In this post I have explained a single phase variable frequency drive circuit or a VFD circuit for controlling AC motor sped without affecting their operational specifications.
What is a VFD
Motors and other similar inductive loads specifically do not "like" operating with frequencies that might be not within their manufacturing specs, and tend to become a lot inefficient if forced to under such abnormal conditions.
For example a motor specified for operating with 60Hz may not be recommended to work with frequencies of 50 Hz or other ranges.
Doing so can produce undesirable results such as heating up of the motor, lower or higher than the required speeds and abnormally high consumption making things very inefficient and lower life degradation of the connected device.
However operating motors under different input frequency conditions often becomes a compulsion and under such situations a VFD or a variable frequency Drive circuit can become very handy.
A VFD is a device which allows the user to control the speed of an AC motor by adjusting the frequency and voltage of the input supply as per the motor specifications.
This also means that a VFD allows us to operate any AC motor through any available grid AC supply regardless of its voltage and frequency specs, by suitably customizing the VFD frequency and voltage as per the motor specifications.
This is normally done using the given control in the form of a variable knob scaled with different frequency calibration.
Making a VFD at home may sound to be a difficult proposition, however a look at the design suggested below shows that after all it's not so difficult to build this very useful device (designed by me).
How it Works
If you do not wish to read the whole explanation, then you can watch this video instead:
OK, so I have designed this simple, basic VFD controller circuit which can be used to control all types of 220V or 120V single phase AC motor, as per the desired specifications. Let's try to understand how the circuit is designed to work.
Referring to the above circuit diagram the proposed VFD circuit works in this way: The IC IRS2453 is configured as the basic full bridge or H-bridge inverter circuit which generates square wave output whose frequency is determined by the values of the Rt and Ct components of the circuit.
The output of this inverter is used to control the desired motor, whose speed need to be controlled as per the VFD rules.
In order to convert this square wave inverter into a sine wave VFD circuit, I have configured an adjustable SPWM generator stage using the IC 555 astable and an op-amp comparator.
The IC 555 is wired as a PWM astable circuit to generate the fast triangle waves as the carrier frequency which is fed to the non-inverting input of the comparator op-amp IC 741.
The slow triangle wave, which acts as the reference signal, is extracted from the Rt, Ct junction of the IRS2453 IC and is fed to the inverting pin #2 of the comparator IC 741.
The reference signal is intentionally derived from the Rt, Ct pin of the inverter IC to ensure that the SPWMs are perfectly synchronized with the set frequency of the inverter.
This frequency caan be set by adjusting the Rt resistor which can be a potentiometer.
The 741 IC compares the two input waveforms and generates an equuivaalent SPWM output waveform from its pin#6.
This output is integrated with the low side MOSFET gates of the H-bridge inverter IC so that the square wave operation of the inverter is transformed into an SPWM equivalent sine wave output.
Now, how does this basic sine wave inverter circuit turns into a variable frequency drive?
It is done by providing the adjustments for the frequency control and the RMS voltage control of the inverter output which controls the motor.
So with this sine wave inverter you can adjust the output RMS frequency by adjusting the duty cycle of the SPWM carrier wave and the frequency can be adjusted by adjusting the Rt resistor of the inverter IC which supplies the reference frequency for the SPWM.
How to Calculate Single Phase VFD Parameters
Input Power Calculations:
Power Factor (PF):
This is all about measuring how efficiently we are using AC power. It is extremely important for making sure we size the Variable Frequency Drive (VFD) correctly.
Apparent Power (S):
This represents the total power that’s supplied to the VFD, and it includes both real power and reactive power.
Formula: S = V * I
Real Power (P):
This is the actual power that the motor uses to do its work.
Formula: P = V * I * PF
Reactive Power (Q):
This is the power that bounces back and forth between the source and the load without doing any useful work.
Formula: Q = √(S² - P²)
Output Power Calculations:
Motor Power (Pmotor):
This refers to the mechanical power that comes out of the motor.
Formula: Pmotor = (Torque * Speed) / 9550 (for horsepower).
The constant 9550 is an important number we use in the formula that connects power, torque, and rotational speed when we’re working with the SI system of units.
