Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

corona resistance
capacity of a material to bear the action of the corona effect. This capacity is particularly important for polymeric materials, which have to withstand the chemical degrading effect promoted by ozone generated by the corona effect.

See corona effect
corona ring
a toroidal metal ring connected to discontinuities on high-voltage conductors to reduce local field intensity and thus discourage the formation of corona discharge.
Coulomb blockade
the situation in which a particle has insufficient thermal energy to allow the necessary energy exchange during a tunneling process. Hence, the bias supply must supply energy to the electron to account for the stored energy change in tunneling, which requires V > e/2C, where C is the capacitance (eV << kBT ).
Coulomb force
electric force exerted on an electrically charged body, which is proportional to the amount of the charge and the electric field strength in which the charged body is placed.

Coulomb's Law
the force of repulsion/attraction between two like/unlike charges of electricity concentrated at two points in an isotropic medium is proportional to the product of their magnitudes and inversely proportional to the square of the distance between them and to the dielectric constant of the medium.
Coulomb, Charles (1763-1806)
Born: Angouleme, France
Coulomb is best known for his study of electric charge and magnetism resulting in Coulomb's Law, as well as his studies in friction. Coulomb also invented the torsion balance in 1777. He used this device in many experiments. Coulomb began his career in the military, but resigned when the French Revolution began. His experience as a military engineer involved him in a wide variety of different projects. It also gave him time to continue his own experimental work.
Coulomb's law states that the force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance between the two charges. Coulomb is honored by having his name used as the unit of electric charge, the coulomb.
a voltage developed in an electrical winding by Faraday's Law that opposes the source voltage, thus limiting the current in the winding.
counter-EMF starter
a type of DC-motor starter that reduces the resistance in the starting circuit as the voltage across the armature rises.
torque developed in opposition to the rotation of a machine. It is produced as load current flows in the presence of and perpendicular to magnetic flux in a machine that is generating electric power.

a ground wire buried beneath an overhead line to lower footing impedance.
counterpoise ground
buried conductor routed under transmission lines designed to achieve low earth electrode resistance.

coupled line filter
a type of microstrip or stripline filter that is composed of parallel transmission lines. Bandwidth is controlled by adjusting the transmission line spacing. Wider bandwidths are obtained by tighter coupling. A two-port circuit is formed by terminating two of the four ports in either open or short circuits, which leaves ten possible combinations. Different combinations are used to synthesize low-pass, bandpass, all pass, and all stop frequency responses.
coupled lines
the electromagnetic field of two unshielded transmission lines in proximity can interact with each other to form coupled lines. Usually three conductors are needed. Examples of coupled lines are coupled microstrip lines and coupled striplines.
crest factor
the ratio of the peak value of a signal to its RMS value.
critical clearing angle
(1) following a balanced three-phase fault at the stator terminals of a synchronous machine, the maximum value of the angular position of the rotor prior to the removal (clearing) of the fault such that the rotor will obtain synchronous speed without slipping poles following the removal (clearing) of the fault. The corresponding time for the rotor to achieve this angle is specified as the critical clearing time.
(2) the largest allowable angular deviation from synchronism that may be borne by a power system such that the system remains stable: the edge of instability.
a transverse, generally insulated member mounted horizontally on a utility pole. It carries insulators and allows wide spacing of overhead conductors.
crossarm brace
a brace, often insulated, which keeps a crossarm from rotating on its attachment bolts.

See current transformer

See coefficient of utilization
cumulatively compounded
a compound-wound DC machine in which the flux produced by the MMF of the shunt field winding and the flux produced by the MMF of the series field winding are in the same direction.