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How to Make a 3 Phase VFD Circuit

How to Make a 3 Phase VFD Circuit

The presented 3 phase VFD circuit (designed by me) can be used for controlling the speed of any three phase brushed AC motor or even a brushless AC motor. The idea was requested by Mr. Tom

Using the VFD

The proposed 3-phase VFD circuit can be universally applied for most 3-phase AC motors where the regulation efficiency is not too critical.

It can be specifically used for controlling squirrel cage induction motor speed with an open loop mode, and possibly also in the closed loop mode which will be discussed in the later part of the article.

Modules Required for 3 Phase Inverter

For designing the proposed 3 phase VFD or variable frequency drive circuit the following fundamental circuit stages are essentially required:

  1. PWM voltage controller circuit
  2. 3 phase high side/low side H-bridge driver circuit
  3. 3 Phase generator circuit
  4. Voltage to frequency converter circuit for generating V/Hz parameter.

Let's learn the functioning details of the above stages with the help of the following explanation:

A simple PWM voltage controller circuit can be witnessed in the diagram given below:

 The PWM Controller

I have already incorporated and explained the functioning of the above PWM generator stage which is basically designed for generating a varying PWM output across pin3 of IC2 in response to the potential applied at pin5 of the same IC.

The 1K preset shown in the diagram is the RMS control knob, which may be appropriately adjusted for acquiring the desired proportionate amount of output voltage in the form of PWMs at pin3 of IC2 for further processing. This is set to produce a corresponding output that may be equivalent to the mains 220V or 120V AC RMS.

The H-Bridge Driver Circuit

The next diagram below shows a single chip H-bridge 3 phase driver circuit using the IC IRS2330.

The design looks straightforward as most of the complexities are handled by the chips in-built sophisticated circuitry.

A well calculated 3 phase signal is applied across the HIN1/2/3 and LIN1/2/3 inputs of the IC through a 3 phase signal generator stage.

The outputs of the IC IRS2330 can be seen integrated with 6 mosfets or IGBTs bridge network, whose drains are appropriately configured with the motor which needs to be controlled.

The low side mosfet/IGBT gates are integrated with the IC2 pin#3 of the above discussed PWM generator circuit stage for initiating the PWM injection into the bridge mosfet stage. This regulation ultimately helps the motor to gain the desired speed as per the settings (via the 1 k preset in the first diagram).

3 phase VFD manual

In the following diagram we visualize the required 3 phase signal generator circuit.

Configuring the 3-Phase Generator Circuit

The 3 phase generator is constructed around a couple of CMOS chips CD4035 and CD4009 which generates accurately dimensioned 3 phase signals across the shown pinouts.

The frequency of the 3 phase signals depends on the fed input clocks which should be 6 times the intended 3 phase signal. Meaning, if the required 3 phase frequency is 50 Hz, the input clock should be 50 x 6 = 300 Hz.

It also implies that the above clocks could be varied in order to vary the effective frequency of the driver IC which in turn would be responsible of varying the motor operational frequency.

However since the above frequency alteration needs to be automatic in response to the varying voltage, a voltage to frequency converter becomes essential. The next stage discusses a simple accurate voltage to frequency converter circuit for the required implementation.

How to Create a Constant V/F Ratio

Typically in induction motors, in order to maintain an optimal efficiency of the motor speed and toque, the slip speed or the rotor speed needs to be controlled which in turn becomes possible by maintaining a constant V/Hz ratio. Since the stator magnetic flux is always constant regardless of the input supply frequency, the rotor speed becomes easily controllable by maintaining the V/Hz ratio constant.

In an open loop mode, this can be done roughly by maintaining predetermined V/Hz ratios, and implementing it manually. For example in the first diagram this may be done by suitably adjusting the R1 and the 1K preset. R1 determines the frequency and the 1K adjusts the RMS of the output, therefore by suitably adjusting the two parameters we can enforce the required amount V/Hz manually.

However to get a relatively accurate control of an induction motor torque and speed, we have to implement a closed loop strategy, wherein the slip speed data needs to be fed to the processing circuit for an automatic adjustment of the V/Hz ratio so that this value always remains near about constant.

Implementing the Closed Loop Feedback

The first diagram on this page can be suitably modified for designing the closed loop automatic V/Hz regulation as shown below:

In the above figure, the potential at pin#5 of IC2 determines the width of the SPWM which is generated at pin#3 of the same IC. The SPWM are generated by comparing the mains 12V ripple sample at pin#5 with triangle wave at pin#7 of IC2, and this is fed to the low side mosfets for the motor control.

Initially this SPWM is set at some adjusted level (using 1K perset) which triggers the low side IGBT gates of the 3-phase bridge for initiating the rotor movement at the specified nominal speed level.

As soon the rotor  rotor begins rotating, the attached tachometer with the rotor mechanism causes an proportional additional amount of voltage to develop at pin#5 of IC2, this proportionately causes the SPWMs to get wider causing more voltage to the stator coils of the motor. This causes further increase in the rotor speed causing more voltage at pin#5 of IC2, and this goes on until the SPWM equivalent voltage is no longer able to increase and the stator rotor synchronization attains a steady-state.

The above procedure goes on self adjusting throughout the operational periods of the motor.

How to Make and Integrate the Tachometer

A simple tachometer design can be seen in the following diagram, this could be integrated with the rotor mechanism such the rotational frequency is able to feed the base of the BC547.

Here the rotor speed data is collected from a hall effect sensor or a IR LED/Sensor network and is fed to the base of T1.

T1 oscillates at this frequency and activates the tachometer circuit made by appropriately configuring an IC 555 monostable circuit.

