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Switching GTO thyristor for 3-phase inverter

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pns2050

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Hello,

I am trying to do my Senior year project which is a DC to three phase AC inverter.
I am trying to achieve that using Gate turn off thyristors(BT-157) and PIC16f88 for triggering.

The problem is that PIC does not output negative voltage which is needed to turn off the GTO thyristors.

I tried to use an op-amp(LM741) in inverting mode to inverse the polarity of PIC's output , which indeed seemed to work on oscilloscope but when i tried to turn off/on the thyristor's the results weren't positive.

Would it be possible to control them the way i am trying or should i look to another direction ?

I really spent a lot of time trying to figure this out and cant get it to work , any Hint/Idea would be appreciated.

Thank you
 

Why you would like to use such a component, as there may be alternatives (IGBT)?

The "problem" with GTO is that you need to pull lots of current out of the gate (during short time) to get it in the off-state again. This requires you to drive the gate below cathode level.
 

In my university they already did a single phase inverter using IGBT , so my Supervisor wanted to do it using thyristor's and also making it three phase. I found it interesting so i started this idea.

Are you saying it is not possible to have the desired output using the current components ?
 

pns2050 said:
Hello,

I am trying to do my Senior year project which is a DC to three phase AC inverter.
I am trying to achieve that using Gate turn off thyristors(BT-157) and PIC16f88 for triggering.

The problem is that PIC does not output negative voltage which is needed to turn off the GTO thyristors.

I tried to use an op-amp(LM741) in inverting mode to inverse the polarity of PIC's output , which indeed seemed to work on oscilloscope but when i tried to turn off/on the thyristor's the results weren't positive.

Would it be possible to control them the way i am trying or should i look to another direction ?

I really spent a lot of time trying to figure this out and cant get it to work , any Hint/Idea would be appreciated.

Thank you
Click to expand...
u can hold the gate with a fixed neg bais and the pic will override it by pos pulses , any way the neg supply phase will shot off the gto . see link**broken link removed**
 
Last edited:

I am gonna try this ..

Any more ideas? Using op-amp in inverting mode will not make it work ? By my small experience it doesn't but i could be doing something wrong..
 

Very likely you are not able to pull sufficient current out of the gate to turn it off fast enough, as the "gate turn off gain" is low. If you are running at 2A anode current, you may require a negative gate current pulse of over 0.5A to break the latching condition fast enough.

You definitely need to know the operation of the GTO thyristor before using it. Try a search with: gate turn off thyristor gain
 

WIM...PNS..
Please check out my link posted and u will understand.
now your problem is how r u going to gate six 6 GTO ALL GATES ISOLATED FROM EACH OTHER.
the answer is 6 opto isolators .
 

dselec thank you, i will read this in detail and give it a shot..
I will post any result i get
 

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