 MKP DC link capcitors in drsstc?
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Hartstart
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Mon May 30 2011, 06:31PM
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Registered Member #2616
Joined: Sun Jan 10 2010, 01:00PM
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Posts: 12
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Has anyone tried what happens if you replace electrolytic caps from bridge DC rail with modern high power MKP capacitors. New high power nverters have these already, 1000-1500VDC, 500-1500µF and 50-150A RMS. ESR is typically very low and ESL bit higher than commercial inverter grade lytics.
Having single cap capable of over 1000V is quite tempting. Currently my brick coil has 1700V bricks (CM300DU-34kA in H-bridge) and my DC rail voltage is currently around 800VDC.
Works fine but having series-paralled lytics mounted on top of igbts doenst look very good even from distance. (and has pretty high inductance)
My idea is to get couple ~750-1000µF +1000V link caps and pop them in parallel right on top of igbts.
Caps will be rapidly discharged during burst (no problem there, i guess) but charging them back to desired DC rail voltage during off time wont happen with just rectifier bridge. I have voltage doubler that has couple beefy lytics and i think i will move it under the coil as secondary energy source. Of course lots of decoupling caps and heavy wires :)
Main concern is ringing. To me High(ish) ESL and very low ESR doesnt sound very good idea in this kind of application. Electrolytics are known to dampen things down more or less but these caps may be different story.
Any suggestions?
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