Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

pickup current
the specified value that, if exceeded, causes the relay to act on its contact and cause a circuit breaker action. It is the threshold current for system protection, and a magnitude above this is considered a fault or abnormal condition.
pickup voltage

See pickup current
pig tail
a type of hot stick that can slide over an overhead conductor.
pigtail
short electrical conductor used to connect the brushes of an electrical motor or generator to the external electrical connections of the machine.
pilot carrier
a means of providing a carrier at the receiver, which matches the received carrier in phase and frequency. In this method, which is employed in suppressed carrier modulation systems, a carrier of very small amplitude is inserted into the modulated signal prior to transmission, extracted and amplified in the receiver, and then employed as a matching carrier for coherent detection.
pin insulator
an electric insulator which is concentric with a hollow, threaded hole so that it can be screwed onto a steel pin mounted on a utility pole or crossarm.
pipe cable
a paper-insulated high-voltage electric power transmission cable laid within a rigid steel pipe containing pressurized insulating oil.
pitch factor
in an electric machine, the ratio of the fractional pitch in electrical degrees to the full pitch, also in electrical degrees.
polarity
the notation used in the assignment of voltages. In DC generators, the polarity of the armature voltage can be reversed by either reversing its field current or by rotating the generator in reverse direction.
polarization
(1) the shape traced out by the tip of the electric field vector as a function of time and the sense in which it is shaped.

(2) a description of the form of the temporal variation of the electric field vector of a light field. In general, the polarization state can be described by the ellipse that tip of the electric field vector traces each optical cycle.
Commonly encountered limiting forms are linear polarization and circular polarization.

(3) the response of material systems, an applied light field by developing a time varying dipole moment. The response is described quantitatively in terms of the dipole moment per unit volume, which is known as the polarization vector.

(4) description of the direction and motion of the electric field vector of a wave. Plane waves may be linearly or elliptically (including circularly) polarized. polarization controller a device that alters only the polarization state of the incident light.
pole
one end of a magnet or electromagnet in electrical machines, created by the flux of the machine.
pole line
any power line which is carried overhead on utility poles.
pole pitch
the angular distance (normally in electrical degrees) between the axes of two poles in an electrical machine.
pole top pin
a steel pin onto which a pin insulator is screwed.
pole-top transformer
generally a distribution transformer which is mounted atop a utility pole near the customer.
polyphase system
electrical system that has more than one phase, which are separated by angles of 360=n, where n is the number of phases. For example, three phase systems are polyphase systems where the three phases are separated by 120 electrical degrees from each other. A six-phase system is a polyphase system where each successive phase is separated by 60 electrical degrees from the other.
position sensor
a device used to detect the position of the rotor with respect to the stator. The most commonly used position sensors for electric motors are Hall effect devices, encoders, and resolvers with resolver-to-digital converters.
position servo
a servo where mechanical shaft position is the controlled parameter.
See servo
positioner
a mechanical device used to move an antenna or target to a desired position for measurement purposes. Positioners can be single or multi-axis and are usually controlled by computers and automated measurement equipment.
positive sequence the set of balanced normal (abc) sequence components used in symmetrical components. Balanced load currents, for example, are strictly positive sequence.
positive transition angle
the angular portion of the time-based output signal (in degrees) that has a positive slope. This quantity could be loosely interpreted as the "leading edge" angle.
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