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controller 3 phase motor with PWM

 
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filjoa



Joined: 04 May 2008
Posts: 260

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controller 3 phase motor with PWM
PostPosted: Thu Oct 22, 2009 4:56 am     Reply with quote
hi

I need controller 3 phase motor with PWM, I connect my PIC on IRF and it close circuit with an resistor (10Ohm/ 150W) to brake motor (reduce speed)...

But how I can know value of PWM?

I have this configuration on my program:
Code:

setup_ccp1(CCP_PWM);       
setup_timer_2(T2_DIV_BY_4, 255, 1);
(...)
set_pwm1_duty(0); //max speed
set_pwm1_duty(255); //min speed

I don't know how frequency I stay work with PWM.

PS: I use PIC18F252 with clock 20Mhz

best regards
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Oct 22, 2009 12:02 pm     Reply with quote
PWM frequency forumla:
http://www.ccsinfo.com/forum/viewtopic.php?t=17993
filjoa



Joined: 04 May 2008
Posts: 260

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PostPosted: Thu Oct 22, 2009 5:16 pm     Reply with quote
Hi

My frequency with this configurations is 4901hz correct?

I test it and I have very noise when I try set_pwm1_duty(1) at set_pwm1_duty(175).

How I can reduce this noise?

PS: I think put frequency more than 20Khz but I don't know how make that.

best regards
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Oct 23, 2009 2:33 pm     Reply with quote
Quote:
My frequency with this configurations is 4901hz correct?

That's close enough to the calculated frequency.

Quote:
I test it and I have very noise when I try set_pwm1_duty(1) at set_pwm1_duty(175).

How I can reduce this noise?

I don't know what you mean by "noise". You should see a clean pulse
on the oscilloscope.

Quote:

PS: I think put frequency more than 20Khz but I don't know how make that.

Did you take Algebra ? Use the equation in the link that I gave you.
Set the Timer2 Divisor value to 1, in the setup_timer_2() function.
Then solve the equation for PR2. It will give you the value to use
for the middle parameter in setup_timer_2().
filjoa



Joined: 04 May 2008
Posts: 260

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PostPosted: Fri Oct 23, 2009 6:14 pm     Reply with quote
Hi

noise is "iiiiiiiiiiiiiiiii" when I try break motor...

I have must algebra... but I don't know with is possible use divide timer for 1. I don't read this part of the post...

But now stay all ok, thanks
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