Page 180 - Electrical Engineering Dictionary

angular frequency of the stationary flux, and counterpoise ground buried conductor
the magnitude of the rotating fluxes is half routed under transmission lines designed to
the magnitude of the stationary flux. Mathe- achieve low earth electrode resistance.
matically, this is described by the following
equation: coupled inductor two inductors within a
switching converter, which have similar volt-
B cos θ sin ωt = 0.5B sin ωt − θ age waveforms, are wound on the same mag-
+ 0.5B sin ωt + θ netic core to steer the ripple from one wind-
´
ing to another. A typical example is a Cuk
where the left-hand term represents the time- converterwithanisolationtransformerwhere
varying flux magnitude along the spatial di- the input and output inductors are coupled
rection θ, and the right-hand terms represent with the transformer to provide zero ripple
´
forward and backward rotating fields of con- at the input and the output. See also Cuk
stant magnitude rotating about θ. The fol- converter.
lowing diagram illustrates this relationship.
Resolution of the stationary flux into two ro- coupled line filter a type of microstrip
tating fluxes allows induction machine per- or stripline filter that is composed of parallel
formance to be analyzed using standard ro- transmission lines. Bandwidth is controlled
tating field theories. The total machine per- by adjusting the transmission line spacing.
formance is determined from the net result Wider bandwidths are obtained by tighter
of both rotating fluxes. Also called double coupling. A two-port circuit is formed by
revolving-field theory. terminating two of the four ports in either
open or short circuits, which leaves ten pos-
sible 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 prox-
imity can interact with each other to form
coupled lines. Usually three conductors are
needed. Examples of coupled lines are cou-
pled microstrip lines and coupled striplines.

coupled Riccati equations a set of dif-
ferential or algebraic matrix equations of
the Riccati type arising in the jump linear
Counter-rotating field concept. quadratic problem which should be solved
simultaneously. The set of coupled differen-
tial Riccati equations has a form
counter-torque torque developed in op- 0
˙
position to the rotation of a machine. It is K(i, t) + A(i) K(i, t) + K(i, t)A(i)
s
produced as load current flows in the pres- X
q ij K(j, t) + Q(i)
ence of and perpendicular to magnetic flux in
a machine that is generating electric power. j=1
0
− K(i, t)B(i)R(i) −1 B(i) K(i, t) = 0
counterpoise a ground wire buried be-
neath an overhead line to lower footing for i ∈ S ={1, 2,...,s}, t ∈[0,T ]
impedance. and terminal condition K(i, T ) = 0 where

c
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