TRANSDUCTOR RELAYS

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TRANSDUCTOR RELAYS

INTRODUCTION

l 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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