Discharge a huge voltage
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From: lerameur on 3 Mar 2010 20:16 hello, I have a very simple circuit here, I am charging a 900uF capacitor to 600v. (900v max capacity) I want to discharge this at 0.01seconds interval. I have 30 ohm resistance, without so from my calculation I should have 20 amp max. All this element are in series with each other, I want to add a transistor (or mosfet) to make and break the intervals I need. DO I need to get a 600v and a 20 amp rated transistor ? Thanks
From: John Fields on 3 Mar 2010 21:01 On Wed, 3 Mar 2010 17:16:23 -0800 (PST), lerameur <lerameur(a)yahoo.com> wrote: >hello, > >I have a very simple circuit here, I am charging a 900uF capacitor to >600v. (900v max capacity) >I want to discharge this at 0.01seconds interval. I have 30 ohm >resistance, without so from my calculation I should have 20 amp max. >All this element are in series with each other, I want to add a >transistor (or mosfet) to make and break the intervals I need. >DO I need to get a 600v and a 20 amp rated transistor ? --- At the very least, yes. But... There will be inductance in the circuit, so depending on how fast you turn off the current into the load, L dI E = ------ dt might eat your lunch. JF
From: Sjouke Burry on 3 Mar 2010 21:03 lerameur wrote: > hello, > > I have a very simple circuit here, I am charging a 900uF capacitor to > 600v. (900v max capacity) > I want to discharge this at 0.01seconds interval. I have 30 ohm > resistance, without so from my calculation I should have 20 amp max. > All this element are in series with each other, I want to add a > transistor (or mosfet) to make and break the intervals I need. > DO I need to get a 600v and a 20 amp rated transistor ? > > Thanks Always apply a safety factor, I would use 800 and 30. Whether the 30 amp is needed depends on your duty cycle, if the dutycycle is low, 20 and even 10 might be enough. Just check the allowed peak current.
From: Hammy on 3 Mar 2010 21:20 On Thu, 04 Mar 2010 03:03:26 +0100, Sjouke Burry <burrynulnulfour(a)ppllaanneett.nnll> wrote: >lerameur wrote: >> hello, >> >> I have a very simple circuit here, I am charging a 900uF capacitor to >> 600v. (900v max capacity) >> I want to discharge this at 0.01seconds interval. I have 30 ohm >> resistance, without so from my calculation I should have 20 amp max. >> All this element are in series with each other, I want to add a >> transistor (or mosfet) to make and break the intervals I need. >> DO I need to get a 600v and a 20 amp rated transistor ? >> >> Thanks >Always apply a safety factor, I would use 800 and 30. >Whether the 30 amp is needed depends on your duty cycle, >if the dutycycle is low, 20 and even 10 might be enough. >Just check the allowed peak current. If he is saying > " (900v max capacity)" Shouldnt he be useing a 1kV-1.2kV fet or IGBT with maybe a drain clamp?
From: Sjouke Burry on 3 Mar 2010 21:36
Hammy wrote: > On Thu, 04 Mar 2010 03:03:26 +0100, Sjouke Burry > <burrynulnulfour(a)ppllaanneett.nnll> wrote: > >> lerameur wrote: >>> hello, >>> >>> I have a very simple circuit here, I am charging a 900uF capacitor to >>> 600v. (900v max capacity) >>> I want to discharge this at 0.01seconds interval. I have 30 ohm >>> resistance, without so from my calculation I should have 20 amp max. >>> All this element are in series with each other, I want to add a >>> transistor (or mosfet) to make and break the intervals I need. >>> DO I need to get a 600v and a 20 amp rated transistor ? >>> >>> Thanks >> Always apply a safety factor, I would use 800 and 30. >> Whether the 30 amp is needed depends on your duty cycle, >> if the dutycycle is low, 20 and even 10 might be enough. >> Just check the allowed peak current. > > If he is saying > >> " (900v max capacity)" > > Shouldnt he be useing a 1kV-1.2kV fet or IGBT with maybe a drain > clamp? He knows best, just apply some safety factor over the highest expected values. |