Resolver Control Transmitter & Resolver Control Transformer

In this article, principle, construction and working of resolver control transmitter and resolver control transformer is given.
Synchro is often referred as cousin of resolver.
People often interchange term for resolver as motion feedback sensors, transducer sensors, encoders and rotary position sensors.
The application of resolver in the military, product packaging plants and stamping press lines.
There are two types of resolvers

Resolver Control Transmitter

It is a rotary transformer in which magnitude of stator energy varies sinusoidally as the shaft rotates.

There are two windings in the resolver in which one primary winding or reference winding and two secondary windings ( SIN winding and COS winding ).
The primary winding or reference winding is embedded in the rotor and supply given to it via rotary transformer.
There are two windings embedded in stator slots which are at 90 degree mechanically displaced.
An alternating supply is given to reference winding by rotary transformer, no need of brushes and slip rings.

When alternating supply ( V_r ) is given to reference winding, voltage induced in the stator SIN winding and stator COS winding.
The two windings are displaced at 90 degree so it is called as SIN winding and COS winding.
The magnitude of the induced voltage depends upon multiplication of reference voltage and SIN or COS angle of input shaft from electrical zero ( EZ ) point.

V_S = V_r Sin θ

V_C = V_r Cos θ

The rotor shaft position θ depends upon SIN winding and COS winding.

Tan θ = V_S / V_C

The ratio of two voltage represents absolute position of shaft.

Shaft position of rotor θ = Tan ^{– 1} ( V_C / V_S )

When rated alternating voltage is given to the rotor winding at rotor initial position ( zero degree ), zero voltage induced in the stator SIN winding ( SIN 0 degree = 0 ) and maximum voltage induced in the stator COS winding ( COS 0 degree = 1 ), this position is called as electrical zero ( EZ ) position.

It has two stator winding ( SIN winding and COS winding ) and one rotor winding.
The rotor output voltage is directly proportional to sine of angle difference between input angle of stator and mechanical position of shaft.
The rotor voltage is directly proportional to Sin ( Φ – θ )

Where θ = Reference position of shaft

Φ = Stator input angle