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need help: speed control of 3 phase induction motor using triac

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mtwieg said:
You'll want to keep the PWM frequency high; 20KHz is nice since it shouldn't generate audible noise, though depending on the power you want to deliver you may want to adjust it up or down. For the motor speed that's variable and you should only be limited by the motor itself and your bus voltage, and maybe your control system.
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one more question what will happen if i change the frequency and keep duty cycle constant??and vice verse???

hi i tried this driver circuit but my ir2110 start heating, what is the problem?? how can i check the output of driver with out connecting the mosfet?? 70_1312784222.png
 

malik_zohaib said:
one more question what will happen if i change the frequency and keep duty cycle constant??and vice verse???
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Changing the PWM frequency shouldn't significantly change anything, except maybe circuit efficiency.
hi i tried this driver circuit but my ir2110 start heating, what is the problem?? how can i check the output of driver with out connecting the mosfet??View attachment 62186
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First the pulldown resistor R6 is going to drain your bootstrap capacitors pointlessly. You should change both R6 and R7 to be more in the range of 10K-100Kohm. Also make sure you have sufficient dead time on your outputs (that inverter circuit on the input of the IR2110 may cause cross conduction on the rising edges of you PWM).
 

mtwieg said:
Changing the PWM frequency shouldn't significantly change anything, except maybe circuit efficiency.
Click to expand...

and what will happen when i change duty cycle while keeping frequency constant???
thanks i will change the resistor value and then let you know. and what about o/p voltage testing??without mosfet??

one thing more can i use diode in parallel to gate resistor to insert dead time???
 

hi guys one thing more; what will happen if i short the h and l input of the ir2110 (provide the same pwm)???
i have a very little knowledge about the driver ic. please clear my doubts.
thanks
 

hi guys can someone explain this:
when i connect vdd of ir2110 to 5v and vcc to 12v and apply pwms, it start burning. and when i applied the 12v to both of them and increasing the pwm voltage from 5v to 12v the ir2110 is giving me the output without overheating. is it normal???
and also when i short the drain and source of irf540n then i get 0volt at output and 0v at h0 of driver, why?
 

malik_zohaib said:
hi guys can someone explain this:
when i connect vdd of ir2110 to 5v and vcc to 12v and apply pwms, it start burning. and when i applied the 12v to both of them and increasing the pwm voltage from 5v to 12v the ir2110 is giving me the output without overheating. is it normal???
Click to expand...
No, something is wrong with the IC, or you have something connected incorrectly. Try to determine where exactly the current is flowing which causes the heating. Make sure you are using the COM and VSS pins appropriately.

I've found that the vast majority of issues people have with these chips are due to just not reading the documentation thoroughly. IR has some detailed app notes you should read before continuing:
http://www.irf.com/technical-info/appnotes/an-978.pdf
http://www.irf.com/technical-info/appnotes/an-1092.pdf
They also have one specifically on the kind of 3phase inverter driver chips you were trying to use at first:
http://www.irf.com/technical-info/appnotes/an-985.pdf
 

thanks mtwieg.

but i tried the circuit of an-985 with microcontroller. but i short circuited the gnd of the pic board and the gnd of inverter, and i used the 470uf/50v electrolyte capacitor across ir2130. when i power the circuit after few seconds the cap just below up!!!!!!!!!!
can you explain this??? or i am making mistake by shorting the gnd together.????

regards.
 

but i short circuited the gnd of the pic board and the gnd of inverter
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Why "but"? Having a common ground between driver logic input and inverter is required for IR2130 and all similar gate driver ICs. There must be another problem in your circuit. Without knowing the exact circuit, we can only guess.
 

malik_zohaib said:
thanks mtwieg.

but i tried the circuit of an-985 with microcontroller. but i short circuited the gnd of the pic board and the gnd of inverter
Click to expand...
Normally these should be shorted together in the circuit, as FvM says. The driver IC also has separate ground pins, some meant for the logic supply, and some meant for the driver side, which are normally shorted together. Make sure you use all of those pins, or it won't work.
and i used the 470uf/50v electrolyte capacitor across ir2130. when i power the circuit after few seconds the cap just below up!!!!!!!!!!
can you explain this??? or i am making mistake by shorting the gnd together.????

regards.
Click to expand...
You have to explain what you mean by putting a cap "across" the ir2130. Which nodes did you connect it to?
 

mtwieg said:
Normally these should be shorted together in the circuit, as FvM says. The driver IC also has separate ground pins, some meant for the logic supply, and some meant for the driver side, which are normally shorted together. Make sure you use all of those pins, or it won't work.
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yes i am using all these pins. i just put the cap across vcc and vss to remove any transient affect.
have you seen the circuit on page 7 of doc an-985??? this is what i did.
 

have you seen the circuit on page 7 of doc an-985??? this is what i did.
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In this circuit, the VCC bypass capacitor won't "blow up", if connected with correct polarity. So either your real is circuit is different somehow, or your gate driver IC had already an internal short before, e.g. due to previous "mistreatments".
 

FvM said:
or your gate driver IC had already an internal short before, e.g. due to previous "mistreatments".
Click to expand...
how can i test the ic??? just apply the power and lin, hin signal and check the respective o/p, is it right??
 

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