Formula:
Power (kW) = Torque (Nm) * Speed (rpm) / 9550
What is its Importance
So, what is so important with the constant 9550? It comes from how we convert between different units of power (in kilowatts), torque (in Newton-meters), and rotational speed (in revolutions per minute). This number helps us to tackle the differences in these units, making sure that our equation works correctly.
- Power is measured in watts (W) or kilowatts (kW).
- Torque is measured in Newton-meters (Nm).
- Rotational speed is measured in revolutions per minute (rpm).
To get to that constant 9550, we need to think about a few things:
- Converting power from kW to W.
- Changing rotational speed from rpm to radians per second.
- Using the relationship that says power equals torque times angular velocity (power = torque * angular velocity).
When we do these conversions and simplify everything, we end up with that handy constant 9550 in our formula.
Remember:
This formula is specifically designed for the SI unit system. If you happen to be using different units, for example like horsepower or foot-pounds, then you will need to use a different conversion factor to make it work.
Motor Efficiency (η):
This is a measure of how well the motor converts input power into output power.
Formula: η = Pmotor / Pinput
VFD Sizing:
VFD Power Rating:
The power rating of the VFD needs to be higher than the apparent power of the motor's, so that it can handle any potential overloads without an issue.
Input Current:
We can calculate the input current based on the VFD's power rating and the input voltage specifications.
Output Current:
We also need to figure out the output current based on the power rating of the motor and output voltage.
Motor Speed Control:
Motor Speed (N):
The speed of an induction motor is directly connected to the frequency of the voltage we apply.
Formula: N = (120 * f) / P (where f is frequency and P is the number of poles)
Have Questions? Please Leave a Comment. I have answered over 50,000. Kindly ensure the comments are related to the above topic.
Hello Sir, how do I control the full H-bridge( with 2110) using Arduino in terms of code and connection?
Hello Everisto, you can use the following Arduino code and integrate it with your 2110 IC for implementing an H-bridge inverter:
https://www.homemade-circuits.com/simple-arduino-sine-wave-inverter/
I wish you did a demonstration of a single-phase project in Multisim using P type and N type Mosfets
Want complete guidence 3 phase vfd circuit diagram pcb ? Parts from where to buy
3 phase VFD circuit is recommended only for the experts, it may not be suitable for newcomers.
how are VFD’s applied to BLDC motors and what are the limits of “overspeed” based on frequency limits?
Thanks
Doug
Hi, Can this very useful circuit be used to drive a syncronous 220-240VAC motor?
I think it can be used to drive the specified motor.
Hi, I have couple of questions…
I would like to control a 1/2 HP single phase pump. The pump uses a permanent capacitor. Could I use a two phase VFD drive eliminating the need for the capacitor?
I would need to know the phase shift that the capacitor introduces.
I would also like to use a solar panel to drive the pump, varying the speed (freq.) and hence power according radiation…. the panel outputs 9.85 Amps @ 45.2 Volts (@ max radiation). I guess I would need a step up transformer to bring the voltage up to 220 V.
Hi, Sorry, I am not an expert with motors, so I am not sure whether a capacitor start motor can be controlled with a 2 phase VFD or not, or whether the capacitor can be removed or not.
If you want to use a solar panel, then certainly you will need to use an inverter to convert the solar panel DC into a 220 AC for the motor
hello, the circuits are tested? I did a simulation of the last schematic and it doesn’t work, included with the optocouplers to drive the mosfets
Hello, you must do the simulation in a step wise manner, first try simulating the 555 section, then the 4017 section.
The 555 and the 4017 sections are perfectly tested OK, but the mosfet section has problems, which might need some corrections. I have added the necessary warning message with the diagram.
can updated circuit with irs2453 be directly used for 250-300 v. or it need to modify as stated in comments using 4N25 optocoupler
If you are using IRS2453 IC with 4 N channel mosfets then you can easily use 300 v directly with the mosfets, no optocouplers will be required.
Hi Swagatam,
thank you very much for this interesting article!
I’d like to build a VFD for a 240V universal motor of about 1 kW; it might peak at 40A during startup and at low speeds/high loads and I was not able to find suitable mosfets, since I’m also concerned that back emf can reach more than 600V.
Do you have any suggestion for suitable mosfets P/N (or mosfets configuration), and do you believe I should use some snubber network or the like?
