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Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
Hi all, I was noticed here, that my IGBT's blow every time I get a ground strike, the arcs gets orange when it gets to the ground. I think it blow because current, but when I was in the IRC, setting up my drsstc, some people have helped me (I dont remeber the nickname) how to make the CT work. Ok CT is working but the Primary current is VERY low, because it only starts at 30VDC Bus and with 10k Bleeding resistor with a 1:1000 CT. I dont have a scope so I cannot measure the current, but I was thinking about, My Primary cap is 50nF and the Inductor is 8.5uH, its a small coil.
Is there other way to I measure the primary current? I want to make a overcurrent protection but I dont know the current. (Its at perfect tune, I have measured, the primary is running at 244Khz so the secondary.)
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
That person was me Glad to hear you got it working. I think that your feedback signal isn't strong enough. At what input voltage do your igbt's start to blow.
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
It blowed at maximum power, 128Vac mais with doubler. It gets 300VDC at Main bus. But all the times that I have tested my drsstc it was blowed when it striked to ground many for some long time. About the signal, that is correct, I think primary current is too low when running at low power. But actually it was worked perfectly until started to get strikes to a grounded target.
PS: Thanks for the help Dalus! That is the first time that I get the CT working :D
Registered Member #639
Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512
I think you will need a way to measure the current to diagnose the problem. But i can't think of a way to measure the peak current in the primary without an oscilloscope. Your IGBT's could also die from overvoltage, are you using transient voltage suppressors?
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
15V clamped by two 15V Zeners. The drivers are with 15V Stabilized Power Supply. The GDT loses are near zero (I think) because I get a very high frequency core (VHF Range) lol
Registered Member #989
Joined: Sat Sept 08 2007, 02:15AM
Location: São Paulo, Brazil
Posts: 476
I doesnt matter after 15V, the IGBT's saturates for complete with 15Vge, so More of that will make nothing of it. And I have a 18V peak at turn on, that the Zeners doesnt clamp because its too fast for it, more than 20 will blow the gate of igbt.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
[blockquote][i]
15V is OK if you run the IGBT within the peak current rating given in the datasheet. IF you exceed this rating, you will want more gate voltage to ensure the IGBT remains saturated, and does not de-saturate from the higher currents with insufficient gate charge. Look at the output characteristics vs gate voltage graphs to get a good understanding of how this works.
I suspect there is probably a grounding issue, or your setup simply isnt robust as it operates now.
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Ground strikes at DRSSTC
Glad to hear you got it working. I think that your feedback signal isn't strong enough. At what input voltage do your igbt's start to blow.
