Here's what I did for my DC Servos. The external micro-controller sets a timer after it starts up and when the timer is done it asserts the control to close the relay. The closed relay information is fed back to the Break Out Board to signal the motor drivers that High Voltage motor power is now stable. John
> -----Original Message----- > From: Thaddeus Waldner [mailto:thadw...@gmail.com] > Sent: August 6, 2024 5:46 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Question to electrics gurus: Correct setup for > rectifier + capacitor > > Some designs fill the capacitor through a small resistor, then turn on a relay > once the voltage is up. Drive operation needs to be inhibited during the fill > process. > > > On Aug 6, 2024, at 4:21�PM, Chris Albertson > <albertson.ch...@gmail.com> wrote: > > > > ?The capacitor is charged when the switch is closed. A huge current will > flow into the capacitor until it is �full�. The usual solutions are to (1) > use a > slow-blow fuse that can withstand the surge current or place a low value > power resister in series with the AC to limit maximum current. Inductors > can do this better than resistors. > > > > Also it might just be luck. When you switch high-current AC, it is best to > switch on the zero crossing when there is zero volts. Unless there is a > circuit > to make that happen it is just luck what the volts are when the contacts > close. Most poweerful AC powered heaters are switched usung a solid state > relay and these are designed to switch on zero. Domestic water heaters and > resistive building heat is all done this way. > > > > > >>> > >>> > >>> I do not understand why was everything fine in initial testing - I did > >>> turn machine on and off lots of times and capacitor was discharged > >>> (and recharged!!!) numerous times. I have swapped that fuse for > >>> identical unit from a machine that has yet to go through the retrofit > >>> process. And it is the same. > >>> > >>> So my question to electronics gurus - could capacitor be damaged or > >>> was it just a beginners luck that everything worked and do I need to > >>> introduce some inductor between rectifier bridge and capacitor to > >>> limit the startup current that charges capacitor? > >>> > >>> Viesturs > >>> > >> > >> Typically a NTC is used to limit the surge current, either in the AC line > >> or the DC between the bridge and the filter capacitor. Here is a NTC > manufacturers page on this usage: > >> > >> https://product.tdk.com/en/techlibrary/applicationnote/howto_ntc- > limiter.html > >> > >> > >> > >>> > >>> _______________________________________________ > >>> Emc-users mailing list > >>> Emc-users@lists.sourceforge.net <mailto:Emc- > us...@lists.sourceforge.net> > >>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>> > >> > >> Peter Wallace > >> Mesa Electronics > >> > >> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net <mailto:Emc- > us...@lists.sourceforge.net> > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users
LoadShunt.pdf
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