The output from the above tachometer varies proportionately in response to the input frequency at the base of T1.

As the frequency rises the voltage at the extreme right side D3 output also rises and vice versa, and helps to keep the V/Hz ratio to a relatively constant level.

How to Control Speed

The speed of motor using constant V/F can be achieved by altering the frequency input at the clock input of IC 4035. This can be achieved by feeding a variable frequency from a IC 555 astable circuit or any standard astable circuit to the clock input of IC 4035.

Changing the frequency effectively changes the operating frequency of the motor which correspondingly lowers the slip speed.

This is detected by the tachometer, and the tachometer proportionately reduces the potential at pin#5 of the IC2 which in turn proportionately reduces the SPWM content on the motor, and consequently the voltage for the motor is reduced, ensuring motor speed variation with the correct required V/F ratio.

A Homemade V to F Converter

In the above voltage to frequency converter circuit a IC 4060 is used and its frequency dependent resistance is influenced through a LED/LDR assembly for the intended conversions.

The LED/LDR assembly is sealed inside a light proof box, and the LDR is positioned across a 1M frequency dependent resistor of the IC.

Since the LDR/LDR response is fairly linear, the varying illumination of the LED on the LDR generates a proportionately varying (increasing or decreasing) frequency across pin3 of the IC.

The FSD or the V/Hz range of the stage could be set by appropriately setting up the 1M resistor or even the C1 value.

The LED is voltage is derived and illuminated through the PWMs from the first PWM circuit stage. It implies that as the PWMs vary, the LED illumination will also vary which in turn would give rise to a proportionately increasing or decreasing frequency at pin3 of the IC 4060 in the above diagram.

Integrating the Converter with VFD

This varying frequency from the IC 4060 now simply needs to be integrated with the 3 phase generator IC CD4035 clock input.

The above stages form the main ingredients for making a 3 phase VFD circuit.

Now, it would be important to discuss regarding the DC BUS required for supplying the IGBT motor controllers and the setting up procedures for the entire design.

The DC BUS applied across the IGBT H-bridge rails may be obtained by rectifying the available 3 phase mains input using the following circuit configuration. The IGBT DC BUS rails are connected across the points indicated as "load"

For a single phase source the rectification may be implemented using standard 4 diode bridge network configuration.

How to Set Up the proposed 3 phase VFD circuit

It may be done as per the following instructions:

After applying the DC bus voltage across the IGBTs (without the motor connected) adjust the PWM 1k preset until the voltage across the rails become equal to the intended motor voltage specs.

Next adjust the IC 4060 1M preset in order to adjust any of IC IRS2330 inputs to the required correct frequency level as per the given motor specifications.

After the above procedures are completed, the specified motor may be connected and supplied with different voltage levels, V/Hz parameter and confirmed for an automatic V/Hz operations over the connected motor.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

210 thoughts on “How to Make a 3 Phase VFD Circuit”

  1. hi dear,
    pls find this link. here it has been shown SPWM with micro-controller. But it can not control PWM frequency. for this reason i could not make that. i hope you will find any technique to control this circuit. please try to do that.


  2. hlw sir, i want to use ir2110 driver ic .that means i will create 3 phase bridge with 3nos ir2110 ic. because our local market didn’t sell that ic (irs2330). please tell me if i use that driver ic what will happen? can i use it prperly.

  3. Hello sir,
    This is very good idea. can u please tell me about PWM and SPWM and Which is the better between PWM and SPWM.


      • Thanks sir, is this possible to making SPWM signal without micro-controller ? Please tell me, can i control the motor from 1hz to 50hz using your VFD circuit.

        • Hi Milon, SPWM is not related to frequency control, it is for creating a sinewave output. You can control frequency by adjusting R1 in the IC 555 circuit

            • thanks sir, actually i want to make your VFD circuit. My induction motor capacity is 0.5hp 3-phase. actually you are the professional at this sector.please suggest me, what i should? just i want to control frequency of this motor also RPM without any problem. frequency control means rpm automatic controlled. that means i want to control 1hz to 50hz only.for testing purpose i will use digital frq meter….please tell me is it possible..

            • Hi Milon, it is possible to control the motor using the above idea, however the concept may not be easy for a newcomer, or a less experienced person.

              There’s perhaps an easier method using a bidirectional switch concept. I will try try to update it soon, which you can try.

  4. Hola señor. Un verdadero placer encontrar tanta información, desde ya muchas gracias por su atención.
    Hace tiempo estoy intentando realizar mi motocicleta eléctrica y debido a políticas de importación, me es muy difícil adquirir motor y demás.
    Logre convertir un alternador en motor con 3 fases y alimentación de escobillas con poca tensión. Mi pregunta es, este circuito me sirve para eso?. Creo que los componentes electrónicos puedo conseguirlos.
    Una vez más GRACIAS. atte Raúl.

    • Gracias Raul, es un placer para mí también! Sí, puedes usar el segundo circuito para controlar la velocidad a través del potenciómetro 1K. Dado que un alternador no es un motor de inducción, el control de V / Hz puede no ser esencial, y puede implementar el control de velocidad utilizando el método PWM.

  5. good day sir, i know the reason why the gate driver ic produce heat, when i tested it, at first the gate driver ic have a normal temperature but when i start to vary the pwm voltage controller to its minimun value, the driver ic start to produce heat, my guess is that the excess voltage that have been reduce by pwm voltage controller return to gate driver ic as a result the ic produce excessive heat. from your point of view sir swagatam is my theory is right? thanks for responding in advanced.