I’d like very much to hear any suggestion from you, thanks!
Thank you LCU,
For the P channel you can try FQP4P40 mosfets and IRF740 for the N channel. However, there seems to be a mistake in the last diagram.
The source voltage for the P channel mosfets is 310V, and the gate voltage is 12V which cannot work. For switching OFF the P channel effectively, its gate voltage must be same as its source voltage.
Therefore we may have to modify the H bridge section in the last diagram through opto couplers for effective switching of the P channel mosfet as shown in the following example design:
FQP4P40 has a max Vgs of 30V or -30V. When the optocoupler shorts the gate to ground you will have around 0V at the gate and 310V at the source. Would this not make Vgs -310V and destroy the mosfet?
You are right! I think this can be rectified by adding a 15V zener diode across the gate/source pins of the P channel mosfets.
whats the function of bc 557 in the last circuit ? can it or anything else be removed to simplify even more it ?
BC557 allows the IC2 555 to work with a constant current which ensures the PWMs are always consistent regardless of Dc supply variations
Dear Sir,
I wish to make your last drawing…..using 8 mosfet…it is simple from other…So pl give mosfets number…8 nos..
Hello Anilkumar, the upper mosfets can be any 400 V P-channel mosfets, and the low side mosfets can be any 400 V mosfets.
Sir,
I wants single phase 230v 50 hz 2800rpm circuit…is it possible for 2800rpm pump…
Yes that’s possible by adjusting the output frequency to 50 Hz.
Sir,
I will try this method Surely…..
Sure Anil, you can try it.
in the last circuit you changed again to the 4017 ic or is it worng ?
Nothing wrong, it is correct.
is it 10-500hz in 50hz line right ? in 60hz will be 12-600hz ? can’t it go lower like 3-6hz ? what modification it would need for that ?
Frequency can be adjusted by adjusting the R1 pot in the last circuit. It can be any value between 10 and 500 Hz.
and can it be lower than 10 ?
yes it can be lower than 10 Hz
can i reduce this pot to have less range like using 50k or 10k pot wil give what range ?
what pot can give 0-100hz ?
You can try a 100k pot
Hello swagatam
my fridge is 200watts . But because of high surge / starting current the inverter trips. What is the best solution to run the fridge? super capacitor , car battery , change to invreter compressor etc?
Hello JK, The only feasible way is to either to adjust the trip setting to higher level, r to replace the inverter with a higher power inverter. If existing inverter power can be upgraded by adding more number of external batteries then that is also a good option. Super capacitors might not be capable of handling this issue unless many of them are used.
hi sir, i have a problem similar to this project would you help me to answer my question? i want to make a vfd by using igbt instead of mosfet. in all full bridge circuits with mosfets we have both n & p channel mosfets but on internet there are only n-channel igbt s. for making a full bridge with igbt should i use only four n-channel igbt ? ( do igbts have p-channel or they are only in n-channel?).many thanks
Shapur, it depends on the driver IC. If the driver IC is built for driving only n channel deice then p channel cannot be used, and vice versa.
Hello Swagatam,
is this circuit able to run a single phase induction motor capacitor start-capacitor run type?
If not, is there a possibility to make this kind of speed control for this motor type?
Regards.
Hello Bursac, yes according to me the output can be used for operating a capacitor-start type motor, provided the output AC is filtered with some large non-polar capacitors.
I”m a student of University college
I have a project in a single phase variable frequency driver
what is the most accurate circuit diagram here .
The last circuit is the easiest one, but it will need to be built and verified stage-wise and is recommended only for experts who are well versed with electronic circuits, and exactly know how to proceed with the steps, with the help of an oscilloscope.
Also, please note that the various stages involved in the diagram are tested individually for other applications, but the whole unit as one has not been tested yet by me.
Your circuit are very interesting.
I would like to vary the speed of 1.5 HP induction motor.
Is it possible to have a complete circuit diagram including all the components value.
Thank you, I have updated the parts in the last diagram clearly. All the resistors are 1/4 watt, and all the non-polar capacitors are ceramic type.
MOSFETs will be as per the input voltage rating
Hello Sir,
Is this possible to start single phase induction motor without start capacitor using above circuit?
