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# [SOLVED]Problems with Inverter

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##### Junior Member level 3
Hello

I am working on inverter. I have some problems going with it.

Here is the code I am using. I am giving pulses from an ATMEGA162 Micro controller.

I am working on hardware. Final Hardware will be driven by another series of micro controller. So I am not very good with this code. I am applying +DC Bus of 30V

Problems I am having are:

IGBTs are getting very heated up.

a) I think by putting dead time, it will solve the problem. But I am not sure how to put it in this code. Any help

b) or if there is anything else which might be wrong with the inverter. Please do guide

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#define f 400
#define spc 24
#define Phase1L PORTC.0
#define Phase1H PORTC.1
#define Phase2L PORTC.2
#define Phase2H PORTC.3
#define Phase3L PORTC.4
#define Phase3H PORTC.5

flash unsigned char PWMCodes[721]={0,0,4,9,13,18,22,27,31,35,40,44,49,53,57,62,66,70,75,79,83,87,91,96,100,104,108,112,116,120,124,127,131,135,139,143,146,150,153,157,160,164,167,171,174,177,180,183,186,190,192,195,198,201,204,206,209,211,214,216,219,221,223,225,227,229,231,233,235,236,238,240,241,243,244,245,246,247,248,249,250,251,252,253,253,254,254,254,255,255,255,255,255,255,255,254,254,254,253,253,252,251,250,249,248,247,246,245,244,243,241,240,238,236,235,233,231,229,227,225,223,221,219,216,214,211,209,206,204,201,198,195,192,190,186,183,180,177,174,171,167,164,160,157,153,150,146,143,139,135,131,128,124,120,116,112,108,104,100,96,91,87,83,79,75,70,66,62,57,53,49,44,40,35,31,27,22,18,13,9,4,0,4,9,13,18,22,27,31,35,40,44,49,53,57,62,66,70,75,79,83,87,91,96,100,104,108,112,116,120,124,127,131,135,139,143,146,150,153,157,160,164,167,171,174,177,180,183,186,190,192,195,198,201,204,206,209,211,214,216,219,221,223,225,227,229,231,233,235,236,238,240,241,243,244,245,246,247,248,249,250,251,252,253,253,254,254,254,255,255,255,255,255,255,255,254,254,254,253,253,252,251,250,249,248,247,246,245,244,243,241,240,238,236,235,233,231,229,227,225,223,221,219,216,214,211,209,206,204,201,198,195,192,190,186,183,180,177,174,171,167,164,160,157,153,150,146,143,139,135,131,128,124,120,116,112,108,104,100,96,91,87,83,79,75,70,66,62,57,53,49,44,40,35,31,27,22,18,13,9,4,0};

void main(void)
{
unsigned char i=0,j=0,k=0;
DDRA=0x00;
DDRB=0x13;
DDRC=0x3F;
DDRD=0x10;

TCCR0=0x69;
TCCR1A=0x81;
TCCR1B=0x09;
TCCR2=0x69;
TCCR3A=0x81;
TCCR3B=0x09;

OCR0=0x00;
OCR1A=0x00;
OCR1B=0x00;
OCR2=0x00;
OCR3AH=0x00;
OCR3AL=0x00;
OCR3BH=0x00;
OCR3BL=0x00;

while (1)
{

for (i=0;i<spc;i++)
{
j=i+8;
k=i+16;
if(i<12)
{
Phase1L=0;
Phase1H=1;
}
else
{
Phase1H=0;
Phase1L=1;
}

if((j>11)&&(j<24))
{
Phase2H=0;
Phase2L=1;
}
else
{
Phase2L=0;
Phase2H=1;
}

if((k>23)&&(k<36))
{
Phase3L=0;
Phase3H=1;
}
else
{
Phase3H=0;
Phase3L=1;
}
OCR0=PWMCodes[(i+1)*(360/spc)];     // Output Phase#1 (OCR0)
OCR3AL=PWMCodes[(j+1)*(360/spc)]; // Output Phase#2 (OCR3A)
OCR2=PWMCodes[(k+1)*(360/spc)];   // Output Phase#3 (OCR2)
};

};
}

Last edited by a moderator:

#### Vbase

##### Full Member level 6
Hello

b) or if there is anything else which might be wrong with the inverter. Please do guide
If the microcontroller outputs are giving delays for on and no delay for off (most PWM do), these delays will cause overlapping by reversing the polarity of the signals by the optocouplers. Overlapping of the gates drives will cause the IGBTs to conduct together and overheat.
Try adding logic inverters or connecting the microcontroller outputs directly to the IR2112.I've illustrated the drive signals to show what I mean. The left shows signals that are never high together to avoid IGBT conducting together. This is normal signals from M/C.
On the right the signals are inverted as your optocoupler does. I marked the area that the IGBTs will conduct together.

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