TRANSDUCTOR RELAYS
TRANSDUCTOR RELAYS
INTRODUCTION
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Transductor relays works
on the principle of variation in the inductance.
l
Transductor are magnetic
relays or magnetic amplifier.
l
The transductor
controlling a simple slave relay, makes its possible to reduce a complex
electromechanical device which operates in accordance with the interaction of
fluxes and current in a fully predictable way.
l
Since their operation is
mainly dependent on static components whose characteristics are easily
predetermined and checked. As a result than electromechanical relays and their
maintance is practically negligible.
lA transductor comprises essentially a magnetic core on which there are
two groups of windings, they are Operating Winding and Control Winding.
lThe windings of the different groups are not magnetically linked.
lThe operating windings are energized with A.C and control windings are
energized with D.C
lA Transductor operates so as to present a variable impedance to currents
flowing in the operating winding the magnitude of this impedance being varied
by the current in the control winding.
lIf used as an amplitude comparator it is limited in its senstivity by
the sensitivity of the slave relay in its output circuit. If used as a phase
comparator to obtain greater sensitivity it is dependent upon an external A.C.
supply which is sometimes difficult to arrange.
lThe restraining current thus obtained is rectified and partially
smoothed by the short circuit effect of the rectifier on control winding and
also due to the short circuit coupling winding.
lThe effect of this is to drive both the limbs on which the operating
winding is would into saturation.
lThe operating winding is would in such a way that the operating
ampere-turns oppose the restraining ampere-turns in one limb & strengthen
with new force them in the other.
lThe operating current would drive out of saturation the limb in which
operating current is against the restraining ampere-turns.
lWhen the peak value of the operating current exceed the magnitude of
restraining current when this happens a voltage is induced in the output
winding and the relay is energized.
lThe same operation is repeated on the others limb during the next half.
l
The slave relay current
is very low until the above mentioned condition exists. Then it suddenly
increases and becomes very large for a small value of operating current.
l
For this reason a heavy
duty of telephone type of relay is used with large setting.
l
Due to smoothing and
rectifying a signal, a delay is introduced because of the time constant of the
smoothing circuit and hence the operating speed is low.
APPLICATIONS
lIt is used in railway locomotive
lOn magnetic amplifier in Aircraft applications
ADVANTAGES
l It is used as low level currents and voltage measurements.
l Current limiter for electrical transmission/ distribution.
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