Electrical Engineers and Master Electricians (EEAME) Portal

Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

a manually-operated switch used to connect load conductors when an automatic transfer switch is disconnected.

a curve, generally polar, representing the variation of luminous intensity of a lamp or luminaire in a plane through the light center.

reactive power Q

The region of allowable operation is determined by factors such as rotor thermal limit, stator thermal limit, rated power of prime mover (alternator operation), and stability torque limit.

capacitance

the measure of the electrical size of a capacitor, in units of farads. Thus a capacitor with a large capacitance stores more electrons (coulombs of charge) at a given voltage than one with a smaller capacitance.
In a multiconductor system separated by nonconductive mediums, capacitance (C) is the proportionality constant between the charge (q) on each conductor and the voltage (V ) between each conductor. The total equilibrium system charge is zero. Capacitance is dependent on conductor geometry, conductor spatial relationships, and the material properties surrounding the conductors.
Capacitors are constructed as two metal surfaces separated by a nonconducting electrolytic material. When a voltage is applied to the capacitor the electrical charge accumulates in the metals on either side of the nonconducting material, negative charge on one side and positive on the other. If this material is a fluid then the capacitor is electrolytic; otherwise, it is nonelectrolytic.

capacitive reactance

the opposition offered to the flow of an alternating or pulsating current by capacitance measured in ohms.

capacitor bank

(1) an assembly at one location of capacitors and all necessary accessories, such as switching equipment, protective equipment, and controls, required for a complete operating installation.
(2) a group of (typically 3) capacitors mounted on an electric power line for voltage boosting or power factor correction.

capacitor-start induction motor (CSIM)

a single-phase induction motor with a capacitor in series with its auxiliary winding, producing nearly a 90. phase difference between the main winding and the auxiliary winding currents at starting. This results in a high starting torque, so this motor is used for hard-to-start loads. The auxiliary winding and capacitor are removed from the circuit by a centrifugal switch as the machine approaches operating speed.

circuit protection

devices or control measures used to safeguard electrical circuits from unsafe operating regions, such as over-currents and over-voltages.

circular polarization

a polarization state of a radiated electromagnetic field in which the tip of the electric field vector traces a circle as a function of time for a fixed position. The sense of rotation of the electric field vector is either right-hand or left-hand (clockwise or counter-clockwise).

coefficient of thermal expansion (CTE) mismatch

the difference between the coefficients of thermal expansion of two components, i.e., the difference in linear thermal expansion per unit change in temperature. (This term is not to be confused with thermal expansion mismatch).

coil pitch

See coil span

coil span

the distance, measured either in number of coil slots or in spatial (mechanical) degrees, between opposite sides of a winding of an electric machine. A full-span (full-pitch) winding is one in which the winding span equals the span between adjacent magnetic poles. Windings with span less than the distance between adjacent magnetic poles are called short-pitch, fractional-pitch, or chorded windings.

See coil pitch

color preference index (CPI)

measure appraising a light source for appreciative viewing of colored objects or for promoting an optimistic viewpoint by flattery.

color temperature

the color a black object becomes when it is heated. The standard color "white" occurs when a tungsten filament is heated to a temperature of 6800 degrees Kelvin. The temperature of 6800 K corresponds to a standard white raster as defined by the NTSC. The color temperature for white is useful for comparing color matching and color decoding among different displays that use different color phosphors. The standard "white" is obtained by mixing the 30% red, 59% green, and 11% blue color signals. Differences in the color saturation for the different phosphors found in television CRTs will modify the required proportions of red, green, and blue to produce the standard "white."

combined cycle plant

a gas-turbine power plant in which the exhaust gases are used to heat water in a boiler to provide steam to run a turbogenerator.

commutating pole

See interpole

compensating winding

a winding found in DC machines that is placed in the faces of the main field poles, and connected in series with the armature winding, to produce an mmf equal and opposite to the mmf of the armature, thereby reducing the effect of armature reaction.

compensation

(1) operations employed in a control scheme to counteract dynamic lags or to modify the transformation between measured variables and controller output to produce prompt stable response.
(2) the alteration of the dynamic behavior of a process by the addition of system blocks. These are usually connected in cascade with the original process on either its input or its output variables, or both. See also compensator, pre-compensator and post-compensator.

compensator

a system block added to an existing system (or process) to produce a combined transfer function that improves its performance when connected in a closed loop configuration. See also compensation, pre-compensator and post-compensator.