speed control of an motor by V/f method using pic16f877

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NitinPK

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My project is speed control of an ac motor by v/f method. We have to get variable voltage and variable frequency output which will be given to an ac motor. We are using IGBT H- bridge. Using pic16f877 we have to generate the pwm signals which drive the inverter. Can anyone plz help, how to generate pwm signals which will give the variable frequency and voltage? Thank you.
 

if you are a beginner then PIC CCS/mikroC is a good option
there are many in built functions for PWM,timer ... etc

in hardware section use a opto-isolator between PIC and IGBT driving circuit.
 

Thanks for the reply. Yeah am using the isolation part. But i wanted to know how to get the variable freq. and voltage and the how to generate the pwm pulses for the same.

- - - Updated - - -

Thanks for the reply. Yeah am using the isolation part. But i wanted to know how to get the variable freq. and voltage and the how to generate the pwm pulses for the same.
 

PIC -CCS
SETUP_CCP1();
setup_power_pwm(PWM_CLOCK_DIV_4 | PWM_FREE_RUN | PWM_DEAD_CLOCK_DIV_4,1,10000,1000,0,1,0);
set_pwm1_duty(duty);
 

Jestin_cubetech said:
PIC -CCS
SETUP_CCP1();
setup_power_pwm(PWM_CLOCK_DIV_4 | PWM_FREE_RUN | PWM_DEAD_CLOCK_DIV_4,1,10000,1000,0,1,0);
set_pwm1_duty(duty);
Click to expand...


hello dears ...

can you elaborate ..further ... because i am also trying to do variable frequency and variable voltage for Single phase 220V motor Speed control, Using PIC16f877.

i am struggling to do this ..
Please help me ...

i need of Only pwm parts .. remaining i will take care ..

thanks
madhu.
 

Hello nitin..

are got reply for the same ? share with me ..boss ..

hello jestin..can you share the code for V/F control
 


hi madhu hegde

what do you mean by variable frequency ?
PWM generation basics
1, PWM duty cycle
2, PWM time period

in most case PWM time period is fixed.
 

follow this link which exact answer of ur question

ww1.microchip.com/downloads/en/AppNotes/00889b.pdf
 

jestin is right PWM (Pulse With Modulation ) of CCP module generates fixed frequency with variable duty cycle square wave.

so first decide fixed frequency with variable duty cycle or only variable frequency..
 

Venkadesh_M said:
Here is the files for generating sine wave with pwm in pic micro controller.. Change the program to generate different v/f...
https://www.edaboard.com/threads/297108/
Click to expand...

Hell Dears..All.

i want control the speed of Single phase motor , means i have to generate 3phase pwm output with 2-pahse should be with 120Deg phase shift another one is 90deg phase shift .

with this i need Variable voltage with Variable frequency output , and also called V/F .

this is i needed , if any one done this with PIC16f877 ?

please share me only code ... power section will take care .
 

hi-tech c code for variable PWM time period

Code: 
#include<pic.h> 
#define _XTAL_FREQ 20000000


int time_prd=255,tmp;
unsigned char PRESCL=4;
unsigned long freq;


pwm_periode(char pwm_prd,char prescl)    //prescl 1/16/4   default 1  
{
PR2=pwm_prd;
time_prd=pwm_prd;
if(prescl>4)
{
T2CKPS1=1;       //PRESCLAR VALUE 1:16 
T2CKPS0=1;
PRESCL=16;
}
else if(prescl>1)
{
T2CKPS1=0;       //PRESCLAR VALUE 1:4 
T2CKPS0=1;
PRESCL=4;
}
else 
{
T2CKPS1=0;       //PRESCLAR VALUE 1:1
T2CKPS0=0;
PRESCL=1;
}
TMR2ON=1;
}


void freq_disp()
{
float tmp1;
//  PR2 = ( ( 1/pulse frequency in Hz ) / ( 1/clock speed x 4 x prescaler value ) ) - 1
//F= _XTAL_FREQ/(4*PRESCL*(1+PR2))
tmp1=4*PRESCL*(1+time_prd);	
freq=_XTAL_FREQ/tmp1;                 //frequency 
}
 

hello jastin .

is it for 3 phase sine pwm with v/f .?

i need of 3 phase , in that one should be 90Deg phase shift . Because i am doing controlling of Single phase motor , you can see this Application note - noarail.com/members2/d/3907-2/AN967A.pdf , Author: Padmaraja Yedamale.

please help ...
 

Hello JAstin .

yes i have seen this , but this is for 3-phase induction motor, not for Single phase induction motor .

i am giving little troubling you , so sorry . please check this ..Application note - noarail.com/members2/d/3907-2/AN967A.pdf

in that Figure no -5 , That is i wanted ,
can you help me .
 

Hello Jastin .

i try to program the asm code with PIC16f72 ... but lot of error is comming . can you help me
 

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