Readers are advised to proceed with the construction of the presented circuits only after understanding the concepts from the core. Not adhering to this can lead to failures and frustrations.

Search This Blog

Loading...

Thursday, December 13, 2012

Single Transformer Inverter/Charger/Changeover Circuit

An inverter circuit design  may be quite incomplete if it's without an appropriate integrated battery charger circuit. Though you may find many inverters having an integral battery charger, the section will mostly employ a separate transformer for implementing it. The following article describes a unique design which utilizes the inverter transformer for power inverting as well as for charging the battery.


The circuit diagram below shows a design where a single power transformer is used for inverting purpose as well as for charging the battery when mains is present.

The good thing about the circuit is that the transformer doesn't employ separate winding for this, rather works with the same input winding and reverts DC to the battery with the help of a few DPDT relays.

The circuit can be understood with the following points:


The inverter section can be easiy recognized in the diagram, R1 to R6, including the T1 and T2 forms a general astable multivibrator circuit for producing the required 50 or 60 Hz pulses.

These pulses drive the mosfets alternately which in turn saturate the transformer by switching the battery voltage in it. The secondary of the transformer generates the corresponding magnitude of AC which is finally used for operating the connected appliances.

The above configuration suggests an normal or ordinary inverter operation.

By adding a couple of DPDT relays in the above discussed operation, we can force the circuit to charge the battery in the prsence of an AC mains source.

The coils of the two relays are powered through a capacitive low current compact power supply, involving C6, C5, D1----D5.

The above circuit is connected to a mains AC source, this source is also connected to RL1 poles.

The second relay RL2 is wired up with input winding of the transformer.

In the absence of mains AC, the position of the relay contacts are in the N/C as shown in the figure.

In this position the mosfets get linked with the transformer input winding, and thea battery with the circuit so that the inverter starts oscillating and the output appliances gets the AC power from the battery.

In the presence of mains AC the relay coils instantly get the required DC power and the contacts activate.

RL1 activates and connects the mains input to the transformer, the appliances also get connected with the mains AC in the process.

Also due to the action of RL2 the mosfets get disconnected from the transformer, while the the lower tap connects with D6. Since the center is already connected to battery positive, the inclusion of D6 provides a half wave rectified voltage to the battery, which is effectively filtered by C3 so that the battery is able to get the required sufficient charging voltage.

The above charging process continues until mains is present, so it should be monitored manually. When mains fails, the action reverts into inverting mode without interrupting the appliance operations and by using a single transformer for both the operations.

C4 makes sure that RL1 always activates a shade later than RL2 for safety reasons.


Parts List

R1, R2 = 27K,
R3, R4, R5, R6 = 470 Ohms,
C1,C2 = 0.47uF/100V metallized
T1, T2 = BC547,
T3, T4 = any 30V, 10amp mosfet, N-channel.
C3 = 47000uF/25V
C4 = 220uF/25v
C5 = 47uF/100v
C6 = 105/400V
R7 = 1M
D1---D5 = 1N4007
D6 = 1N5402
RL1, RL2 = DPDT, 400 OHMS, 12V, 7 AMPS/220V
Transformer = 12-0-12V, current as per requirement.

For only inverter design please refer to this ARTICLE

77 comments:

  1. Hi swagat,
    This is a good idea. But We need 14.3v DC to charge a 12v lead acid battery.If we planning to make an automatic trickle charger, then we need 18v DC. You are indicating that the inverter transformer is 9-0-9 8A. So how can we charge a 12v battery with a 9v transformer.?

    ReplyDelete
    Replies
    1. Hi Vinod that's correct, you may make the transformer 12-0-12V for enabling proper charging of the battery.

      Delete
  2. sir, Can i use the car battery for this circuit and what are modification for this circuit. how many watts output obtain in this circuit by using car battery and i want to run ceiling fan .. pls help for this..

    Thank you ..

    ReplyDelete
    Replies
    1. Yes you may use a car battery with this circuit.

      You will have to use a 10amp, 12-0-12V transformer, then you would get an output of about 120 watts. you can run a ceiling fan with it.

      Delete
  3. Helo mr swagatam...please can you help me design a circuit to charge 25 li-on cell battery(3.7v- 800mA each) at the same time.my power source is from 12v- 50AH battery. Also let me know how many amps of the 12v battery would be drawn with this setup per hour...thanks in advance

    ReplyDelete
    Replies
    1. Hello Haruna,

      I have noted down your request, I'll try to publish the required circuit soon in my blog, will inform you when it's posted.

      Delete
  4. Dear Swagatam sir,

    Very good morning to you! how are you ? I am Maung Pru, from Bangladesh.

    Thank your very much for your thousands of valuable circuits.

    I would like to have some info on this circuit, would you please kindly advice me that ..

