopole are electrically bonded together and to one conductor of the feedline.
rare-earth magnet
a magnet that has any of the rare-earth elements in its composition. Typically stronger than other magnet materials, these include neodymium iron boron and samarium cobalt.
rare-earth permanent magnet
magnet made of compounds of iron, nickel, and cobalt with one or more of the rare-earth elements such as samarium. These materials combine the high residual flux density of the alnico-type materials with greater coercivity than ferrites.
rated voltage
the voltage at which a power line or electrical equipment is designed to operate.
reactance grounded
an electrical system in which the neutral is intentionally grounded through a reactance. Frequently used in the neutral of generators and transformers to limit the magnitude of line to ground fault currents.
reactive compensation
process of counteracting the reactive component of a device by means of capacitors and inductors. Both series and shunt compensation are prevalent.
reactive load
a load that is purely capacitive or inductive.
reactive power
(1) electrical energy per unit time that is alternately stored, then released. For example, reactive power is associated with a capacitor charging and discharging as it operates on an AC system. Symbolized by Q, with units of volt-amperes reactive (VAR), it is the imaginary part of the complex power.

(2) the power consumed by the reactive part of the load impedance, calculated by multiplying the line current by the voltage across the reactive portion of the load. The units are vars (volt-ampere reactive) or kilovars.
reactor
a container where the nuclear reaction takes place. The reactor converts the nuclear energy to heat.
real power
consider an AC source connected at a pair of terminals to an otherwise isolated network. The real power, equal to the average power, is the power dissipated by the source in the network.
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