Basic Types of Voltage Stabilizers

Voltage fluctuations cause temporary or permanent failure of the load. These voltage fluctuations also reduce the life span of the home appliances due to the unregulated low or higher voltage than the intended voltage required for the load. These voltage fluctuations occur due to sudden load changes or due to faults in the power system. So, it is required to supply stable voltage to the load, considering home appliances’ importance and the need for their protection. Voltage stabilizers are used for maintaining a stable voltage supply to the load such that the home appliances can be protected from over and under voltages.

What is Stabilizer?

A Stabilizer is a thing or device used to maintain something or a quantity steady or stable. There are different types of stabilizers based on the quantity they are used for maintaining stability. For example, a stabilizer used for maintaining the voltage quantity stable in a power system is called as voltage stabilizer.

What is Stabilizer?
What is Stabilizer?

Voltage Stabilizer

Voltage stabilizer is designed for maintaining the stable voltage level to provide a constant supply in spite of any fluctuations or changes in supply in order to protect the home appliances. Generally voltage regulators are used to maintain constant voltage and these voltage regulators which are used to provide constant voltage to the home appliances are called as Voltage Stabilizers.

Voltage Stabilizer
Voltage Stabilizer

There are different types of voltage regulators such as electronic voltage regulators, electromechanical voltage regulators, automatic voltage regulators and active regulators. Similarly, there are different types of voltage stabilizers such as servo voltage stabilizers, automatic voltage stabilizers, AC voltage stabilizers and DC voltage stabilizers.

Voltage Stabilizer Working

The working of the voltage stabilizer can be studied by considering the different types of voltage stabilizers, such as:

AC Voltage Stabilizers

These AC voltage stabilizers are classified into different types such as Coil rotation AC voltage regulators, Electromechanical regulators and Constant-voltage transformer.

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.

Coil Rotation AC Voltage Regulators
Coil Rotation AC Voltage Regulators

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.

Electromechanical Regulators
Electromechanical Regulators

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.

Constant Voltage Transformer
Constant Voltage Transformer

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.

DC Voltage Stabilizers

Series or Shunt regulators are frequently used for regulating the voltage of the DC power supplies. A reference voltage is applied using a shunt regulator like Zener diode or Voltage regulator tube. These voltage stabilizing devices start conduction at a specified voltage and they will conduct maximum current to hold the specified terminal voltage. Excess current is diverted to ground often using a low-value resistor for dissipating the energy. The figure shows the DC-adjustable-voltage stabilizer using IC LM317.

DC Voltage Stabilizers
DC Voltage Stabilizers

The shunt regulator output is used only for providing the standard reference voltage to the electronic device called as voltage stabilizer, which is capable of delivering much larger currents based on the demand.

Automatic Voltage Stabilizers

These voltage stabilizers are used on generator sets, emergency power supply, oil rigs, and so on. It is an electronic power device used for providing variable voltage and, this can be done without changing the power factor or phase shift. Large sized voltage stabilizers are fixed permanently on the distributed lines and small voltage stabilizers are used for protection of the home appliances from the voltage fluctuations. If the voltage of the power supply is less than the required range, then a step up transformer is used for stepping up the voltage levels and similarly if the voltage is greater than the required range, then it is stepped-down using a step-down transformer.

Automatic Voltage Stabilizers
Automatic Voltage Stabilizers

Practical example of automatic voltage stabilizer can be observed in power supply circuits used to provide supplies to the electronic and electronic circuits. Frequently 7805 regulator is used for providing supply to the microcontroller based project kits as the microcontrollers operate at 5v. In this 7805 voltage stabilizer, the first two digits represent the positive series and the last two digits represents the output voltage value of the voltage regulator.

7805 Regulator
7805 Regulator

Advancement in technology developed many new trend voltage stabilizers which automatically adjust the voltage levels in the required range. In case of a failure to achieve this required range of voltage, then the power supply will be automatically disconnected from the load to protect the home appliances from undesired voltage fluctuations. For more technical information regarding the voltage stabilizers, you can feel free to contact us by posting your comments in the comment section below.

Photo Credits:

  • Coil Rotation AC Voltage Regulators by writework
  • Electromechanical Regulators by wikimedia
  • Automatic Voltage Stabilizers by click


  1. What’s the appropriate voltage stabilizer I can use for my 32 inch LED digital flat screen television.

  2. Odewale. O. Olanrewaju says:

    Pls, how will I get a stabilizer to power a 6- bedroom apartment? And where?

  3. Raza ellahi kochak says:

    Hi i am making my college project on servo motor control voltage stabilizer using toroidal transformer. I would be really thankful of you could help me with any research paper or technical specifications thankyou

  4. Hi,
    I want to buy voltage stabilizer for CNC machines. Should i buy an a.c voltage stabilizer or a d.c. voltage stabilizer ? A.C. gives 60V correction and D.C. gives 105V correction. I have a voltage problem in my area.

  5. Hi, If we consider the stabilizer having 1.3 amp capacity and 90 – 290 v operating range , time delay of 8 seconds.
    The manufacturer claims that it is suitable for ONLY 32 inch LED television. Shouldn’t it support 43 inch as well?

  6. I have a duro max model DMP DX 1404 stabilizer bought frm Whirlpool company for my Whirlpool refrigerator.Since a month now the power to the refrigerator is cut off as soon as the indicator on the stabilizer shows ‘High’ (>260V). Is it not supposed to reduce the voltage and maintain a steady current to the refrigerator.
    I wish to know that since there is one more option of ‘overload ‘ on the stabilizer which trips the device and cuts off power then when input power is ‘high’ it should not cut off current to the refrigerator.
    This is happening everyday at night around 11 p.m. till 6 a.m.Pls help as My refrigerator remains powered off for abt 7 hrs daily at night.The power supply to the houses in our location shows a voltage of 258V during daytime.Is that permissible?Should this be brought to the notice of MSEDC ?Pls help
    Thnx b Rgds

    1. Tarun Agarwal says:

      Hi Manisha,
      Is this your requirement for commercial purpose?
      But we don’t deal the projects for commercial use.
      For more details please contact Mr.Tarun Agarwal on +91-9908208883

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