Page 95 - CITS - Electronic Mechanic - TT - 2024

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.

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CITS : E & H - Electronics Mechanic - Lesson 48 - 55