Skip to main content

3-Phase Signal Generator Circuit using Opamp

Many a times we find it crucial and handy to possess a true three phase signal for evaluating many different electronic configurations such three phase inverters, three phase motors, converters etc.

Since it's not so easy to incorporate single phase to three phase conversion quickly we find this particular implementation difficult to acquire and enforce. The proposed circuit enables the above discussed well calculated spaced and positioned sine waves outputs to be generated from a single master input source.

Simulation and Working


The circuit functioning of the three phase waveform generator circuit may be understood with the help of the following explanation:

An input sine sample waveform is fed across the point "input" and ground of the circuit.This input signal gets inverted and buffered by the unity gain op amp A1. This inverted and buffered signal acquired at the output of A1 now becomes the new master signal for the forthcoming processing.

The above buffered master signal gets once again inverted and buffered by the next unity gain op amp A2 creating an output with zero degree initial phase across the points "Phase1"

Simultaneously, the master signal from A1 output is phase shifted by 60 degrees via the RC network R1, C1, and fed to the input of A4.

A4 is set up as a non-inverting opamp with a gain of 2 in order to make up for the signal-loss in the RC configuration.

On account of the fact that the master signal is phase shifted 180 degrees from the input signal, and further shifted to an additional 60 degrees by the RC network, the ultimate output waveform gets shifted by 240 degrees, and constitutes the "Phase3" signal.

Now, the next unity gain amp A3 sums up the A1 output (0 degrees) with A4 output (240 degrees), creating a 300 degree phase shifted signal at its pin#9, which is in turn inverted appropriately, shifting the phase to an extra 180 degrees, creating the intended 120 degree phase signal across its output indicated as "Phase2".

The circuit is intentionally wired up to work with a fixed frequency in order to yield better accuracy.

Fixed values are used for R1 and C1  for rendering the intended, accurate 60 degree phase shifts.

For specific customized frequencies, you may use the following formula:

R1 = (√3 x 10^6) / (2π x F x C)

R1 = (1.732 x 10^6) / (6.28 x F x C1)

where:
R1 is in kohms
C1 is in uf

Circuit Diagram



Parts List


All R = 10 kohms
A1---A4 = LM324
Supply = +/- 12vdc


Frequency (hz)R1 (kohms)C1 (nf)
10002.7100
4006.8100
604.71000
505.61000

The above design was investigated by Mr. Abu-Hafss and appropriately corrected for obtaining legitimate responses from the circuit, the following images provide a detailed info regarding the same:

Feedback from Mr. Abu-Hafss:

I needed a 15VAC 3-phase supply to test 3-phase rectifiers. I simulated this circuit the other day but failed to get proper results. Today, I made it work.

IC A2 and resistors connected to pin 6 could be eliminated. The resistor between pin 7 and 9 could be connected between the main input and pin 9. Phase-1 output can be collected from the original AC input. Phase 2 and 3 can be collected as indicated in the circuit.



However, my actual requirement could not be fulfilled. When these 3 phases are connected to a 3-phase rectifier, the wave form of phase 2 and 3 gets disturbed. I tried with the original circuit, in that case all three phases gets disturbed



Finally got a solution! A 100nF capacitor connected in series with each phase and the rectifier solved the problem to a great extent.

Though the rectified output is not consistent but, it is quite acceptable



Update: The following image shows a much simpler alternative for generating 3 phase signals with accuracy and without complicated adjustments:



Need Help? Please leave a comment, I'll get back soon with a reply!




Comments

  1. You are really helping . sir, Is it possible to convert car alternator to dc motor without PIC? if yes, I need your help on the circuitry. thank you

    ReplyDelete
  2. Thanks Musa, it is possible but it could be a mechanical concept, not within my expertise.

    ReplyDelete
  3. Thank you for the quick reply. I am a proud member of this blog. I can not wait to see the day passing without me visiting this site. I will try the mechanical concept, for the convertion of a car alternator to dc motor. Thank you once again.

    ReplyDelete
  4. You are welcome Musa, I appreciate your interest.

    ReplyDelete
  5. hi sir good day. I'm here again. i have a 3 phase genset(standby generator} i think it was rated 1.5-2kw 440v. My problem is i only need is 1 phase 220v output for my needs can you help me design a circuit to make it 1 phase output. Thank you for your effort of doing this.