    Q1. using an external DC charger would it be possible to charge the battery from inverter AC out ? while same time powering other lights and fan ?

    Q2. if so, what would be the battery life cycle ? the battery plates may damage ?


    Thank you and with best regards

    Maung Pru

    ReplyDelete
    Replies
    1. Hi Maung,

      many people have asked this question to me, and the answer is always a "NO!"

      It's due to two reasons:

      First of all charging will require much more time than the back up time.

      If you use high current charging adapter, then all the power will go to the battery, and none to the appliances.

      Second, due to inefficiency the output from the inverter will be always 10 to 20% lower than the total input supply power.

      Delete
  5. Dear sir,

    Thank you very much for your response with valuable comments.

    for your kind info, we live in hilly area Bangladesh, some time the power go off for 3-4 days. we need the power, which will be constant and non stop supply. but don't have it.

    sir, can it be able to run for at least 3 days ? please help us.


    3000 Watt Generator Powers Itself, Grinder & Drill Press.
    http://www.youtube.com/watch?v=Fv53K9MnDuM


    Thank you and with best regards

    Maung

    ReplyDelete
    Replies
    1. Dear Maung

      Can you explain me what's the concept about? I couldn't understand anything from the video....???

      Delete
  6. Love your work.What are the mosfets names and transistors?

    ReplyDelete
    Replies
    1. transistors are BC547

      mosfets are IRF540n

      Delete
  7. You are a genius. Can the charger charge 12v 200ah battery.

    ReplyDelete
    Replies
    1. thanks! for chaging a 200 ah battery, the transformer will need to be 25Amp rated.

      Delete
  8. Hie swagat. i can you help me with the complete part list of this diagram. Thanks

    ReplyDelete
    Replies
    1. I have updated it in the article, please check it out.

      Delete
  9. Thanks for your time and dedication .I hav a 600w 12-0-12 transformer if i use it on this diagram would it work and how many watts do i get at the output? Q2- if i use 3205 instead of irf540n wil it work?

    ReplyDelete
    Replies
    1. Yes it should work according to me,...with 600 watts naturally you would get something around 600 watts provided the battery is also rated appropriately.

      Delete
    2. Hello, Engr. Swagatama,
      You have done a great job to save people, thank you.
      I read mechanical engr but have interest in electrical work.
      I want to buid a 50w inverter from the past analysis u have been given before i can build a bigger one for my family use.
      I have been looking for person that will answer small small questions the way u do but i have not seen. Thanks for your time and effort.
      From Tony.

      Delete
  10. hello swagatam
    i want to bild the above circut but RL1 and RL2 beside C4 and D5 connected to mains

    ReplyDelete
    Replies
    1. no, those are connected to the bridge rectifier, the broken lines indicate that they are not connected.

      Delete
    2. Hi swagatham

      In the circuit beside c4 they are coils?
      If yes what is the rating

      Delete
    3. those are the coils of the two relays whose contacts are used for switching the transformer winding.....

      Delete
    4. what is the rating of the coil

      Delete
    5. the relay coils are rated at 400 ohms.

      Delete
  11. Hi swagatham
    What is the wattage of the circuit given
    And what are the modifications needed for 600w output

    ReplyDelete
    Replies
    1. for 600 watt, use a 600 watt transformer, IRF3205 mosftes and a 200 ah battery

      Delete
  12. Thanks for your time admin. Were can i connect power on led and inverting led?

    ReplyDelete
    Replies
    1. one led across N/C to ground, another across N/O to ground of RL2 contacts (upper one), each led should have its own 2k2 resistor in series.

      Delete
  13. Thanks Mr Swagatam, suppose I want to use 12V-0-12V transformer for a 24V-0-24V transformer, how will I do it?. Secondly, how can someone build an inverter of Wattage rating of his choice through calculations of components to be used and the numbers

    ReplyDelete
    Replies
    1. Acquiring 24V from 12V is difficult and is not recommended, because the transformer can become hot.

      Wattage rating can be controlled by controlling the battery current through some circuit stage.

      Delete
  14. DEar sir,
    Can i use a 10 A relay instead of the 7 A one used here

    What precaution should be taken in order to safeguard the entire circuit before applying the ac mains to transformer's primary ?

    And one more doubt sir
    What does the connection (which seems like inductor coil )in the upper circuit means ? I realize that these are the connections across two relay pins and the upper circuit is the power feeding circuit for the relays. But i can't understand the 2 pins that i specified here. Please help me sir. I am not at all familiar with relays. Hoping your reply very soon sir......

    ReplyDelete
    Replies
    1. Dear Arun,

      Use a 100 watt bulb in series with one of the input mains wires for safety.

      The inductors are the relay coils, a relay cannot be activated unless its coils are energized therefore these coils are supplied through the capacitive power supply shown at the upper section of the diagram.

