September 28, 2011

Power Inverter design(Proteus Simulation)


Hello friends
Rright now I am working with induction furnace as a final year project.
As a part of that I am working on an inverter made up of H-bridge connection of Power MOSFETs.

you can read more about MOSFET triggering circuit from here. 

You are reading this ,means you should also be interested in  PWM control of Inverter.
Basic connection of an inverter would be as shown in figure below….

If s1 and s4 are on current through load is positive.

If s2 and s3 are on current through load is negative.

Be careful about simultaneous conduction of s1 and s2 or s3 and s4 if either are conducting simultaneously you will end up with something blown either it is fuse of lab or your own design..:(
we can come up the short circuit by "crow bar circuit"but that is not discussed here..
Now comes the most challenging work generation of gate pulses for MOSFETs.

As I know that my load(in future)is inductive in nature so I have to design it including “zero voltage freewheeling”.
The pulses that  I have to generate are shown below this fig is taken from Power electronics by Joseph Vithayathi.


The method of generating these pulses is shown below.




I have used microcontroller (My favorite AVR Atmega 8535 )to generate Ramp wave.
Code to generate ramp wave of 10 KHz is given below(crystal freq is 16MHz)
include<avr/io.>
#include<delay.h>
void main()
{
DDRB=0xFF;      
unsigned char i=0;
while(1)
{             
PORTB=i++;
asm("nop");
asm("nop");
}
}


Then the wave is fed to a comparator, the reference voltage is  given with the  help of a  potentiometer user can adjust it.




you can see the pwm changing with reference to the DC level changed by user.. 





after connecting this stage to the Flip Flop stage we can observe these waveforms


after applying these gate pulses to MOSFET (IRF640)we can see the changing direction of current through the load branch...







the codes for generating ramp wave and ISIS Proteus design can be found from here.

that's all for this post friends next I'll post what difficulties i faced in implementing this ISIS design to reality.


feel free to comment


:)

2 comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...