    ReplyDelete
  6. Hi Edalcore,

    I am sorry I don't any verified approach to do this, so it might be dangerous to suggest something which hasn't been confirmed by me.

    ReplyDelete
  7. Dear edalcor zuproc!
    It is possible but only by using a transformer, if your generator has DELTA output, you would require a Delta-Wye Connection three phase transformer with a common neutral on its output to use it for single phase.. (Verified Method)
    You may ask for its calculations if you want to design it..!

    ReplyDelete
  8. Hello Swagatam Majumdar...!
    I need your kind help please, can you please provide me a frequency converter circuit to convert 220V 50 Hz to 220V 60 Hz for a load of about 5A at 220V using oscillations or any other method using MOSFETS or IGBT's.... please help me regarding this...!!!
    plz plz

    ReplyDelete
  9. Hello Muhammad Junaid,

    VFD is a very complex circuit, so I don't think it would be possible for me, I'll try though, if I succeed then will surely post it for you.

    ReplyDelete
  10. ..a single phase VFD looks slightly easier, I'll try to do it...let's be hopeful

    ReplyDelete
  11. Hi swatgatam Majumdar you are doing good job and i like your work it is very helpful for bigners or students

    ReplyDelete
  12. In your case there are 3 solutions one described by Mohammad junaid.
    2nd is to to 3 phase a.c. supply to d.c. supply then again converting it to single phase a.c. supply from d.c. but it is costly.
    3rd on is by replaceing old 3phse alternor with new one single phase alternator.
    may be 2nd solution is more costly by 1st or 3rd solution.
    but before thinking about implemention on any suggesion i advise you to download and read information about preinstalled 3 phase alternator may by its output winding is
    star ( Y ) conneted then there is a nutral or common terminal in its connection box.

    ReplyDelete
  13. Thank you very much sir,
    Now just how do we connect these three outputs transistors (MOSFETs) and then to a transformer to realize a usable three phase 380V phase to phase that can be used to power motors?

    ReplyDelete
  14. You will need the following circuits to implement it:

    https://homemade-circuits.com/2013/10/three-phase-inverter-circuit.html

    ReplyDelete
  15. 220V 50 Hz to 220V 60 Hz i would say just make from 220 AC --220 DC and after make half bridge mosfet or igbt pulsing on 60 Hz

    ReplyDelete
  16. use 3 phase rectifier and after let it pulsing on halfbridge mosfet or igbt

    ReplyDelete
  17. sir i had one doubt hw did u say the value of R=10Kohms

    ReplyDelete
  18. sir i would like to ask you one question??
    i have made a three phase detection circuit in which if the supply goes from RYB TO RBY the circuit detects and gives signal to the relay
    but i have one doubt
    how should i connect the three phase supply as an input to the circuit
    i can not connect directly
    i have to create a signal of it
    so how will i make that signal which is beyond my knowledge
    i can mail you my circuit through gmail
    my id is harshal.sharma055@gmail.com
    please help me

    ReplyDelete
  19. Hi Harshal, it's a bit tricky, I do not know the correct way of doing it, if i figure it out I'll inform you regarding it.

    ReplyDelete
  20. u have added me in google + so i can mail u the circuit of three phase detection circuit u can then help me out will it work or not ...

    ReplyDelete
  21. hey gud morning swagatam , i have made the three pulse generator , now its shown a single phase source as an input ,from where ill get this single phase source directly from the supply ??
    if yes , i did that the the 1st resistor burn out
    please help me

    ReplyDelete
  22. in the above circuit what will be the input source i mean what rating
    i used it with the230V SINGLE PHASE SUPPLY
    and the circuit burn out

    ReplyDelete
  23. Hi Harshal, since the circuit is 12V operated, the input should also be stepped down to 12V AC signal. You can do it by connecting a 0.1uF/400V capacitor in series with the input 10k resistor.

    THe outputs will then require half driver circuits to convert the relevant small signal phase shifts into 220V 3-phase AC.

    ReplyDelete
  24. hi swagatam , i m sharing a link from the google drive of the three phase detection circuit
    related to that i need ur help
    in tat circuit 3 phase input is needed
    so i m making a three phase signal using a three phase generator
    butwill it work>///?????
    link is
    https://drive.google.com/file/d/0B7f8SlTe2xORci1SbjMzcGN0LXM/edit?usp=sharing

    ReplyDelete
  25. i want to knoe more about this driver circuit is it an inverter circuit??