      Delete
    2. ....you may refer to this post for knowing more about relays:

      http://homemadecircuitsandschematics.blogspot.in/2012/01/how-to-understand-and-use-relay-in.html

      Delete
  15. Sorry for disturbing you again sir. But what to do.... I have to be completely free of doubts before going for the design..... This time i am also coming with another doubt which may feel silly to you, please dn' t neglect it since i am not having deep knowledge in Electronics, but i like it.

    I have a 300 W 12 V transformer having 4 thick windings at primary and 5 at secondary. I know it is a multi-tap one. But don't know how to wire them to suit for the single transformer inverter design.. Please help me......



    How can i link the images with the comments in this blog ?

    ReplyDelete
    Replies
    1. You can connect the 220V wires to mains and measure the tap voltages with a multimeter, in this way you would be able to figure out the tap values.

      Delete
    2. you can upload the images on any free image hosting site and provide me the link.

      Delete
  16. Sir that was not enough..... I need a better suggestion.......
    My transformer is a locally made one. No markings ( even no separate colors for wires ) are there. The only thing that i could see that some set of the terminal wires are thicker than other set. From basic calculations of transformer design, i think the wires to bear large current are of secondary ( 300 W/ 12V ) and they have to be thick enough than the primary. Am i right ? If not please correct me.....
    I am in a little bit confusion that how to connect the neutral and earth lines of ac mains into the transformer if it has 5 primary terminals as i calculated..... Please help me sir... Can you please suggest the exact connection schematics.....
    Since it is an ac transformer, i willn't be able to measure the tap voltages exactly without a brige type rectifiers. Taking each tap voltage by changing the polarities supplied to the rectifier will be very time consuming..
    I couldn't upload the images of the transformer.... SO PLZ HELP ME

    ReplyDelete
    Replies
    1. you won't need a bridge rectifier at each tap for checking, you can do it with your meter on AC 220V range.

      you can also check the taps by measuring their resistances...the one which gives the highest resistance can be assumed to be the mains input winding, connect a 100 watt bulb in series which testing with mains for avoiding possible hazards.

      Delete
  17. Very nice circuit sir.
    Can i use a 300 W transformer in this circuit ? How much high will be the currents in both terminals ? Can i use the formula P= IV for its calculation. If i am doing so i will get maximum current
    In primary : 1.304 A and
    In secondary : 25 A........ Is that will happen ?

    If so, that diode (IN5402) used in Charging section sufficient to overcome this high amperage ?
    What about the diodes at the primary if i am using the inverter to be run on a 300 W load. Reply me soon plz....... Sorry for the bad english...

    ReplyDelete
    Replies
    1. Thanks Ramsree,

      You can use P = IV, 25amps is right but that might be too high for the battery, because as per rules the ideal charging current should be 1/10th of batery AH, so we may have to upgrade the circuit with an additional current limiter circuit and also some modification in the relay wiring.....

      Delete
  18. What modification you mean sir ? How can i modify this circuit to charge a 60 Ah battery bank effectively ? Can i use your one of previous post on ' 3 stage smart battery charger for 12 V ' with this.circuit ? What modifications to be done sir ?

    ReplyDelete
    Replies
    1. a simpler approach would be to add a calculated current limiting resistor in series with D6

      Delete
  19. Dear sir,
    Can you please give a model current limiting circuit to fullfill my need ? Can i have it to be used prior to the rectification section ? Thereby i can avoid using high ampere diodes there. that is why

    ReplyDelete
  20. Another doubt too sir,
    If i am using battery rated below 100 Ah along with the current limiting circuit , will it be possible for the inverter to run maximum load that i am expecting with ?

    ReplyDelete
    Replies
    1. As mentioned in the previous comment, the series resistor with D6 will not interfere with inverter power outputs, it will work with the specified full capacity

      Delete
  21. Thank you so much for this post. I will like to give you feed back after I complete the work and I will also prefer to know about circuit diagram.

    Kindly, let me ask this question.
    1. Is it possible to use this circuit with 24volts battery without any damage to the cell of the circuit?

    ReplyDelete
    Replies
    1. Yes, 24V can be used, provided the transformer and the relays are also rated at 24V.

      Delete
  22. Hi Swag,
    is it possible to use transformer with 6v - 0 - 6v and if yes what will be the output of it?

    Thanks.

    ReplyDelete
    Replies
    1. Hi Adeleke,

      it would work with a 6V battery...output would be equal to the output rating of the transformer, if it's 220v then it would generate 220V

      Delete
  23. Hai sir,
    Can i ask you something......
    What modification to be done to the present circuit if i am using high current transformer ??
    A series current limiting resistor alone will not do this purpose i think. What extra things to be added to the oscillation section to prevent ir from accidental damage due to high current flow. Also i want to know the necessary changes to be made on relay wiring also. Please try to REPLY MY ALL QUESTIONS SIR

    ReplyDelete
    Replies
    1. Hi Venkitesh,

      I'll try to find some appropriate solution and update it soon.