Regards
Manoj
Hello Manoj, I don’t think that’s possible with any circuit
i need full circuit diagram of Single Phase Variable Frequency Drive VFD Circuit
thanks
I am Dip. Elec. Engr.
I want to run variable frequency device for my sewing machine.
I want to use IGBT
which circuit I should use?
You can use the last circuit!
Hii sir..
Can I use this circuit for 1.5hp single phase motor…which is required to run in 10rpm..
For long duration..
And plz explain me how inverter circuit is formed in the above circuit
Thanks sir…im waiting for Ur reply
Hi Chetan, yes you can try it, but make sure you do it only once you have perfectly understood the working of all the stages of the circuit.
Please read the circuit operation for all the details.
Dear Sirs,
I have to control a pump driven by an induction asincron motor, single phase 220V AC, 200w. The motor is sealed and the only „connection” to it is the 3-wire cable: line, null and earth.
The VFD has to run between 20 Hz (say LF) and 50Hz (say HF). The time to increase from LF to HF is variable depending the application (up to minutes). Also the value of LF may be variable. The VFD control (time to increase the frequency)will be made by an Arduino Nano.
Another aspect is the size of VFD. The room is restricted and may depend on application, basically, the body has to be slim and long. So I have to design my own PCB to cope with the room available in each project.
Which might be the circumstances to have a wiring diagram for a VFD 220V single phase input-output, 200w (1/4 HP)?
Thank you.
Hello sir,
I have a my sweety vfd running my CNC Router spindle and it ran fine for months then all of the sudden errored out with a drive circuit error. I can get it to power up and run but the spindle longer turns on. Any ideas?
Hello Jason, most probably it could be due to damaged MOSFETs which are directly responsible for controlling the motor…
Hellow
I am curious and it did not say in the article that I saw. Is it 110 in and what out? Or is it 220 in? If it is 220 can it be altered? I hope so I live in a trailer park and 220 is forbidden by management. But I have a big 110 breaker just setting their unused waiting for me to run it to the shed/machine shop So I can fire up my old professional machines with the help of your VFD I hope. I have had a great deal of practice making my own circuit boards this one seems a lot bigger then what I am used to but I will not be a problem. I have a nice little CNC board etcher that I made sitting in my bedroom.
Hi, the concept can be used with 220V and 110V as well. However the design is indeed complex, especially for anybody who hasn’t built a full bridge inverter yet. I would rather recommend building the second circuit from the following link, and test it on a motor. If you succeed then you can alter the input side and replace it with the VFD control from the above article:
https://www.homemade-circuits.com/5kva-transformerless-inverter-circuit/
hello sir , i want make single phase vfd for a fan(i e. 230 v 5 A, 60-90 W) . I want generate PWM signals by ARDINO. So can you suggest me the simulation ckt & the hardware circuit . Please send me the information regarding that.
Hi Shiva, you can try this:
https://www.homemade-circuits.com/arduino-pwm-signal-generator/
Hello Sir .
How are you ?
Your VFD circuit is correct ?
It is because sometimes on internet some person adds incorrect circuits . Kindly give me a true Answer … I am very thanksfull to you .
Thank you Muhammad,
the concept is correct, but please build it only if you have understood everything correctly and have the required level of expertise, otherwise you may not succeed with this complex project.
Hi Swagatam ,
can you give me a simulation for the scheme,
I’ve tried proteus, but I can’t find ir2110 on my proteus. please help me sir
I have a project to control a single phase motor (VFD)
Please help … rakirebels@gmail.com
Thanks & regard
Sorry Raki, I can’t because normally I don’t depend on software simulation results, instead I believe in mind simulation and practical testing.
Thanks ..
I want to use your scheme for controlling a single phase motor.
1500 watt single phase motor
I have to use half bridge or full bridge ?
thanks & regard
You will need a full bridge circuit, a half bridge is mistakenly shown…..it is not recommended for any motor.
saya membaca artikel anda tentang ” Arduino SPWM Generator Circuit – Code Details and Diagram ” (// By Swagatam (my first Arduino Code)
bisakah code itu dimodifikasi ? saya membutuhkan pengendalian frekuensi untuk mengatur kecepatan motor satu fasa. saya menggunakan IC ir2110 sebagai driver
Thanks & regard
Yes it can be modified but it cannot be varied using a pot.