    • yes that may be possible, that’s why it is important to include the BJT buffer stage so that a high value resistor can be used at the base, which can stop the reverse entry of the PWMs

      • Hello sir ,how you?
        I have work out your inverter circuit sir . It’s awesome.
        some time the IGBT gets short circuited. I have used the IGBT FGA25N120ANT and the load is about 7.5 hp415v .
        In inverters ,is the pwm used for regulating the output rms voltage ? If that so why do we regulate that in the input DC bus.
        Reply me sir ,pwm is must or not ?why it is used in inverters?

        • Thank you Sageyu, yes that’s quite right PWM determines the RMS of the output and also the waveform of the output AC. Regulating it at the DC side becomes more convenient than on the AC side, which would otherwise require special devices and configurations.

    • I am not sure at what voltage the ITRIP is designed to trip…you can refer to the datasheet of the IC and find this value.

      Once you find it, you can multiply this value with the maximum safe current limit of the load…this will give you the wattage rating of the resistance…subsequently you can also calculate the resistance value applying this ITRIP voltage with Ohm’s law

    • dave, if your IGBTs burnt, your mosfet would also probably burn…you must first a build small model of it using BJTs such MJE13005 and check whether your basic circuit is working correctly or not, if it does only then you must go ahead with higher alternative devices.

  6. good day again sir swagatam, we follow all the process, when we test it, we supply 3phase, and after we supply the positive dc rail and negative dc rail become shorted, then the gate driver ic become hot and it do not produce the right output, from your point of view what happen?)

    • please confirm the 3 phase signal with a scope, if possible please show me the image of the waveform to understand the situation….if applying Vcc supply to the full bridge iC is causing a short circuit that means your IC is faulty.

  7. Good Day Sir, how will the pwm voltage controller vary the output voltage of the inverter circuit? can you explain it to me because i am so confused on how the circuit works. thank for responding to dumb question

    • Dave, the PWM will chop the low side mosfet conduction and force the load to conduct as per the average conduction rate of the applied PWM and in this way control the power of the load and its operational rate

  8. Good day sir, where will i connect the ground of the gate driver ic? Is it in the same source of other circuit like 3phase gen and etc. And for confirmation is the negative dc bus is connected to the ground of gate driver ic?

    • Hi Dave, all the ground connections should be joined in common, meaning all the negatives, from DC BUS and the circuit DC should be joined together as common.

  9. Hai sir, I have almost done with first three circuit of 3 phase VFD , but i have small problem that IRS2330 IC or IRS2332 IC that is in last circuit before igbt bridge is not available here in our location so plz instead of that IC which can use for this circuit

    • Hi Shivaji,
      The full bridge IC is the heart of the circuit.
      you should have started only after procuring all the parts, if you don’t get the full bridge IC now, your 3 circuits will be wasted.

      You can inquire with your local part dealer regarding any other full-bridge driver IC, or H-bridge driver IC option?

      But before buying the full bridge IC it would be better if you first confirm the 3 circuits that you have built and make sure you succeed with it first.

      • hai sir, plz can i know what output pins of PWM voltage controller circuit should connect the voltage to frequency converter circuit ( pwm inputs)

          • HAI SIR, i got output from first pwm ckt from 50hz to 160hz frequency by varying 1k preset is it correct output sir. and i connected it to ic4060 ckt then i got clock pulse with time period 4.7sec and 209mhz freq.

            • Hi Shivaji, yes 50Hz-160Hz looks OK, but 209 MHz is not OK.

              first confirm the 4060 output frequency without the PWM integration….and also check the LED/LDR assembly separately before connecting it with the 4060 IC, check whether the LDR resistance is changing proportionately with the PWM or not.

          • sir, i cross checked the terminal outputs of 4060ic wtout pwm input and i got same 114v mean value to 70v mean without any frequency value .

            With pwm input i got output as 203Mhz with square pulse.

            • Shivaji, 4060 works on DC and its output will be in DC not in AC and not in such high level.

              This circuit is suitable only for the advanced and expert electronic hobbyists and engineers, please attempt this only if you are completely aware of what you are doing…

          • Good day sir ,i apologize for such mistakes . i doing my master degree in power electronics and i am trying to publish it as my project if i done with this . so plz help me sir . plz give your mail id and i will send all my ckt connection diagram.

            • Hi Shivaji, since you are doing your maters degree you will know for example, that a CMOS IC cannot generate 170V at its output, right? so these are small things you must be well versed with. It will be difficult for me to explain all the small basic things regarding of the above circuit operation.

              If you have any specific questions regarding a particular component or stage then I can help, but not regarding every small things, you will have to first learn how a 4060 IC operates… how the other mentioned ICs in the circuit operate, only then you will be able to grasp the working of the above concept…

  10. Good day sir, can i put 1k resistor value to the 6 resistor that is connected to the output pins of the ic4049 at the 3 phase generator circuit?

    Another question sir, if I use polarized capacitor to replaced the 1uF 25V capacitor at the output pin of the igbt , where will I connect the positive pin of capacitor, is it at the output or at the VB pin of the Gate driver IC

    • Good day Dave, it does not matter whether you connect a resistor or not because the HIN, LIN inputs are CMOS based and have infinite input impedance so the presence or absence of resistors do not matter.
      I would not recommend polarized capacitor because I am not sure how they work with the IC pinouts, so better to use a non-polar type.

      The VB1/2/3 all will go the respective IC pinouts marked VB1/2/3… which are also connected with the cathodes of BA159 diodes.

  11. Good Day Sir Swagatam, thank for the responds for all of my question,

    Sir can you explain the voltage to frequency converter circuit, is it suppose to construct the circuit as the diagram indicated, can i leave the other pin of ic 4060 hanging?

