Page 261 - Electrical Engineering Dictionary

equilibriummanifold Seeslidingsurface. equivalenceinlogic fortwoBooleanvari-
ables x and y, defined as

equilibrium point for a continuous-time (x ≡ y) = (¯x ∧¯y) ∨ (x ∧ y)
system dx/dt = f(t, x), a constant solution
∗
∗
x such that f(t, x ) = 0. For a discrete-
equivalence theorem an electromagnetic
time system x(k + 1) = f (k, x(k)), a con-
theorem: If the tangential magnetic and elec-
∗
∗
∗
stant solution x such that x = f(k, x ).
tric fields are known everywhere on some
closed surface S, then these fields may be re-
equilibrium solution consider a dynamic
placed with equivalent electric and magnetic
system described by a first-order vector dif-
surface currents, respectively. These equiv-
ferential equation of the form
alent currents will produce the same field
structure exterior to S as the original fields
˙ x(t) = f (x(t), t, u(t))
and the null field internal to S.
If there exists a vector x e such that
equivalent circuit a combination of elec-
tric circuit elements chosen to represent the
f(x e ,t, 0) = 0 ∀t
performance of a machine or device by es-
tablishing the same relationships for voltage,
then whenever x(t) = x e , the system is said
current, and power.
to be in equilibrium and x e is called an equi-
librium state.
equivalent control an algorithm used
to determine a system’s dynamics when re-
equilibriumstate Seeequilibriumsolution.
stricted to a sliding surface. The method
entails combining the solution to an alge-
braic equation involving the time derivative
equipment hazard a possible source of
of the function describing the sliding surface
peril, danger, risk, or difficulty.
and the dynamical system’s model. See also
variable structure system and sliding mode
equiripple filter a filter designed using an
control.
iterative algorithm, for example, Remez ex-
change algorithm, to minimize the maximal
equivalent current a theoretical current
deviation from the desired magnitude fre-
used to obtain the scattered field from a sur-
quency response in both passband and stop-
face or discontinuity. The equivalent current
band for a given filter length. It has equal
is formulated to represent the actual physi-
amplitude ripples within the passband and
cal currents so as to result in an equivalent
stopband. See also Chebyshev filter.
scattered field.
equivalence in continuous-valued logic equivalent impedance the impedance of
similar to equivalence in conventional logic the windings of an electromagnetic machine
equivalence in continuous-valued logic be- reflected to one side (component) of the ma-
tween two variables x and y, which are con- chine. For example, in a transformer, the
tinuous in the open interval (0, 1), can be de- equivalent impedance consists of the com-
fined as bined leakage reactances and resistances of
the primary and secondary.
e(x, y) =
max{min(x, y), min((1 − x), (1 − y))} . equivalent noise current (ENI) a noise
current source that is effectively in paral-
See equivalence in logic. lel with either the noninverting input termi-
c
2000 by CRC Press LLC