The total time of the two sets of codes is 20 ms, so each set is 10 ms long…you can adjust the microsecond values to increase or decrease the 10 ms value to any other desired value proportionately.
hello Mr. Swag,
I assembled a half-wave inverter. I experienced failure. i want to ask, what is the output voltage on pin 2 and 7 ic 4017? , what is the output voltage on the pin HO, LO,VB and VS ic ir2100. at no load condition .. thanks Mr.Swag
Hello Raki, you must build and verify the different stages separately, and then integrate them together. The voltages will not reveal anything because the outputs are sequencing at a high frequency. You will need a frequency meter and an oscilloscope to test the various points, and before that you will have to understand how all the stages and the ICs are designed to work, their specifications etc.
This project is not for the newcomers.
hello sir .
may i know your email
thanks & regard
Hello Raki,
please see the “contact” link at the top of the page.
hello sir,
in a half-wave circuit
Is the negative voltage on the motor connected only to the motor?
or also connected to ground (pin # source on LO mosfet)
best regards
Hello Raki,
All the ground symbols are common and should be connected with the each other.
Hello Sir …
in my halfbridge circuit
lf pin3 ic2 is not connected to the gate, the voltage at the source is measured 180V, and the lamp is on
but if pin3 ic2 is connected to the gate, the voltage at the source is measured 4V, and the lamp is off.
if all components are installed according to your design and soldered correctly. what else should i do?
please give me your advice
thank & regard
Hello Raki, If you assemble everything together then it may show many problems. So you will have to build and confirm the various stages separately, and then join them step by step.
First build the IC1 and IC 2 stages and check the pin 3 of IC2 for a varying PWM in response to a varying external voltage at pin 5 of IC2.
After this build IC 4017 stage and connect IC1 output with it and confirm the output of IC 4017.
After this build the half bridge, and connect it with IC 4017 and check how a load responds to this.
If everything work perfectly then finally connect the pin3 of IC2 wit the MOSFeTs.
Swag,
I would like to use your design for a lathe in my wood shop. My question is will this work for my application?
The motor is 3/4 hp, 115V, 1PH, 60 Hz, 1720 RPM (no load), 6.7 FLA.
Please let me know. Thank you.
Hi Paul, it will surely work for the specified motor. I would recommend the last circuit since it’s a full bridge circuit and will provide full control of the motor speed.
Thank you very much! I am anxious to give this a try and I’m sure I will be asking a few more questions before I am all done.
Thank you, wish you all the best!
What is the purpose of decade counter 4017 in this circuit?
It is for driving the IR2110 IC inputs
Hello Swagatam,
Very nice post. I was wondering if I can use this circuit to control the speed of an single phase capacitor run induction motor. For example one like those small fan motor of the evaporating unit of an Air conditioning
Many thanks
Thank you Steve, yes it can be definitely used. But I am wondering why can’t an ordinary light dimmer switch be used for the same purpose?
Hi Mr Swag i redesigned my H bridge driver and if i test it with motor ,my ic driver just brew up and the only pin that may course this problem is pin 5 since it connected to high voltage and there is no diode or resistor across it ,is it correct like this? im scared to put another one if it blow again i will be in short of them
Hi Ayanda, As you will understand that the H-bridge design is a standard design taken from the datasheet of the IC, so it has to be correct in every manner, pin#5 of the IR2110 is correctly configured, since it is as per the diagram in the datasheet.
Configuring an H-bridge using driver IC is always a little problematic unless it si done on a well designed PCB, and make sure to add 1k resistors across gate/drain of each mosfets, this might help to safeguard, but you can be never sure unless you have the most correctly designed PCB layout for the H-bridge.
If you want to avoid a driver IC, you can probably opt for the following H-bridge concept:
https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/
you can connect the NAND inputs to the IC 4017 outputs
thanks bro i will do that ,maybe there is a little infomation that i have missed but protecting it would help me
Wish you all the best bro!
Dear MR Swag,
i want to make this circuit of VFD but using arduino as the designed one in https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/
but i need to vary the frequency using the arduino itself.will be any need for the 555 timers and ic 4017 ?? and will be the arduino Uno effective in changing the frequency ?