    • Hi Uday, both have used the same principle of driving a 555 IC in the PWM mode by applying a square wave at its pin#2 and a modulating wave at its pin#5

  12. Sir, In my application I am restricted to use 48V DC battery for the DC bus.
    Now, I need to run an induction motor at speeds ranging from 400RPM to 800RPM.
    So can I get 120V AC (or even higher than that) across the inverter with 48V DC as input?


    • Uday, you can use a 3 phase transformer across the 6 mosfets (IGBTS), and convert the 48V into the required 120V AC through it…

  13. Hi Swagatham,

    I connected 3 phase generator circuit as per your diagram and fed the gating signals to the driver. Initially the motor ran with very low speed, if I try to increase the frequency of the clock, then the motor stalls(making some noise when frequency is increased). Can you help me in debugging the circuit? What modification do I need to do to make the motor run for higher speeds? I know its tough to tell like this, but any guess is appreciated.


    • Hi Uday,

      if you increase or decrease the frequency, it could damage the motor, the frequency should be exactly as per the motor's recommended specifications, and make sure the input 3 phase signal is 120 degrees apart, please confirm these parameters first before applying it to the main driver IC.

      you must verify the 3 phase generator output first….

      if you have difficulty with the 3 phase generator explained in the above circuit, you can use the one which is explained in the following article


    • Yes Sir, I have checked the output of the 3 phase generator. It is doing its job as it is supposed to be. And the motor is rated to operate at 400Hz, but it is unable to run for some reason.

      Thanks for your response

    • Uday, please check the peak voltage and RMS voltage across the output terminals without connecting the motor and after connecting the motor.

    • Hi Sir, I am grateful for your contribution. The motor is now running. However I am confused about PWM Voltage Controller circuit.


      1. When you say "set PWM voltage controller circuit to produce a corresponding output that may be equivalent to the mains 220V or 120V AC RMS", How come a 12VDC input circuit produces that much AC voltage? (Apologies if the question is too dumb).
      2. Can we integrate the DC bus voltage with the frequency converter circuit, so that if we vary DC bus voltage linearly, it increases the frequency maintaining constant V/Hz ratio.

      Thanks in advance

    • You are welcome Uday!

      The PWMs are at 12V level, but it's controlling the gate of the mosfets, which in turn is causing the mains DC BUS voltage at their drains to get chopped in the same ratio, resulting in a proportionately reduced 220V AC, this value can be increased or decreased by varying the PWM duty cycle proportionately…I hope you know how PWM duty cycles work, right?

      your second question will need to be investigated before answering…

    • Great Sir, I think I got what you are saying!
      I don't know in candid about the PWM duty cycle concept. But I will look into it for deeper understanding. Appreciate if you provide any link to understand that!

      And Sir, what happens if we vary the duty cycle of the clock by some means?
      As always thanks for your time Sir!


    • if you vary the duty cycle of the clock that will also result in a proportionately reduced AC mains at the mosfet drains

    • No… sorry it won't have any effect, because the clocks are being converted to triangle waves which is compared with the pin#5 potential…but since the clock frequency has no relevance to the triangle wave height, it won't affect the PWM waveform in any manner

  14. One more Sir,

    The outputs from IC 4049 should be inverted?
    Since the driver pins has bar over (-ve logic) for HIN and LIN


    • it can be left unused and configured as indicated in the diagram, these are actually the pinouts of an extra internal opamp which could be used for switching an external parameter if required, otherwise it could be simply left unused

  15. Hi Swagatham,

    Fabulous idea of integrating the V/Hz parameters.
    However I have one question, the PWM voltage signals are only connected to low side MOSFET gates, why they are not required for High side gates, Can you throw some light on this please?


    • Thanks Uday,

      the low side mosfet PWM chopping is sufficient for achieving the required RMS control and sine wave equivalent waveform at the output, because the current from the high side mosfet cannot reach the load unless it passes through the low side mosfet, and during this process the current has to go through the injected low side PWM chopping at any cost, before it can reach the load, therefore only a low side switching is good enough and does the job…

    • Thanks for sharing your knowledge, I am learning step by step.
      Have you implemented this circuit in reality?
      I am connecting it as per your circuit diagram.

      Question: What will be the outputs across the HO1, HO2, HO3 and LO1, LO2, LO3 pins of the driver without connecting the MOSFETS? Since I want to confirm the proper outputs of the driver before I feed them to the MOSFETS.


    • I have designed the circuit after doing an intense research of all the details of the IC pinouts, as mentioned in the datasheet of the IC.

      Outputs of any logic IC can remain open if required, it will never affect the IC in any manner.

      by the way here for HO1—-HO3 and LO1—-Lo3 all are supposed to be connected with the gates of the respective power devices through low value resistors as indicated in the diagram

  16. Hello sir as you discussed about 3 Phase Variable Frequency Drive Circuit
    In IRS2330 instead of it Can I use IR2110 – 3 ICs to drive 6 Mosfet 2N60. Individually 2 MOSFETs by one IC IR2110.

  17. Hi. This is the answer that I want. I am in the project to control the pumps in the plastic industry. Is it applicable for the pump that has ac power above 3 KW? Thank you.

  18. Hi,

    Nice job!, keep it going!

    I wanted to ask something, not that off-topic after all.

    I've been reading for a time already about squirrel-cage and blcd's, and I'm just a bit puzzled about power ratings (consumed vs. delivered).

    I've read blcd's offer a higher size/power ratio than asynchronous ac induction motors, overall outrunners, so my question is:

    Does this mean that, say, a small hobbyking's donkey brushless outrunner (14.8V – 680W) can develop more or less the same (or even more) torque than a bulky 3/4 hp (750W) 3-phase squirrel-cage motor?

