Over voltage and Under Voltage Protection System

Under and Over voltage Protection Circuits

Unexpected Changes in the power supply may become the cause many problems in the homes, offices and industries.  Voltage up down in the electric power have a very dangerous effect on connected load.  Fluctuations of over voltage and under voltage protection system are produced to control the bad effects. Generally these systems are used in water pumps, agriculture motors and etc. We are going to discuss the different control structures like timers and compactors of the under voltage and over voltage protection system in this article.

What is an Over Voltage and Under Voltage?

When the voltages in any circuit exceeds from its upper limit is called as over voltage and when the voltages decreases from its lower limit is called under voltage. Depending on the duration the over voltage duration are like a transient, voltage spike and power surge. The given below graph shows the variations between the time and voltage in both over voltage and under voltage variations.


3.7V battery Charge Indicator


Over Voltage and Under Voltage Circuit Using Comparator

This circuit is used to trip the mechanism to protect  from the damage. Generally, in homes and industries, we observe that there is a frequently changes in AC power. Due to these changes of the AC power, the electronic circuits may damage easily. To avoid this problem we implement the tripping mechanism of over voltage and under voltage protection.

Components Needed

  • 12 volts transformer
  • IN 4007 (D1,D2)
  • 1k (R1,R2)
  • 5k pot (P1,P2)
  • BC 547 Transistors (T1,T2)
  • 12V relay (RL1)

Under and Over voltage Protection Circuits

How the Circuit Works

When the 220V or 120V mains supply is within the set limits, T2 (BC547 Transistor) will be conducting, rendering T1 (Transistor) in a non-conducting state.

When voltage is lower than the set limit, T2 cannot conduct, when results relay remain off.
This adjustment is done by setting up P2.

During an over voltage condition, T1 will get into a conducting state, de-energizing the relay. This setting is done by adjusting P1.

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