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Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
a V-switch circuit will shut off an SCR without turning off the power, but it requires a second SCR and a smaller capacity capacitor. An IGBT would probably be simpler for your case though.
Registered Member #4451
Joined: Fri Feb 17 2012, 05:51PM
Location:
Posts: 16
How about this one. 500V DS, 100 amp continuous. Maybe this is overkill. If I am discharging caps and the current is very momentary, do I need that high of a rating?
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
You can buy thyristors for a couple of bucks which can handle that ... BT151 for instance (easier to search on digikey by the way, they allow you to select on surge current).
Registered Member #4451
Joined: Fri Feb 17 2012, 05:51PM
Location:
Posts: 16
Thanks guys! Never used one of these. It looks like a thyristor would be a really cheap and compact method. Since they are cheap enough, I will probably go with a 200A breakover current and 600V rating, like the TYN616RG. I think links are disabled, but Ill try to post the datasheet.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
NoName wrote ... How are you guys getting those current calculations?
Here's a popular online calculator. It draws damped sin (and optional cos) waveforms, whose coefficients come from elementary LCR theory. Result in your case agrees with that given by "wolfram".
Note that if your switch is an SCR, your capacitor will be left with charge of 70 volts and reversed polarity. Search the "projectile accelerator" forum here for remedies.
Registered Member #834
Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644
Note that at these absurdly high current levels the core of the solenoid surely saturates, the inductance drops to the air-core level, and the current rises even more. The 1N4007 alone would protect the mosfet, but its maximum current (for long time) is just 1 A. More turns on the solenoid are a simple solution.
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HV dicharge through inductor killing my irf840!