    I'd really appreciate if somebody could clear this one up for me.

    Thanks so much,


    • Hi thanks for your interesting question, however I have not yet investigated motors deeply so I am presently quite clueless…possibly Ill do some research, and hopefully update the answer here…

  19. Hello Sir, I have a few questions regarding the circuits above;

    1. Can you suggest the suitable IGBT that should be used for a 1HP 3Phase motor?

    2. Is it possible for me to use ARDUINO as the PWM controller?

    I'm currently on a project that needs to create a system that may control and monitor the type of motor I've stated above,by using ARDUINO. Please advise, Sir.

    Thank You.

    • Hello Zuleikha,
      1) You can try STGW10M65DF2 or similar

      2) If you have a 3 phase signal generator using Arduino, then definitely you can use it with the full bridge driver IC LIN, HIN pinouts

      you can link the SD pinout of the driver IC with your Arduino feedback control and achieve the desired control on the motor

    • according to me the mentioned will work, but it would be better if you confirm it yourself through the datasheet of the device.

  20. Thank you sir for the quick response. Am grateful. Please sir sorry to bother you again. I would have actually mentioned this from the onset but I forgot. The alternator is a 3 phase alternator with star winding on the stator. So do you insist I make use of the pwm based motor circuit as you advised, considering the fact that it has 3 phase winding or is there a way I can work through this either with a different circuit or better still the pwm based motor circuit. Thanks.

  21. Goodday sir, I really want to commend your efforts. More grease to your elbows sir. I have looked at the circuits above and I really appreciate you for them. I am currently working on a project where I will have to convert a car alternator to a brushless DC motor with speed control. I have not been able to get an ESC because I live in a very remote area in Nigeria, so I really think your circuit would be of great help to me. But I actually have a little problem with understanding the various connections and how or where to connect them. First is the pwm voltage controller circuit, where do I connect the other pin from the 1k preset variable resistor I.e the pin with a plus (+) sign. Secondly, are the pins labelled fault and cao from the irs2330 to be left just like that without connecting anything to it? Thirdly, in the 3 phase signal generator circuit you made use of ic4009 and you also made mention of ic4049, but sir when I checked the pinout for these ICS online, I noticed that they had 16 pins each. Pls sir how do I go about this? I couldn't really figure out how to connect them as shown in your circuit. Lastly sir, on the frequency converter circuit where do i connect the pwm input and 0v. I initially thought that the 0v was the ground but I later saw the ground at the top, just after the capacitor. Sir pls I would be most grateful to have all these explanations I really need it for the sake of this project and any suggestions you may have is highly welcomed. Thanks a million.

    • Thanks Andrew,

      VFDs are actually used for controlling AC motors which operate on mains voltages, for DC motor application the above complicated theory may not be required.
      You can simple use the first circuit from above and use it with your alternator. You will need to connect a mosfet at pin#3 of IC2, and connect the motor across its drain and the positive supply…after this, varying the 1K pot will enable you to achieve the required speed control of the motor.

      alternatively you can also try the following concept for the same:


  22. Hi
    i am omkar pawaskar from Goa
    i want to make Variable frequency drive to control 3 phase Induction motor on batteries

  23. hi sir, i have complete my cct but when i connect the single phase to measure the o/p , the 555 timer ic 1 and 2 got burned plz tell me what i should i do

    • Hi Muhammad, you must complete each stage separately, test them separately, confirm them separately and then gradually integrate them for the final results….if you make the whole thing at once it won't work or might cause unexpected results

  24. hi dear swagatam i want to build 3 phase inverter with 220 volt singlr phase(actually 1 phase to 3 phase inverter) i have some question to you, first of all thank you for your sharing your knowledge,first question that is , can we use sg 3525a ic for input clock of cd4035a insted of 4060 ic? and why we use 2 555 ic for low mosfet's or igbt's whereas the IR 2330 have 6 output and 3 of this output for low igbt's, i mean are we must conect the output of ic2 555 pin 3 to IR 2330 low igbt's signals?what is that mean? and the other is how can we generate 6 pulse from cd 4049 ic?i mean can you show the connection the 3 output of cd 4035a to 4049?and can we use cd 4009 instead of cd4049?

  25. Good day sir 🙂 as I connected the pwm generator to voltage/frequency converter the LED tends to not vary its illumination. it has a constant illumination and the 1K potentiometer seems to be its switch to turn onandoff the LED, may I ask sir to what IC ouput should specifically be inputted to the pwm inputs of the LED?

    And also sir, should the frequency on the IC4060 should be square wave?

    • Goodday Johnny, that means your PWM circuit is not working correctly.

      first check frequency at pin#3 of IC1, make sure it's generating square waves at a frequency rate depending on R1 value, may be around 100 Hz or 150Hz, then you can confirm further the pin#3 response, check voltage here by varying the 1K pot….the voltage should also vary from 0 to 8V, for a supply voltage of 12V.

  26. hy sir
    please tell me the values of capacitors which are connected to the igbt and also tell the value of the capacitors which are connected to irs2330

  27. Hy sir,
    so sir my IC1 and IC2 circuit functional and i have seen the waveform on the CRO.Nw i connect the Cd4035 clock on pin number 6 so tell me which circuit give me clock pulse for CD4035 and also tell me that if i connect Low side of mosfet to IC2 pin number 3 then i will be not needed to connect IRS2330 LO1.Lo2.Lo3 output to low side of MOSFET.