    ReplyDelete
  26. Sir,

    How do we generate -12V to connect to pin # 11. And I suppose all the numbers indicated on A1--A4 is the pin numbers of the respective IC.

    ReplyDelete
  27. Hi Harshal,

    Make the above circuit and confirm whether you are getting the 120 degrees phase shifts or not by applying a 12V sine AC at the input.....once it's confirmed you can use it with this circuit for the detection.

    you will need an oscilloscope for confirming this.

    ReplyDelete
  28. please refer to the last diagram given in the following link:

    https://homemade-circuits.com/2013/10/three-phase-inverter-circuit.html

    ReplyDelete
  29. Jagan, you will need a dual power supply for that, you can easily make a dual power supply by using a center tap transformer or by using a resistive network with a 24V single supply.

    Yes those indicate the IC pin numbers.

    ReplyDelete
  30. Jagan ull need to make a dual supply using a centered tapped transformer of 220/15 -0-15 V AND USING 7912 IC u can get -12 volt supply

    ReplyDelete
  31. hi swagatam, i m really thankful to you coz of ur quick response to me
    one last question i need to know the use of 0.1 microfarad 400v capacitor y to use it with the input?? is it necessary ??after using this capacitor should i hav to step down the voltage or i can directly connect the input to the supply

    ReplyDelete
  32. Hi Harshal,
    with a 0.1uF cap in series you can provide the supply from the mains directly, however it would be rather better to eliminate the capacitor and provide the input from a 0-12V transformer, this would kepp the circuit isolated and ensure safety from mains lethal voltages

    ReplyDelete
  33. Hey swagatam. I want to use this circuit for ac induction motor, please tell me if this circuit is working well. Also I want to know if anyone has build this circuit, thanks and please reply sooners

    ReplyDelete
  34. Emeka, you cannot use the above circuit directly with motor, you will have to employ a three phase driver circuit with it for operating the motor, please refer to the last circuit given in the following link:

    https://homemade-circuits.com/2013/10/three-phase-inverter-circuit.html

    ReplyDelete
  35. hi swagatam, i made the above circuit, its not working
    i m not getting a sinusoidal pulse as an output

    ReplyDelete
  36. also when i measure the voltage across capacitor with multimeter i m getting voltage of 12 v but its d.c. not a.c so now what to do??

    ReplyDelete
  37. Hi harshal,

    you will need an oscilloscope to confirm the outputs, there's no other method of confirming an AC sine output with 120 degree phase shifts.

    ReplyDelete
  38. i checked it swagat. but i m not getting a pure sine output also when i m measuring it with the multimeter the output i m getting voltages for both d.c .and a.c
    i saw harmonics in the output so couldnt measure the phase sequence
    please help me
    also the resistance value decreased from 10 K to 8.5 K
    so should i change the resistances???
    n how to give ground to that single phase source ??

    ReplyDelete
  39. do u have whatsapp messenger so that i can directly be in your contact this will also ease my time as my project dead time is last of april month
    ???my mobile no. is +918460285967
    harshal sharma

    ReplyDelete
  40. also i have shared a link previous a circuit of 3 phase phase detection circuit
    wich has 10v zener diode , so shold i change it to 5v zener diode???

    ReplyDelete
  41. i m trying to make a project which includes the controlling of elevator for 3 floor building, undervoltage and over voltage protection circuit and the three phase detection and protection circuit, well i hav made the controlling and o.v and u.v protection circuit but i am now stuck on this three phase detection and correction circuit??

    ReplyDelete
  42. In the meter it will only show RMS values, 12V in AC range and 6V in DC range.

    Actually the above circuit is not my design and I have not tested it practically, so it will be difficult for me to troubleshoot the circuit correctly.

    sorry I do not have a whatsapp account.

    ReplyDelete
  43. I'll try to find some other circuit which can create artificial 3-phase signals that you can use for confirming with your detector stage.

    ReplyDelete
  44. I haven't yet studied the circuit yet, if you can tell the role of the zener in the circuit then I can suggest whether it needs a change or not

    ReplyDelete
  45. what response did you get in the scope? Check the phase shift angle only, that's important...

    ReplyDelete
  46. the simplest method would be to take a small 3-phase motor and rotate it by coupling it to another motor (by belt or pulley)...once it starts rotating a three phase AC could be achieved across the three wires of the motor.

