# Transfer Function of Synchro Transmitter Construction and Working principle

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## Transfer Function Of Synchros:

### What is synchro transmitter?

A Synchro Transmitter Receiver Trainer is an electromagnetic transducer commonly used to convert an angular position of a shaft into an electric signal. It is usually called a synchro transmitter. Its construction is similar to that of a three phase alternator.

### Construction of Synchro Transmitter:

#### The constructional features, electrical circuit and a schematic symbol of synchro transmitter are shown in the below figure. The two major parts of the synchro transmitter are stator and rotor. The stator is identical to the stator of the three-phase alternator.

It is made of laminated silicon steel and slotted on the inner periphery to accommodate a balanced three-phase winding. The stator winding is the concentric type with the axis of three coils 120° apart. The stator winding is star connected ( Y-connection). This basic construction will help you derive the transfer function of Synchros

### Working principle of Synchro Transmitter:

#### Let, the instantaneous value of rotor excitation voltage, er = Er sin ωt

Let the rotor rotates in an anticlockwise direction. When the rotor rotates by an angle,θ EMFs are induced in stator coils. The frequency of induced emf is the same as that of rotor frequency. The magnitude of induced EMFs is proportional to the turns ratio and coupling coefficient. The turns ratio, Kt is a constant, but coupling coefficient, K is a function of rotor angular position.

Induced emf in stator coil = Kt Kc Er sin ωt
Let es2 be reference vector. With reference to the above figure, when θ = 0, the flux linkage of coil S2 is maximum and when θ = 90°, the flux linkage of coil S2 is zero. Hence the flux linkage of coil S2 is a function of cosθ (i.e., kc= Kt cosθ for coil S2). The flux linkage of coil s3 will be maximum after a rotation of 120° in the anticlockwise direction and that of S1 after a rotation of 240°.