    • Hi Muhammed, connect the frequency pin of 4035 with pin#3 of IC1, and make sure the IC1 is adjusted to generate frequency at the rate of 300Hz.

      the low side mosfets should be connected with pin#3 of IC2 via isolating diodes as indicated,

      No, the "LIN" inputs of the driver IC does not need to be connected with pin#3 of IC2

  28. hy,
    there is any resistor connection between IC2 o/p to CD4035 and Cd4035 o/p to CD4009 and CD4009 o/p to CD4049 and CD 4049 o/p to IR2130 for dropping the voltage level from one IC to the Other IC.
    And I use IR2130 instead to IRS2330. Is this right Choice in this circuit ???

    And also Tell me that optoisolator LED/LDR is not available in the market Am is use another optoisolator like as PC817??

    • Hi, IC2 is not connected with 4035, IC2 is connected with the low side mosfet gates without any resistors.

      CMOS inputs don't require resistors as they have high input impedance so resistors are not involved with the shown 40XX ICs and their i/p, o/p terminals.

    • please don't make the opto coupler based circuit as yet, first confirm the first two circuit operations if you succeed then later you can think about building the 4060 stage.

  29. Hy
    i make this circuit bt ckt have some problem ,
    Firstly o/p of 555 ic2 is squire wave form on the CRO bt when i check the o/p of CD4035 then there is no o/p on pin1,15,14.CRO show only single line and there is no wave form bt when i disconnect the gound pin 8 of cd4035 the CRO o/p show like as input.
    Please tell me that what is the problem in my circuit that no show o/p on CRO.

    • Hi, the 4035 circuit is a single phase frequency to 3 phase frequency converter circuit which I got from internet after some searching, I am not sure regarding its working principle, you may have to consult its datasheet for the details, or try some other design which can replicate its function for this project.

    • Thanks alot sir.Pls tell me 1)why 3 diodes connected between op of PWM generatorpin (3) and lower MOSFETS gates ? 2) Actually lower MOSFETS gates are driven by IRS2330,is it rite?

  30. Hi Swagatam, It seem any image won't be able embed in this reply box. Is there alternative way to do so? I did captured 2 wave form images for you views and make some input.


    • Hi Cong, you can send it here


      By the way if you are getting a square waveform then your 555 IC is working correctly….anyhow you should first confirm what exactly your control board requires for the processing of the motor control….until you know the exact specifications I don't think the experiment would make any sense

  31. Hi Swagatam,

    I have attached 2 images with the square wave form captured, one set at 7Hz and 34Hz the other. I don't know what i'd missed
    at the first shot; the motor did not run at all. The controlled board was in good shape before the washer dismantled. I'll double check the control board as needs.
    The Fq. generator build from timer 555. I'll do a new circuit with IC either 4047 or 4060 per your suggestion.

    Thank you in advance.

    I not sure how to attache the image. c&p function the 2 above lines.

  32. Hi Swagatam, Additional question; Is that true if the variable frequency signal output from IC 4060 or 4070 prototype be able to substitute the software signal as seen in that video clip? I'd heard someone had said NO! What your though? Thank you in advance.

    • Cong, if the waveform is an ordinary square wave then definitely any variable square wave frequency will work as good as the arduino source…if you can show me the waveform of the input then I can confirm my suggestion

  33. Hi Swagatam, Thank you so much for your prompted respond my question. When i came across on the net and had seen a short video clip from " https://www.youtube.com/watch?v=Npxd_H7FeSQ " run the same washer motor and the controlled board as mine with his laptop; I then think about a timer 555 circuit [can generate from 1 to 60 Hz], with a 5Vcc to pin 1, an output of the timer to IO pin 2, and GND to pin 3 of the controlled board as seen as those 3 blue wires in the video clip. One thing i am missing is an amplitude of the signal. And of course, i haven't get any luck at all. Please help if you would

    • Thanks Cong, I can't say much about IC 555 in the mode which you have suggested, but if you are looking for a good variable 1 to 60Hz frequency with a fixed duty cycle then IC 4060 should be the best choice according to me.

  34. Can a dual 555 timer circuit on the top page be able to feeds to the 3 pin [ GND, I/O, and VCC pins] input connector of the controlled board will run a good salvage washer 3 inductor motor VFD from 120VAC?

  35. Good day sir. May I ask, am I going to connect the pwm generator directly to the pwm input of the clock generator? or is it directly connected to the driver ic? or is it that the IC4049 is the one connected to the driver IC? and also what is the ouput frequency of the PWM generator, Clock generator and Signal generator. I am currently studying this circuit for a proposal device

    • The first design is the PWM generator circuit, whose output needs to be fed to the gates of the low side mosfet.
      the second circuit is the mosfet full bridge driver circuit which receives its 3 phase signal from IC 4049 buffer stage.

      THe 4049 buffer stages receive the relevant inputs from the 3-phase generator IC 4035.

      IC 4035 receives the clocks from either IC1 (555) from the first design or it could be integrated with the output of 4060 IC as shown in the last design for an automatic regulation

  36. the frequency can be adjusted by varing R1, it should be around 200Hz.

    how would you get 3 HIN, and 3 LIN for the IC IRS2330 with a IC 555 at 120 phase shift?? not possible

  37. Thanks for your reply. I want to control the speed of three phase motor with controller and from a single phase (240 volts)(actually convert single phase to 3 phase). i need your guidance to complete this project. i make simple pwm with variable frequency from pic controller like 50Hz -100Hz. Then i apply this pwm to 4035 circuit so that i got 3 pwms with 120 deg difference from 4009 i got 6 pwms according to your circuit. Now i am going to attached IR2110 3 phase mosfet drive circuit with 6 pwms according to your circuit.
    Now my question is that is these pwm's is good for IR2110 to drive IRF840 the positive DC volts of IRF840 is 240 volts single phase.