    ReplyDelete
  47. I need a 3 phase pure sine signal
    as an input for the three phase detection circuit
    also try to study my phase detection circuit
    it wil just take a matter of minutes
    4 u
    also the output of the above circuit is non sinusoidal
    but i need threephase pure sine

    ReplyDelete
  48. the zener diodes r just to clip odd the above unwanted waveform and make the sine wave lyk a square wave so it can be taken as a clock pulse

    ReplyDelete
  49. what kind of waveform are you seeing in the oscilloscope, across the three outputs of the above circuit??

    ReplyDelete
  50. hi swagatam, please i want to know if i can drive a three phase washing machine motor with your Three Phase Inverter Circuit and also i want the motor to run at 8000-12000 RPM

    ReplyDelete
  51. Hi Collins, yes it can be used for the motor but I am not sure regarding the RPM factor.

    ReplyDelete
  52. If I input a square wave with 30Hz, then after passing this circuit become 3 phase square wave? and will the frequency 30Hz changed???

    ReplyDelete
  53. yes it will be converted to a 3-phase square wave with 30Hz frequency

    ReplyDelete
  54. I checked d circuit 0 and 240 are fine but I'm not getting 120 properly on cro.
    I think drs prob in à3

    ReplyDelete
  55. 240V?? The input sine wave sample should not exceed the IC supply voltage which is 12V here....

    ReplyDelete
  56. hey.. is this possible convert 3 phase to 5vdc without transformer... and by using opamp..
    if yes please share ...

    ReplyDelete
  57. I have a pcb which convert 3 phase into 5vdc but i am weak in reverse engineering.. could you suggest me the simple way for tracing..

    ReplyDelete
  58. you can try this circuit:

    4.bp.blogspot.com/-MR2QAcISl4I/U9z3BuwZ6KI/AAAAAAAAHyw/e1IE6kxm8VA/s1600/3+phase+to+DC.png

    connect a 5V adapter such as a cell phone charger across the points "load" for getting the required 5V out

    ReplyDelete
  59. R1 = (1.732 x 106) / (6.28 x F x C1). Hello sir. Thanks for very useful info. From the formula, may i know what are 1.732, 106 and 6.28 represent for?

    ReplyDelete
  60. It was not explained in the original article, so not sure about them

    ReplyDelete
  61. ω = 2πƒ = 1.732/RC as (tan 60 = 1.732)

    R1 = (1.732 x 10^6) / (6.28 x F x C1)
    the unit of c1 is in nf

    the phase shift equation for rc circuit:
    Phase shift = arctan (2πfRC)

    ReplyDelete
  62. Will u pls post or mail the original article link

    ReplyDelete
  63. Hi Swagtam

    I needed a 15VAC 3-phase supply to test 3-phase rectifiers. I simulated this circuit the other day but failed to get proper results. Today, I made it work.

    IC A2 and resistors connected to pin 6 could be eliminated. The resistor between pin 7 and 9 could be connected between the main input and pin 9. Phase-1 output can be collected from the original AC input. Phase 2 and 3 can be collected as indicated in the circuit.

    https://dl.dropboxusercontent.com/u/20969135/Screenshot%202014-11-22%2000.58.38.png

    However, my actual requirement could not be fulfilled. When these 3 phases are connected to a 3-phase rectifier, the wave form of phase 2 and 3 gets disturbed. I tried with the original circuit, in that case all three phases gets disturbed :(

    https://dl.dropboxusercontent.com/u/20969135/Screenshot%202014-11-22%2001.00.40.png

    Any suggestions??

    ReplyDelete
  64. Just got a solution! A 100nF capacitor connected in series with each phase and the rectifier solved the problem to great extend.

    https://dl.dropboxusercontent.com/u/20969135/Screenshot%202014-11-22%2001.23.53.png

    Though the rectified output is not consistent but, it is quite acceptable.

    ReplyDelete
  65. Thank you Abu-Hafss,

    That's very impressive and this will be quite handy for all the readers out there who may be trying to build the above circuit successfully.
    I'll update the corrected images in the above article soon

    ReplyDelete
  66. Thanks for uploading my findings.

    However, this line

    "Though the rectified output is not consistent but, it is quite acceptable."

    should be mentioned at the end.