Mohammad,
It may be possible to replace IC1, IC2 and the 4017 with an Arduino, but designing the program can be complex. However if you only want the frequency adjustment to be implemented from the Arduino, in that case you can replace IC section with any Arduino frequency generator stage
Thanks for the reply mr swag,
what i really need is to control motor speed using arduino and the power source for the circuit is from AC 220 volt which is available in any home not a DC batteries as implemented in https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/
Mohammad, for this you will have to have an adjustable PWM output from the same Arduino board, this pwm could be configured with the low side mosfet gates for implementing the required motor control action
thanks Mr Swag for your reply,
thank god , i found a code for varying the frequency using arduino but now i want to change speed for 240 v AC induction motor and the output of the arduino is 5 volt.
will the use of nand concept of ic4093 useful with arduino which now vary the frequency or not ?? and how can i reach to 240 v of the ac motor Will the transformer concept 12-240 will be useful and will be the output frequency from the transformer variable or fixed ??
Muhammad, please specify the pinouts and the configuration of your pwm control output. I may try to solve it
I just now remembered that the pwm control can be implemented through an arrangement that may allow the SPWM width control for this design:
https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/
Dear Mr Swag,
thank you so much for your support;
i just need two pins from arduino as 9 and 10 for pwm as you mentioned in
https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/
so that the arduino can change the frequency from 0 to 50 to control motor speed.
the AC induction motor specification 250W 1.5A 240 V. by varying the output frequency of the motor from 0 to 50 hz the speed of the motor will change but i do not want to use a battery as a power source for the circuit i just need to get its power from home ac electricity(220 V).the speed control of the motor will be by arduino. will the nand concept mentioned in
https://www.homemade-circuits.com/arduino-full-bridge-h-bridge-sinewave-inverter-circuit/ be helpful for my case?
Mohammad, I was asking about your Arduino circuit which you found from another source. I wanted to know about it, since you said you found the PWM control codes.
OK, I understood, you are referring to my recommendation, regarding varying of 8 and 9 pin PWM widths…let me think about it.
Dear Mr Swag
the source for varying the frequency in single phase motor
https://github.com/Terbytes/Arduino-Atmel-sPWM
https://www.youtube.com/watch?v=3DjKxDL_Qc0&t=925s
OK, but this will need to be included in the Arduino system which is explained in the full bridge Arduino article??
ok mr swag but my question is will be the output frequency of transformer fixed or variable and i read that the current will step down in the case of using transformer and i don’t want to use a battery how can i achieve this using AC as the power source for the circuit ??
frequency would be fixed because we won’t be using V/Hz principle, we would be using a PWM control based principle. You can use AC by feeding rectified DC 220V to the mosfet supply lines.
Thanks sir for your response.but if i connect pin 3 of ic1 automatically to ct of IRS what will be the benfit of ic2 ?? and i could not find IRS2453 in my city are there other replacements ?? and what about the previous circuit which uses IR2110 is it synchronized with the SPWM from the IC 555 or has the same issue ?
Hi Mohammad, IC2 is for generating the SPWM, IC1 is for generating sample triangle waves for IC2, all are interdependent with each other.
You can Google “full bridge driver IC”, or half bridge driver IC, and see which one is available in your area.
The previous one is synchronized through IC 4017.
hi sir,
if i have AC 220 V 1/4 hp compressor of household refrigerator and i want control its speed what is configuration suitable for Rt/Ct associated with the IRS2453 and R1 associated with IC1 ??
Hi Muhammad, the full bridge stage is actually not synchronized with the SPWM from the IC 555, therefore the output may not be correctly optimized AC. Therefore I would suggest to eliminate Rt/Ct, and feed the Ct pin of the IC with frequency from pin#3 of IC1.
IC1 frequency may be set at the desired output frequency by measuring the output of IRS IC with a frequency meter and simultaneously setting the R1 220K preset…this will allow the full bridge stage to be synchronized with the SPWM control frequency and also allow to get the required 50Hz frequency at the output
Thanks bro,one more question ,why is it necessary for Drain pin in HO side is connected to power while the other one is connected to load. will this not affect the mosfet ?,just asking i did read about the mosfet from the page you shared yesterday.