    • The 3 phase driver IC is IRS2330, not IR2110…you may have to use 3nos of IR2110 circuits if you are this IC…. the IRS2330 has been configured exactly as per its datasheet instructions, and it is designed to accept the 120 phase shift square wave from a given source….so everything's fine in the diagram…but you will need to confirm all the stages separately and by using a low voltage at the mosfet side initially

      yes IRF840 can be driven with the above discussed ICs

    • 1.Are the capacitors 1uF 25V are polar capacitors or non polar capacitor(H bridge driver circuit)?

      2. Diode values or number that are connected across the IGBT s ?

      3. Can we use a Axial fuse in place of that 1ohm 40 watt resistance

    • 1) 1uF can be polar or non-polar does not make any difference.

      2) diodes are internally present in the IGBTs, no need to connect from outside

      3) 1ohm is the current sensing resistor it cannot be replaced by a fuse.

    • Swagatam whats is the explanation that there will be no single phasing in the Induction motor.As i dont find any relation or synchronization between the signal generator and PWM regulator circuit.

      I dont understand that.

    • Sorry, I could not understand your question properly. this is an artificially created 3 phase driver circuit which will never cause single phasing as long as the devices are working correctly.

      the PWM is specifically for adjusting the RMS voltage while the signal generator is for generating the required 3 phase 120 degree shift signals for the 3 phase driver…

      Please elaborate what kind of synchronization are you referring to?

    • how will the IRS 2330 IC will know the phases that are going to be delieverd by the PWM Controller circuit if they both deliver the same phase on the IGBT s then their might be single phasing right? Synchoronization between the signals that will trigger the IGBT s

    • the IC IRS 2330 is a specialized 3 phase driver device which will feed the phases exactly in the same sequence as supplied to its HIN, LIN pins, so there cannot be anything wrong in this regard.

      however the 3 phase generator must be accurate and must supply the 3 phase sequence with the correct required 120 degree phase shifts, that's the only critical thing that will need to be verified.

  38. i done this circuit by interfacing pic16f877a as pwm and frequency genrator with cd4035 circuit. But i am confused regarding to cd3045 circuit that the output frequency is just simple pwm base with shift of 120 degree but its not spwm. and when i interface your circuit with ir2110 base fet driver circuit it shows nothing in output.

    • the above circuit will produce a square wave 3 phase control, not an SPWM.

      for SPWM you may have to inject the PWM at the bases of the lower IGBTs

  39. Dear brother LEDs are blinking in 3 phase sequence if i give 1Hz at 4049, then what will be problem in driver ic 2113? Can i get ouput at no load condition?

    • Dear brother, it could mean that your full bridge driver IC is not responding.

      It will be difficult for me to troubleshoot without practically seeing it.

      pleas refer to the datasheet of the driver IC and see if you have done everything correctly as per the given specifications.

      • …if you connect your voltmeter across the "load" points you should be able to see the required AC without any load connected

  40. Brother i'm getting 6.76v from ic 4049 in every high and low logigate and i'm using ic 2113 for half bridge driver ic 3 sets in that i'm getting 80mv in ho and 25mv in lo, i didn't pass any dc at the drain side of the mosfet, if i passed 310v dc there will be no output in every phase, what will be the problem in that ? Pls help me out

    • measuring voltage is not the right method….you should measure frequency at the outputs of the 4049….

      you can make the frequency rate very low at the rate of 1 Hz and then check by connecting LEDs across the respective outputs of the 4049…if these LEDs blink in a 3 phase like sequence then you can be sure of the working….and then increase the frequency to 50Hz…

      after this you can feed the signal to the half bridge drivers for the final results….initially do not connect 310V….instead connect 12V and check the response using a lamp

  41. Hello Sir,
    I am a littlebit confused about connecting the 4049 in the 3phase generator. Vcc (+) goes to 1, -/GND to 8, but I don't understand the connection between 4035 Q1/2/3, 4049 & HIN/LIN 1/2/3 of the driver. Could you pls elaborate on it a little? Thx

    • Hello Julio,

      Q1,Q2, Q3 are associated with two more NOT gates from the IC CD4009. The 3 phase outputs from the 4035 circuit connects with the inputs of the 4049 circuit marked phase1, phase2, phase3…the outputs from the 4049 gate then integrates with the relevant pins HIN, LIN of the main driver IC.

      furthermore 4035 IC will need a 555 atable multivbrator circuit for acquiring clock signals at its pin#6

    • Yepp, I intend to make a multiplicator using a CD4046 PLL + SN74LS92 counter. It will make a reliable and fast 6x multiplication of the modulation frequency coming from IC1 555.
      Regarding the 4049, so let's say I connect 4035 Q1 to 4049 A (pin3) and LIN1 of the driver, and get HIN1 from 4049 G (pin2)? And similarly for the pins 5/4 and 6/7 for phase 2/3?

    • Hello Swagatam, ltns 🙂
      I was just wondering the other day – why do we need a multiplicator at all? Why dont we use IC1 & IC2 to generate 6x the desired frequency from the beginning? I mean if we need 50Hz x 3phase signal, lets generate 300Hz on IC1 and call it a day. Eventually in case of PWM frequency of 10kHz let's make it 60kHz on IC2. Let's say we don't want to go under 20Hz base modulation frequency, so we use the appropriate resistor in parallel to the control pot. Also for a standard 3ph motor we don't need more than let's say 100Hz, let's limit the pot size. So all in all, the applied modulation frequency would be between 120-600Hz with PWM of 60kHz (or even 120), directly on input of the 3 phase signal generator w/o the need of 6x multiplication. What am I overlooking? Some 555 limit?

