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Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
Hello guys, I'm building my big coil, it uses a cm300dy-24h full bridge driven by two GDTs, one for each brick. I'm not sure about good rise and fall times..
I will not use phase lead for now so I need to care about voltage spikes over the brick. I was think something like 500ns of rise (-24v to 24v) and 300ns of fall (24v to -24v). The system will run at 40khz. What you think about?
Registered Member #2288
Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179
That should be fine, that equates to about 2% rising and around 1.5% falling which is well within the acceptable range for a DRSSTC since you will be switching ZCS (presumably this is for a DRSSTC). If you were to use a phase lead you might want to push it even faster (although you wouldn't be required to, I just like to switch in <100ns on a phase lead since the switch ringing is nearly eliminated, so why not reduce losses that much more... but switch ringing also usually becomes worse with faster switch times so without phase lead you need to balance what you gain by what is lost).
Registered Member #599
Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624
Some scope shots from my coil. CM300DY-24H full bridge, phase lead driver.
If my memory serves right im using 5ohm gate resistors bypassed with ultrafast diodes for faster turn-off. Single GDT is used.
This thing has been pushed to 1800Amps and and i have popped 16A breaker several times without killing IGBTs. And there is almost no heat at all (igbts have only 25mm tall heatsink and fan and it gets luke warm)
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
Ohh, thanks for your waves! hehehe. I see you have a big rise, ~1us and a 500ns fall.. but you are using phase lead.. I will try to get some times like it! Thanks!
And, for protection of the igbts at flash-over or primary strikes, I putted one 470nF capacitor at -Vbus to the RF ground. Are you using some capacitor here?
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cm300dy-24h rise and fall