      Delete
  24. Hai sir it is again prithviraj speaking.....
    A serious doubt is now disturbing me....
    As per your suggestion, the inverter o/p after successful testing can be connected directly to the ac wall outlet. But in this inverter schematics, the relay coils are actuated by the ac mains. So if i am gonna follow my strategy, will the relay actuate on getting supply during inverter operation and continously turn ON and OFF ?????

    ReplyDelete
    Replies
    1. Hi Prithviraj,

      You are right, the above inverer cannot be inserted in the wall socket, because the relays would start vibrating ON/OFF due to the particular configuration employed in the circuit.

      Delete
  25. Thank you Sir for replying me fast. Now i want to know whether any modification can be done to the present structure to suit my need or can you suggest any other design for me. I know i am disturbing you a lot. But what to do, i willn't get a better sleep if the problem is kept unsolved....
    I am not at all interested in connecting appliances directly to inverter terminal out, because it will cause discomfort in turning a particular device on at a room

    ReplyDelete
    Replies
    1. I am sorry Prithviraj, there's no possible way out with the above circuit We can consider a manual option using DPDT switch for the changeovers.

      Delete
  26. Sir i think it is possible to solve the issue by any of these,,,,,,,,
    What about using a descriminator circuit to distinguish the sinewave from the square wave( which is produced by the inverter ) and actuating the relay only on sine wave, i.e, during mains is present.
    Another way i think, is to slightly make a change to the existing frequency of square wave ( which is 50 Hz ) and thereby identifying the power on condition by counting frequency of the incoming signal to the relay coil fed.

    But i don't know how this will take effect or will be effective and also don't know how to arrange these modifications. ..... So can you please help me

    ReplyDelete
    Replies
    1. I don't think that would help, in that case when the mains comes back it will first clash with the inverter AC and cause undesirable things to happen, a fire, a blown fuse etc. because once the the inverter AC gets into the wall socket it's bound to mix with the mains AC unless a DPDT is employed for isolating the respective ACs manually

      Delete
  27. Hellow sir, how did you calculate the value of resistors and capacitors incorporating the AMV stage of two.coupled transistors. I have to place available and suitable components there

    ReplyDelete
    Replies
    1. Hello Rishikesh,

      you can use the following formula
      f = 1/1.4CR. where C = C1 = C2, and R = R1 = R2

      R will be be in OHMs and C in FARADS

      Delete
  28. If the relay fails, won't it be dangerous to the inverter?

    ReplyDelete
    Replies
    1. yes it could be dangerous, we can include a safety fuse for that in the circuit

      Delete
  29. hello Swagatam,
    I interested in this circuit diagram but being novice, I'm finding difficult to understand the connect basically the operation of dpdt relay.
    how many relays are required in this circuit diagram and how do I connect it pls
    Thanks

    ReplyDelete
    Replies
    1. Hello Agbadu,

      If you are new in the field please do not try this circuit, it's strictly for the experts.

      2nos DPDT relays are used in this circuit.

      Delete
    2. but pls sir can you explain the charging section relay connection for me
      also can this circuit be converted to 2.5kva, if yes how?
      Thanks

      Delete
    3. I have already explained it in the article, if you have a specific doubt you can ask it.

      if the above basic model is confirmed then it can be modified for 2kva also.

      Delete
  30. Sir, tanks for the post
    Pls I don't get how to connect RL2 to the two mosfet since one Relay is specified for the two I can only connection one successfully. Pls help explain

    ReplyDelete
    Replies
    1. RL2 could be a DPDT type relay having two sets of contacts but a single coil controlling both the contacts simultaneously

      Delete
  31. Thanks, try to DPDT type Relay

    ReplyDelete
  32. Hi sir, I'm unable to lay me hand on DPDT type relay, can I use 4 SPDT relay instead of DPDT relay, pls quick reply will be appreciated, thanks

    ReplyDelete
  33. Hi Swagatam, thanks for the he'll so far. Pls which capacitor can I use instead of C1,C2,C3 and C6 am unable to get those capacitors here. Thanks

    ReplyDelete
    Replies
    1. Hi Kolley,

      the capacitor values cannot be changed, so you'll have to use as suggested.

      the ones which are polarized need to be electrolytic while the others metallized polyester type.

      please note that this project is not for the newbies and requires expert knowledge in the field...the circuit has the potentials of causing fire hazard and explosion if not done correctly.

      Delete

Readers are requested not to include external links while commenting. For consulting a diagram, upload it on Google Drive and provide the link here.