So this is actually an induction motor? You are wanting to make your own V/f drive? That's
rather crucial information.
You must vary the voltage as well as the frequency for a 3-phase induction motor or it'll burn out
at low frequency, since the current is limited by the large winding inductance.
Maryem:
i want control the speed of motor(230V-50hz) by varing the frequency
This doesn't make sense, as in a contradiction between '50 Hz' and 'varying frequency'.
Southpark:
This doesn't make sense, as in a contradiction between '50 Hz' and 'varying frequency'.
i hope varing the speed of the motor by varing the frequency or the duty cycle of the PWM signals
I'll repeat my question:
So this is actually an induction motor? You are wanting to make your own V/f drive? That's
rather crucial information.
its an induction motor withmy own V/F drive
So you will need to vary the amplitude alongside the frequency, otherwise the motor will overheat at
low frequency - the inductance dominates so that the current is inversely proportional to the frequency
at a fixed voltage drive.
So the first thing is to add amplitude scaling into the PWM generation, which your code doesn't have AFAICT.
It shoud work Your problem is that this code is a 3 phase Inverter algorithm. So you are generating PWM Peek's.. U need to modify the PWM signal to sinus wave's and then with a logical unit Split the upper(High) and under(Low) site. So U gona get a High and a Low site.. so 1 wire with PMW Peeks to a modified sinus wave an split to High and Low site / channel.. where the 3 chanel will give U the 3 High and 3 Low site..
But to manage it, still needs a a little Elektronical/ radio elektonik skill to make this happen!! Retrifier diod will not fo the trick.. its a PWM signal.. from 0v to pick Hillvolt no under site..- current..
After spliting, the 6 channel can be feed to a (half-full-6-7) Mosfet drive/ IGBT or IGCT..
Have funn!
by varing the frequency or the duty cycle of the PWM signals
PWM stands for Pulse Width Modulation
The Pulse Width is varied.
Frequency is a term used with signals that have a constant pulse width.
The frequency may change but the pulse width does not.
Using the term "frequency" in the same sentence with "pulse width" makes no sense.
Either you vary the frequency (and keep the pulse width constant)
or you vary the pulse width, which does not change the frequency because the time from leading edge
to leading edge remains the same. (what changes is the DUTY CYCLE (ON TIME to OFF TIME ratio)
If you are using 230vac/50 Hz, the FREQUENCY is 50 Hz.
You can VARY the PULSE WIDTH, but the FREQUENCY is still 50 Hz.
Obviously, PWM and 230vac SINEWAVE are mutually EXCLUSIVE.
If you are trying to SYNTHESIZE 230vac SINEWAVE using PWM on the IGBT gates then you should say so.
Can you post a SCHEMATIC of your SYSTEM ?
IF on the other hand , you want to create a VARIABLE FREQUENCY DRIVE, (VFD), this is a completely
different animal.
You've replied to a 2-year old comment I'm afraid...
That's how long it took me to think of an answer
Hi All,
I do not want to dampen our spirit of the Arduino.
Truly, it is a wonderful platform for many and
diverse uses. But, sometimes, simpler is better!
You can easily build a three-phase generator
with a single CMOS IC. According to Don Lancaster,
the 4018B counter can produce three square wave
signals spaced 120 degrees apart. Since it is purely
digital, the output frequency is easily varied by changing
the clock frequency (which must be 6 times the output
frequency). You can then filter the square wave outputs
via digital means to sine-wave approximation. (A motor is
quite tolerant of the wave shape.)
See Lancaster's book "CMOS Cookbook" for details and
circuits.
Herb
raschemmel:
That's how long it took me to think of an answer
Har! Thankfully I did not have a beverage in my mouth when I read that! 
Keyboard and monitor are both safe!