    • Hello Julio, sorry I could not interpret your suggestion.

      where do you think the PWM could be applied directly?

      By multiplicator I believe you are referring to the mosfet driver IC stage, right? Please elaborate more on this.

    • OK, seems like I messed up a little. Let me explain.
      1. In your diagrams you use a pair of 555s as a PWM voltage controller to generate the PWM signal at the required modulation frequency (let's say modulation frequency fm = 50Hz with the pulse frequency fp = 10kHz).
      2. That PWM signal goes then to the frequency converter. You used a CD4060 with a coupled LED/LDR, I decided to use a CD4046 PLL + SN74LS92 counter (doesn’t matter, does the same). On the output you get your PWM signal with 6x fm (and also 6x fp for that matter).
      3. That multiplied PWM signal at 6fm and 6fp serves as a clock for the CD4035 Shift Register (3 phase signal generator stage), which divides the clock signal to 3 LIN/HIN pairs using CD4049.
      Now my question/idea is the following – how about to omit the frequency converter (point 2) altogether, generate the PWM (point 1) already at 6fm and 6fp to feed it to the shift register (point 3)?

    • I am still confused! you mean to say you want to eliminate the IC 555 stage?
      then how would you generate the PWMs corresponding to the varying 220V AC? These PWMs ultimate determine the RMS of the output voltage to the motor equivalent to the input mains AC

    • Nonono, I mean to eliminate the frequency converter stage. And generate the PWMs at 6x frequency from the beginning. As I said, you need a 3 phase 50Hz PWM signal on output. So you generate 6x50Hz = 300Hz from the 555s with the corresponding pulse frequency of 6x10kHz = 60kHz, and you have the same result as your original design after the frequency converter stage. Do I understand that correctly? Maybe I can't explain myself, or am I missing something?

    • please ignore the previous comment, may be I got it now.

      you want to eliminate the frequency converter stage which uses the 4060 IC or the one that you have referred to using 4046/74LS92, right?

      well this stage is employed to make the system automatic, so that the VFD becomes independent of manual adjustments, and is able to read the mains fluctuations and auto-adjust the V/F ratio for the motor.

    • Hmmm, now I'm confused. What mains fluctuations are you referring to? The input 1phase or 3 phase AC mains is rectified to DC both for the high voltage power stage and for low voltage 5 & 20V logic stage. The pulse frequency is constant and the pulse width only depends on the modulation frequency wave amplitude (at least after your soft start circuit saturates, thx for that one, too), which frequency depends on the settings of R1 (replaced with a pot) and C1.
      I feel like we are talking about the same think but somehow struggle to understand each other. Also it seems to me I am missing something terribly. Maybe I won't find out till I build the circuit finally at least on a breadboard. I wish I could skype you.

    • sorry…. actually it's not about the mains fluctuation issue, the frequency converter stage is for making the unit automatically compatible with all the the viable voltage input ranges, such as 440V, 120V, 220V, etc so that it becomes universally acceptable for all, and no manual settings are required by the user who buys the unit.
      sorry I do not have a skype account, but now it seems we have almost sorted it out finally

    • ….the frequency may be constant from IC1 of the first circuit, but the PWM from IC2 is dependent on the 12V supply, which is in turn proportionately dependent on the mains input voltage level….so this PWM needs to be converted into a proportionately adjusting frequency for the driver stage and eventually for the motor….otherwise if the frequency is not changed, then the V/F ratio would become incorrect for the particular motor and the whole purpose of the circuit would become zero.

  42. Good day Sir,
    Can you please post another circuit for a single phase brushed/brushless A/C motor. Thanks in advance.

  43. please explain how the voltage is changing in this ckts. and explain that with low frequency low voltage and high frequency high voltage is provide the ckt m i right?

  44. Sir, if this circuit is used for a submersible motor of 10 HP, 415V with long cable of 1000 feet , it need any choke in its output?

    then , what will be the swg and turns of the choke.

    • Hi SS, presently I do not have its calculation details, I'll try to investigate and possibly update it for you in the above post.

    • Hi sir,I have refer other vfd circuits also. they said,"if the frequency of the pwm is b/w 3.5khz to15khz only, the motor will be run with less hormonics. Otherwise it will damage the bearings".

      In your circuit, what will be the frequency of the pwm from 555 IC?

    • Hello Sivaraj, you can use any wattage motor as per your specifications just by upgrading the IGBTs appropriately

  45. Hello sir,
    Generally, In other VDF circuits comparator is used to generate the pwm which is corresponds to given signal i.e, sine wave or square wave.In your circuit ,How did you give a separate pwm signal that is not corresponds to the input. If this pwm is not given to it what happens

    • Hello S.Sageyu, a synchronized PWM is good but it's not absolutely necessary, in the above circuit the PWMs are adjusted so that the output's RMS matches with the AC mains voltage RMS. This reduces harmonics and creates safe voltage parameters for the motor. if the PWM is not introduced then the output will be a square wave with a lot of harmonics and generate noise while the motor is running.

    • Sir, I have decided to use FGA25N120D IGBT.Is this IGBT can be used for up to what hp motor?can i use the IR 2130 instead for IRS 2330 in your circuit.

    • this IGBT may be capable of handling upto 50Hp motors if the voltage is 1kv, otherwise upto 10hp at 220V

      yes the two ICs can be replaced with each other

    • Hello sir fine?i have almost finish the above circuit using the igbt Fga 25n120d.i have littlebit confused that if the additional soft recovery diode is need for this IGBT or not in case of inductive load

    • Sir,can I use the fast rectifier diode instead for soft recovery diode since it is not available in the shop.
      In case it is not possible tell me the alternate solution

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