Ayanda, actually you have asked a very important, I am sorry I think the half bridge configuration which was taken from the datasheet itself is not correctly connected. The connection should be in the following manner, I’ll correct all the diagrams soon
Thank you very much Swag we appreciate your help bro.i have learnt a lot now and i’m hoping to get this done before the second of may which is two weeks from now and i will be presenting my project but i’m still working on it.
You are most welcome Ayanda, I have done the necessary correction in the design, you may check it out now.
Hey swag .
Plzz give me a motor rating …??my project is 1 phase vfd for 0.5hp induction motor can I used your circuit in my project ..??? Plzz help me broo
Hi Satyajeet, the motor rating will depend on the mosfet rating and the applied voltage to the drains of the mosfets, or vice versa, meaning the mosfet and the supply voltage could be selected as per the motor specifications.
Hi Mr. swagatam.
can u help me with single phase VFD run with arduino . MATLAB/SIMULINK code has been done to drive the bipolar full bridge PWM signal to MOSFET with variable frequency and modulation and will upload to the arduino.
So, my problem is how to make circuit for gate drive the MOSFET to drive the 240V 70W ceiling fan.? can u give me any suggestion. Thanks..
Hi ISZ, An exactly similar question was asked many days ago by one of the readers and I had provided him and appropriate diagram for implementing the same, now it may be very difficult for me to search that particular comment.
Anyway if you are trying to feed the bipolar pulses into a n-channel based full bridge mosfet configuration then you might require a bootstrapping mechanism for the high side mosfets, right? Without this you won’t be able to drive the high side mosfets, so have you taken care of this??
hello sir ,i made a simulation for this circuit in multisim program but it doesn’t work for me.i can send you a photo from the simulated circuit if you wish sir :).
Hello Mohammad, Simulators can produce wrong and misleading results, how can you confirm it is giving you the right results? If you build this circuit step wise with proper understanding the circuit will surely work…
Ok,thank you so much sir.I will do my best with god permission.
Hello Mr. Swagatam, could you explain why the output (pin3) of the second 555 is connected to the HO and HI outputs with inversely polarized diodes? regards
Hello Mr. Benjamin, that is not correct, and I have mentioned about this and have presented the finalized design at the end of the post….the diode links must be connected with the mosfet gates.
Hello Mr. Swagatam, would you be so kind as to send me the image of the last scheme that has the corrections to my email? Since when downloading the image you can not see the values of the components well. Greetings Benjamin
Hello Benjamin, I’ll try to update the diagram in the article soon with larger component numbers.
Okay,thank you.
Thanks man
Welcome dear!!
Hello again .
With all due respect brother I have one more question .
1. Why 2nd 555’s I mean ic2 output is directly going to mosfet’s gate ?
Please clearify this what’s purpose of it . If we remove ic2 from circuit it’s still working .
Hi, If you are not including R8 pot and not integrating the IC2 output with the mosfet gates, then you won’t be able to control the speed of the motor, the option will be simply lost.
IC2 helps to transform or chop the mosfet gate drive into an SPWM format, and R8 allows the PWM control of this SPWM, meaning by rotating R8 you can reduce or increase the SPWM duty cycle or the width of the pulses. narrow width will cause decrease in motor speed, wider pulses will allow higher speeds.
hello sir,
we have completed this project and i have a few questions please answer these questions it will be a great help 1.why we are using 2 555 ic’s ?
2. why we using pin 2 and 7 of 4017 ?
3. we have used ct also for protection i will share the pictures .
Hello Farhan,
The two IC 555 are used for creating SPWMs in response to the 100Hz sinewave ripple sample achieved from the bridge at pin#5 of IC2
The actual sequencing of IC 4017 is from pin#3 > 2 > 4 > 7…by skipping pin#3 and pin#4, we are trying to insert a good “dead time” for the mosfets, although this can also result in significant amount of voltage drop at the output.
Also, the use of a half bridge at the output could result in further drop in voltage.
so the above things must be considered….
the half-bridge could be replaced with a full-bridge driver circuit for ensuring the correct level of output for the motor.
sure, the images will be greatly welcomed here,,,keep up the good work.
