The increase of voltage sensitive equipment has determined a continuous request for means able to guarantee the supply of a steady voltage independently from variations in the network. Loss of data, defective products, security failure, machinery faults and inaccurate information are only a few examples of possible problems due to unstable supply.
The voltage stabilizer has proved to be an efficient answer in order to prevent from potential damages due to I/p voltage fluctuation. Installing a voltage stabilizer is the solution to ensure continuity and quality of production.
Our aim in this project was to develop single phase servo controlled voltage stabilizer control card and power card using microcontroller to provide better control than analog control card and make it user friendly by providing LCD display and keypad to adjust various process parameters.
Servo Controlled Voltage Stabilizer is used to stabilize the voltage fluctuation. Stabilizer is the Automatic Voltage regulator. It regulates the O/p power. It produces the O/p 230 VAC ± 1% (Variable 5%) (1-Ø) or 415 VAC ± 1% (Variable 5%) (3-Ø).
Power Diagram of Servo Controlled Voltage Stabilizer:
In servo stabilizer auto transformer has two tapings of which one is fixed and other is variable. These two tapings are connected to primary of buck boost transformer. According to the O/p voltage of stabilizer control circuit provide signal for servo motor to rotate in clockwise or anticlockwise direction. Rotation of servo motor cause sliding of variable contact of auto transformer. Thus primary voltage of buck boost transformer varies. So the secondary voltage of buck boost transformer varies.
There can be Analog or Digital control circuits for measurement and control purposes.
Analog Control Circuits:
Analog model consists of comparator, TRIAC & its driver or Relay & its driver to operate servo motor and for protection circuits, Voltage sensor using Potential Transformer,Therefore too much accuracy is required during design & also it should be redesign for any particular application or at least some minor tweaks are required and that should be very accurate(Mostly in Comparator part). Analog volt meter or 7 segment were used to display voltages, so it only makes feasible to display only one voltage at time either I/p or O/p.
Digital Control Circuits:
Digital model consists of microcontroller , TRIAC & its driver, Relay & its driver operate servo motor and for protection circuits, Voltage sensor, LCD display, Keypad.
In digital model I/p and O/p voltages can be measured by using op-amp circuits as at controller side one has ability to take sample of I/p and O/p signal at very high speed that it can be very precise. Due to use of microcontrollers its very easy to generate correction signals and provide very precise over or low voltage and over current protection. Set points for control signals and operation of servo motor can be set using keypad. And there is LCD to display multiple voltage and current at same time.
The purpose of designing Microcontroller based servo controlled voltage stabilizer is:
To provide true overload, over voltage and under voltage protection and over temperature protection which is possible by simple if…else logic in microcontroller programming and relay, it is very complicated using analog circuit.
Use of Keypad to set various set points & thus making device more user friendly than analog model where setting of various set points is quite complicated.
Provision of LCD display; which makes device look wise better than analog meter or 7-segment display.
Designing voltage sensing circuit using op-amp in place of costly & bulky potential transformer to reduce cost and space requirement without sacrificing the quality of output voltage by Measuring of true RMS values of voltage and current.