Automatic transfer switch for generator

Automatic transfer switch for generator, in this project you will learn about mostly used circuit of automatic transfer switch for small power generators. There are many automatic transfer switches are available in market. Some of them are expensive and some are cheap. The reason behind their price difference is type of technology used. There are two kind of Automatic transfer switches are available in market. Analog electronics based automatic transfer switch and digital electronics based automatic transfer switches. Analog electronics based transfer switches use analog electronics in their circuit like operational amplifier , comparators, transistors, diodes and mechanical relays etc. But there is no digital display in analog electronics based transfer switches. Digital automatic transfer switches are most commonly used now a days. Because it use liquid crystal digital display to show values of current and voltage to user. It also shows the status of AC main power and generator to show which power source is currently being feed to load. You can use as many functionalities as you want. Some examples are given below :

  • Over voltage and over current protection
  • Battery status or amount of battery charging available
  • protection alarm and many others.

In this project, I will discuss digital automatic transfer switch and give you brief idea about its circuit diagram and programming. I will discuss following things?

  • what is automatic transfer switch for generator?
  • main components used in automatic transfer switch.
  • circuit diagram of automatic transfer switch.
  • how to write code for automatic transfer switch?

As it name suggest, automatic transfer switch is used to transfer from one state to another. In electrical terms , it is used to transfer load from one power source to another power source. Although it have many applications, but in this project, we are using automatic transfer switch to transfer load between AC main power and generator in case of failure of either power source. Automatic transfer switches for generator is used to turn on generator automatically in case of non availability of main power source. it is also used to transfer load to generator after generator transient period. Block diagram of automatic transfer switch is given below :

block diagram of automatic transfer switch of generator
block diagram of automatic transfer switch of generator

Above block diagram is self explanatory, but if you still do not feel comfortable let me know with your comments.

main components used in Automatic transfer switches :

 Automatic transfer switch use following major components which are used to control the main function of ATS.

  • AC voltage measurement of main AC power supply from wapda and out put of generator A, it is used to sense either AC supply from wapda is availble or not. You should have a knowledge about alternating voltage measurement with the help of microcontroller. If you don’t know how to measure AC voltage using microcontroller, check following article :

  “AC voltage measurement using pic microcontroller

  • Microcontroller : it is used to measure AC voltages of AC main power from wapda and generator. It is used to take necessary actions against availability or non availability of either source. It is also used to display digital values of voltage and current on liquid crystal display.
  • Liiquid crystal display is used for digital display of current and voltage values. it is also used to show status of both sources.
  • Relays are used to transfer from one source to another based on actions performed by microcontroller subjected to availability of sources.

circuit diagram of automatic transfer switch of generator :

Circuit diagram of ATS using pic microcontroller is shown below. I have used pic microcontroller to measure voltage and to take necessary actions on relays.

circuit diagram of automatic tranfer switch
circuit diagram of automatic transfer switch for generator

I will post separate article on working of above circuit diagram and how to write code for this project. keep visiting our website to know more about this project. thanks 🙂

42 thoughts on “Automatic transfer switch for generator”

  1. Hello Bilal
    Thank for this good post.
    Could you please give a little explanation about the variable resistors connected to the PIC and about the role of the third relay because I think that two relays are sufficient to switch between the AC power and the generator, aren’t they?

  2. Project  description
    Please I need information and a circuit diagram for Automatic changeover switch with wireless generator control abilities or mechanism.
    The generator rating is going to be between 2.2kva up to 2.5kva, and must be an automatic embedded systems generator on its own not the manual gen set.. Single phase generator and the Mains will be single phase too.. Ie 220volts 50hz…..
    The system will be  designed to select between two available source of power Givin preference or priority to one out of the two sources of power.
    In this case, the selection is between public supply Mains and generator.
    The ATS should monitor the Mains supply and check for complete failure or power outage upon which it changes the load over to the generator supply, sends command to the generator wirelessly to start ie ON.. And when the public supply is restored the ATS detects this sends an OFF command to the generator wirelessly to shut down.

  3. Pleas I’m working on Automatic change-over switch with fuel level detector,using micro controller. could you please guide me on how the micro-controller works in the circuit.

  4. Dear Bilal Malik,
    I am working on “GSM based backup generator monitoring using pic16877A and SIM300” including
    * Fualt detection (Commercial power failure, breaker trip etc.
    *Generator status (Auto, manual, running…
    *Fuel level, running hours…


  5. I need ATS circuitdiagram ATS in proteus with complete cote working in proteus,
    may u send me for practice,
    I m 70 ears old and jobless so i sit in home and passing time without any business
    ABdul Majeed Tahir

  6. Hola señor bilal soy nuevo en el forum me gustaría si usted puede mandarme el diagrama completo del diagrama de circuito de interruptor de transferencia automática del generador o en que pagina lo puedo descargar porque en el sitio donde esta publicado no se ve bien el diagrama del circuito .. ATT Cesar serrano.

  7. ok! I am final year of last graduating electrical power engineering . I want to do the project on automatic transfer switch , please send the design and simulation of ATS.

  8. HI! BILAL
    thank you for posting this different projects. now I am graduating class of 2018 by electrical power engineering. so I want to do project on ” automatic transfer switch design and simulation ”. for this if you have any source or document on simulation part please send for me . our last presentation will held on February 29/2018 G.C so please please help me by complete simulation of the circuit of automatic transfer switch .
    I wait you as you will send within this week on my site [email protected]
    thank you

  9. Hi Bilal

    Could you please let me know if this system is sending a start and stop pulse to generator or it is just transfering the switch. Can we implement start and stop pulse with a required duration.

    I need your help, My email ID is [email protected]

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