We have hooked up the vfd in stages and began testing with and oscilloscope. We are getting a square wave coming out of pin three of ic2 and 1c1. We also looked through the previous comments and removed the 557 and other components as you stated. What should we be looking for on the oscilloscope going to the 4017 and further more on the ir2110?
isolate the IC1/IC2 entirely and test it separately, connect the upper arm of the R8 pot at pin#5 of IC2 with the positive line.
varying this pot should create a variable PWM at pin#3 of IC2. The frequency of this PWM can be varied by adjusting R1.
Once this is confirmed, connect the R8 upper arm with 100Hz from the bridge, and check whether pin#3 of the IC 2 is producing an SPWM or not, it should.
Once this is confirmed you can integrate the IC4017 with this stage and verify the alternating pulses across pin#2 and pin#7.
similarly confirm the motor half bridge driver separately and finally integrate it with the IC 4017 output
I have hooked up the whole circuit and i am able to vary my current. The problem is i am feeding the top mosfet with 170 v dc to run a 120vac motor but I’m only seeing about 4vac across where the motor would go. Any thoughts on the possible issue?
Hooking up the whole circuit is not the right way to go, you must build it stages-wise and confirm the stages separately, once confirmed then you can integrate them together for the finals results….as you can see there are many stages in the design, unless you are sure each one of them are doing their job correctly you cannot be sure of the output performance.
please check the mosfet gates with an oscilloscope, check what waveform you get here? If it’s an SPWM then it is fine otherwise you may have to go right back and begin investigating from the IC1, Ic2 stages.
Okay, to Know, in what frecuency ranges can you works
you can set the frequency by adjusting R1 to the correct range, this can be set using a frequency meter.
Thanks for answering Mr. Swagatam. Excuse me I thought the circuit was for that purpose (vary the speed). But could I use it for that purpose or not?
Benjamin, you should only use the voltage control pot for varying speed, not the frequency pot
Hello Mr. Swagatam, first I wanted to thank you for all your contributions to fans like me.
I have a doubt about the circuit, by reducing the frequency of the motor this consumes more current, how do you solve that problem. As far as I know, the voltage applied to the motor must be reduced, but I do not see that system in the circuit. Greetings Ben.
Thank you Benjamin,
The frequency adjustment here is not for controlling speed, it is for ensuring that the motor operates with the correct frequency as specified by its manufacturer. It is specifically used when a 60Hz motor is being used with a 50 Hz source and vice versa, and then the pot may be used for correcting the frequency as per the spces.
the voltage output can be varied by adjusting the pot at pin#5 of IC2
Good morning sir. Pls, after putting up the circuit, I realised that there was no signal entering into pot 14 of IC4017. Sir, pls, wat do u think could be the problem? Thanks in anticipation as I await your response.
Good morning stephen,
if you put up the whole circuit together, it is never going to work for sure, and that’s true for most of the circuits which have different stages.
you should build and confirm them stagewise, and this will require some serious understanding regarding the various stages.
anyway, by pot 14 you mean to say pin#14?
from where is pin#14 getting its signal? it is from pin#3 of IC1 right?, so check whether your IC1 is oscillating or not…keep verifying all the stages in the same manner.
by the way the following parts can be removed from the last diagram
T2, R9, R10, C7, C6, and connect pin#16 of IC 4017 directly to the positive line
I have done what u told me to do but what I realized is that it is only the pin Ho dat has voltage on it while the pin Lo does not and variation of the two potentiometer does not have effect on the Ho and Lo voltage. Sir, what else do u think I can do.
did you check whether IC1 was generating the oscillations or not…. in response to these osculations at pin#14 of the IC4017 it is supposed to generate alternating ON/OFF voltage across its pin2 and pin#7, isolate the respective stages and first confirm them separately….checking HIN and LIN can be done later on…
IC2 pin#3 should be generating varying PWM in response to a varying voltage at its pin#5, this is the next possible thing that you must confirm
Thank u sir, will give it a trial and get back to you.
you are welcome?
when the R8 potentiometer is adjusted, what is the variable parameter here? its variable the voltage or variable the ripple frequency 100Hz to pin 5?
the variable parameter is the voltage of the ripple input, or the amplitude of the applied ripples…