Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

compound-connected DC machine
a direct current machine with two field windings in which one field winding is connected
in series and one field winding is connected in parallel (shunt) with the armature winding. The shunt winding may be connected ahead of the series winding (long-shunt connection), or behind the series winding (short-shunt connection).
compound-rectifier exciter
a source of field current of a synchronous machine derived from the phase voltages and currents of the machine. The phase voltages and currents of the machine are fed through transformers, then rectified in order to provide DC quantities to the field winding. The components of the exciter are the transformers (voltage and current), rectifiers (including possible gate-circuitry), and power reactors; exclusive of all input control elements.
computer relay
a protective relay that digitizes the current and/or voltage signals and uses a microprocessor to condition the digitized signal and implement the operating logic.
See digital relay
computer-aided design (CAD)
field of electrical engineering concerned with producing new algorithms/programs which aid the designer in the complex tasks associated with designing and building an integrated circuit. There are many subfields of electrical CAD: simulation, synthesis, physical design, testing, packaging, and semiconductor process support.
cone of protection
a method used to determine the extent of protection to surrounding structures afforded by a tall, grounded structure like a steel tower. Proposed prior to the "rolling ball" model, this method suggests that any structure which can fit within a right circular cone whose vertex is at the top of the tower will be protected from lightning strikes by that tower. The angle of the cone's vertex is a matter of some controversy.

See rolling ball
constant-horse power drive
a variable speed drive that is operating in a speed region where it is capable of delivering rated power. For DC machines, this region is above base speed and is achieved by field weakening. For AC induction motors, this region is above rated speed and is achieved by increasing the frequency of the applied voltage.
copper loss
electric loss due to the resistance in conductors, windings, brush contacts or joints, in electric machinery or circuits. Also referred to as I2R, the losses are manifested as heat.
core-type transformer
a transformer in which the magnetic circuit upon which the windings are wound takes the form of a single ring. When the coils are placed on the core, they encircle the core.
See core
Ampere, Andre Marie (1775-1836)
Born: Lyon, France
Ampere is best known for his pioneering work in the field of Electrodynamics. During his emotionally troubled life, he held several professorships: at Bourg, Lyon, and at the Ecole Polytechnic in Paris. While Ampere worked in several sciences, the work of the Danish physicist Hans Christian Oerstad on the electric deflection of a compass needle, as demonstrated to him by Dominique Arago, caused Ampere's great interest in electromagnetism.
His seminal work, Notes on the Theory of Electrodynamic Phenomena Deduced Solely from Experiment, established the mathematical formulations for electromagnetics including what is now known as Ampere's Law. It can be said that Ampere founded the field of electromagnetics. He is honored for this by the naming of the unit of electric current as the ampere.
counterpoise
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.
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.
damper winding
an uninsulated winding, embedded in the pole shoes of a synchronous machine, that includes several copper bars short-circuited by conducting rings at the ends, used to reduce speed fluctuation in the machine by developing an induction-type torque that opposes any change in speed.
damping
a characteristic built into electrical circuits and mechanical systems that prevents rapid or excessive corrections that may lead to instability or oscillatory conditions.

damping coefficient
electrical torque component in phase with the rotor speed.
DC chopper
a DC to DC converter that reduces the voltage level by delivering pulses of constant voltage to the load. The average output is equal to the input times the duty cycle of the switching element.
DC input power
the total DC or bias power dissipated in a circuit, which is usually dependent on signal amplitudes, expressed in watts. This may include input bias, bias filtering, regulators, control circuits, switching power supplies and any other circuitry required by the actual circuit. These considerations should be explicitly specified, as they will affect how efficiency calculations are performed.
DC link capacitor
a device used on the output of a rectifier to create an approximately constant DC voltage for the input to the inverter of a variable speed AC drive.

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