Page 95 - CITS - Electronic Mechanic - TT - 2024
P. 95

ELECTRONICS MECHANIC - CITS




           1  Coil Rotation AC Voltage Regulators
           It is an older type of voltage regulator which was used in 1920s. It works on the principle similar to the variocoupler.
           It consists of two field coils: one coil is fixed and the other can be rotated on an axis which is parallel with the fixed
           coil.















           A  constant voltage can be obtained by balancing  the
           magnetic forces acting on the movable coil which is achieved
           by  positioning  the  movable  coil  perpendicular  to  the  fixed
           coil. The voltage in the secondary coil can be increased or
           decreased by rotating the coil in one or the other direction
           from center position.
           A Servo control mechanism can be used to advance the
           movable coil position for  increasing or  decreasing the
           voltage; with this coil rotation, the AC voltage regulators can
           be used as automatic voltage stabilizers.
           2  Electromechanical Regulators

           Electromechanical  voltage regulators that  are used for
           regulating the voltage on AC power distribution lines, also called as voltage stabilizers or tap-changers. To select
           an appropriate tap from multiple taps of an autotransformer, these voltage stabilizers utilize the servomechanism
           operation.
           If the output voltage is not in the range of intended value, then the servomechanism is used for switching the
           tap. Thus, by changing the turns ratio of the transformer, the secondary voltage can be changed to obtain the
           acceptable values of the output voltage. The hunting, which can be defined as the failure of the controller to
           constantly adjust the voltage; it can be observed in the dead band wherein the controller do not operate.
           3  Constant Voltage Transformer
           It is a type of saturating  transformer which  is used  as a voltage  stabilizer;  it is also  called  as ferroresonant
           transformer or ferroresonant regulator. These voltage stabilizers use a tank circuit composed of a capacitor for
           generating nearly constant average output voltage with varying input current and a high-voltage resonant winding.
           By the magnetic saturation, the section around secondary is used for regulating the voltage.





















           A simple, rugged method is used for stabilizing  an AC power supply which can be provided  by saturating
           transformers. Due to lack of active components, ferroresonant approach is an attractive method that relies on
           square-loop saturation characteristics of the tank circuit for absorbing changes in the input voltage.


                                                           80

                                    CITS : E & H - Electronics Mechanic - Lesson 48 - 55
   90   91   92   93   94   95   96   97   98   99   100