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Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Daniel Kramnik wrote ...
Quick correction - the RFUS20TF6S are rated for 20A average rectified current, but 100A pulsed. I think that this should be good enough to get started (at first, I'll have my OCD set to around 100 or 150A), but the question of heatsinking still stands. I only have 2 of these diodes left, so I don't want them to explode!
The diodes that are pared with the IGBTs should be rated to withstand the same pulsed and slightly less RMS current that the IGBT would see. At Least I think so. The reason behind this is because at the end of your burst there is going to be left over energy in the tank circuit and that energy has to go somewhere. This energy will oscillate at the same frequency and start out at the same current level that was present when the burst ended.
So where dose this oscillating left over energy go you ask? It gets rectified by the diodes antiparallel to you IGBTs back in the bus capacitor. So it is important to have the diodes rated to switch as much power as you plan to push through the IGBTs.
Also about over driving the gates. I don't think you need to drive the gates to 33V. You should be able to get a very respectable output will running the IGBTs at there rated gate voltage. Over driving the gate in my opinion is just a good way to make your coil a lot more unreliably. If you are looking for reliability which I think you are, then drive at a more modest 24V.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
ScotchTapeLord wrote ...
If you set the OCD to 100-150 then 24V is probably more than enough gate voltage.
For 100-150A, even 10V is enough, according to the datasheet. 100-150A seems a bit low when considering performance, however. How much primary current you should use depends on how much the IGBTs can handle, and this is a hard question to answer.
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
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Posts: 226
Please, don't overdrive the IGBT gate at 33v, put 24v with a 5r resistor, is the best you can get with this devices. You can try use a high impedance LC tank circuit, it will give low RMS current, will not blow yours IGBTs, but with higher tON iterrupt time you will get the same performance, power.
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Overdriving Gates on ISOPLUS IGBTs