    ReplyDelete
  67. Hi Genius,
    I want a circuit that can convert single phase AC( 220v 15 amps 50-60 hz) to three phase 120 deg phase shift ( 440 v phase to phase 50-60 hz) that can run a 3hp induction motor.
    I am an Automation engg. from Mech. background and I have been looking for this circuit from a long time. it happens in VFD but they are too costly for the product that we are planning. Will really appreciate your help in it.

    ReplyDelete
  68. Thanks Debu,

    I have already published a few related circuits in this website, you can refer to those in the below given links, if you have problems understanding the concepts you can feel free to interact with me:

    https://homemade-circuits.com/2014/12/3-phase-vfd-circuit.html

    https://homemade-circuits.com/2013/10/three-phase-inverter-circuit.html

    ReplyDelete
  69. sir good day...sir have you design a much simple circuit for a single phase to three phase system...

    ReplyDelete
  70. you can refer to the following article:

    https://homemade-circuits.com/2014/12/3-phase-signal-generator-using.html

    ReplyDelete
  71. Dear Majumdar,

    what is the input value of the ac in the above circuit..? and how much will be the out put ac?
    Actually i need 3 phase 24 or 12V ac at60Hz out put. and i have 12 and 24 v ac 60Hz.

    ReplyDelete
  72. Dear Basheer,
    the output will be equal to the peak to peak value of the IC supply voltage, if the supply is 12-0-12V then the output will be also in accordance with this value,

    The input could also be equal to this value but not above this to avoid voltage clipping.

    ReplyDelete
  73. Hie swagatam plz can you help me build a three dc to ac inverter 48/240

    ReplyDelete
  74. Hi Adonis, I already have a 48V inverter circuit in this blog, do you want 3 separate inverters or tied up together.

    ReplyDelete
  75. the request
    sir,need pwm coding for three phase multilevel inverter @Swagatam Majumdar

    ReplyDelete
  76. sorry Basit, I have no idea about it....

    ReplyDelete
  77. Hello Mr. Majumdar, I would like to ask you how did you get the 60 degrees phase shift to sum up with the 240 degrees from A4? thanks for your time

    ReplyDelete
  78. Hello Rich This design is not mine, rather taken from another source, I have not yet investigated the calculations so far, so can't comment regrading it..

    ReplyDelete
  79. Oh ok, hehe. I have to check then. The thing is that I used this network for my work. Works fine and I understand all the process except that part I asked you.
    Thanks anyway for your time.

    ReplyDelete
  80. thanks for updating your experience!

    ReplyDelete
  81. Can I use Motor of 3-Phase Motor 2 HP with above sequence . ?

    ReplyDelete
  82. Hi Swagatam,

    Can the variable frequency signal [ from 1 to 60 Hz] circuit from timer 555 to feeds into its controlled board to run a salvage 3phase induction washer motor from 120VAC ?

    ReplyDelete
  83. Hi Cong, if you change the frequency in IC 555, it will also proportionately vary its PWM, it's better to use IC 4060 for getting a variable and perfect 50% duty cycle frequency...but the output will be a square wave which might not suit your induction motor

    ReplyDelete
  84. what software simulator you used to show the graph ?

    ReplyDelete
  85. Hi Amir
    The software is LT Spice IV, it free to download at www.linear.com/designtools/software/

    ReplyDelete
  86. Hello. for the updated circuit, could you tell me what the resistance and capacitance is to make the 50 Hz frequency? And how to change the frequency with the resistance?

    ReplyDelete
  87. Hello, I assume that it is originally calculated for 50Hz, nonetheless you can practically test it and tweak the results if required by changing the R or C values accordingly...

    ReplyDelete
  88. Hi,

    We have connected the circuit as given in picture3 as done by Mr. Abu-Hafss.

    The output for 120degree is not coming , it is only 60degree phase shift. for obtaining 120 degree phase shift i had to connect one more RC circuit at the output of U3. please help with this.

    Please explain the working of the summer used.

    Also, what is the value (1.732*106) is the equation, R1 = (1.732 x 106) / (6.28 x F x C1)

    Thank you in Advance.
    Chaithra

    ReplyDelete
  89. Hi, This circuit was referred from another article long ago and not designed by me, therefore regarding the circuit functioning I won't be able to suggest much.

    Regarding the formula, I have updated it in the article with more details. Most of the variables in it are constants.

    ReplyDelete

Post a Comment