control single phase induction motor using microcontroller

My project involves controlling a single phase induction motor using microcontroller. we are using microcontroller to drive igbt drivers which inturn drive four igbts. kindly help me how to proceed. I am a newbie in ckt design and microcontroller

To change the speed of an AC motor, you need to change the drive frequency. Your 4 IGBTs will form an H-bridge. You no doubt will need an H-bridge driver, then you only need to change the drive frequency.

Russlk said:

To change the speed of an AC motor, you need to change the drive frequency. Your 4 IGBTs will form an H-bridge. You no doubt will need an H-bridge driver, then you only need to change the drive frequency.

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only... you make it sound soo easy

yer you can do i that way, open-loop V/f control. IF you need a more accurate speed control (prolly dont) then a closed-loop speed controller will be needed

Varying the voltage on an AC motor will change the power factor but the motor runs at constant speed or not at all.

Russlk said:

Varying the voltage on an AC motor will change the power factor but the motor runs at constant speed or not at all.

Click to expand...

for a fix freq YES, but that isn't going to change its speed now is it? an induction machine's rotor velocity is related to the stator freq.
But for open-loop control of an induction machine V/f control is only slightly more complex then straight f control BUT gives you alot more stability.

For true speed control you would need a propper speed loop


So V/f control?
With V/f control, the voltage of the motor is dependent on the frequency defined by the V/f characteristic curve.
The voltage is applied to the motor and the current depends on the motor state.


Thus you have a ookup table of what RMS voltage you need to supply for a given freq to ensure the most stable open-loop speed control (which for an induction machine is bloody good).


So you somewhere have this lookup table with a SIN generator that is then used to create hte PWM to driver yr H-bridge

Request

can i have look over your circuit. if you wont mind

Hi there,


Actually, to vary the speed of an AC motor you have to vary the frequency but you also have to vary the voltage. If you lower the frequency you have to lower the voltage too or the laminations will saturate.
B=E*10^8/(4.44*F*A*N)

Using an H bridge and modulating in a sine pattern gives pretty good results without requiring any filtering.

Profile of user: sushant_el: Last Activity 6th December 2005 03:55 PM

Hi again,


Yes another old old thread