On Wed, Apr 06, 2011 at 08:49:16PM +0100, andy pugh wrote: > And now the cap sizing. > If I say that I can put up with 10% ripple at max rated current (7.5A > for the motors) on a nominal 300V then I end up with > C = 7.5A X 10mS / 30V = 2500uF. > > Eeek! > > http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5436785 > > Is the cheapest that is even close. > > A thread on CNCzone said 20,000uF per amp, but I decided to ignore that.
That _would_ be excessive at 400 odd volts. Your formula is good enough for engineers. The CNCzone thread is merely specifying 0.5v of ripple. Next he'll want the gold plated terminals and "oxygen-free" copper cables of audiophiles, perhaps. I thought it was just me who couln't find big low ESR caps at good prices. Erik -- Good judgement comes from experience. Experience comes from bad judgement. - Jim Horning ------------------------------------------------------------------------------ Xperia(TM) PLAY It's a major breakthrough. An authentic gaming smartphone on the nation's most reliable network. And it wants your games. http://p.sf.net/sfu/verizon-sfdev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
