On Wednesday 28 July 2021 23:08:48 John Dammeyer wrote: > Gene is right. The input surge from transformers and capacitors can > be quite major. To get around that I build a couple of circuits to > slow down the input surge and to also clamp over voltage from > decelerating DC servos plus drain the caps of the 105VDC quickly so > that it was safe to work on. > > http://www.autoartisans.com/mill/drawings/MillCNCDrawings.html > > The above link is to my dirty laundry so to speak. Essentially I put > a 47 Ohm 10W resistor in series with the primary winding on power up.
It will also serve as a fuse in the event the circuit malfunctions :) My 200 watter will survive if one of the SSR's shorts. Or fails to trigger. And is simpler as well because except for the SSR's, its all in the .hal recipe. In fact on that machine, I'm doing it twice as I also limit the first seconds inrush to the switching supplies that run all the steppers and servo's on that machine. Again using a scrap box part, in that case a 10 ohm 70 watt but the rest is the same. I'm a great fan of having leftover i/o pins specifically so I can do such tricks as the need arises. > How long it's there is based on the PIC controller that also runs the > high voltage clamp and drain circuit. > I haven't worried about that surge at reversal time, it hits about 170 volts, but since its used up re-accelerating the motor in the reverse direction, the 130 volt rating of two 65 volt caps in series has been totally not a problem as the overvoltage is gone again in 50 to 75 milliseconds. The caps, being electrolytic, may in fact leak at that point but its such short term there is no detectable heating. Basically it just serves to keeping the caps well formed. Been doing it for 5 or 6 years now. In fact, I've had to profile that turnaround, slowing it some, to get rid of the z following error because it can't reverse direction as fast as the spindle can, by running the drive to the pwmgen thru a limit3. The actual direction change is held up until the motor is stopped. And I can still reverse the spindle at 3000 rpm in <400 milliseconds. hal is a very helpful tool, you could even have it make your coffee. That wouldn't be any more complex than coding up a tool changer. > John Dammeyer > > > -----Original Message----- > > From: Gene Heskett [mailto:[email protected]] > > Sent: July-28-21 3:24 PM > > To: [email protected] > > Subject: Re: [Emc-users] Lathe Spindle Drive Questions > > > > On Wednesday 28 July 2021 15:25:01 Chris Albertson wrote: > > > Do you really need to worry about inrush tripping the breaker? > > > 1) If the DC supply is the old linear type, it will have a very > > > large filter capacitor and supply peak loads without a large AC > > > draw. The trick is to turn on the supply and then the motor a > > > second later. > > > > Now, imagine that supply consists of 4 toroid transformers each > > capable of developing the nominally 63 volts plus and minus, for a 1 > > kw analog audio amp. and the filter caps are 6 in each supply of > > 9200 uf at 65 volts, and each transformer is treated as a single > > supply. wired two in parallel and two tall for a combined voltage of > > around 126 volts and 220800 uf. Plug that into a 30 amp breaker and > > flip the switch. clunkiest switch you ever heard because that 30 amp > > breaker went down like a shotgun on the first half cycle of power, > > essentially simultaneous with the click of the switch. So I hit the > > junkbox and come up with two 40 amp SSR's and a 50 ohm 200 watt > > resistor, added a couple time delays controlled by hal and driven by > > the F2 state such that the 50 ohm is in series with the supply line > > for the first 4 seconds and is shorted after that. Now it runs fine > > on a 15 amp breaker, but will trip it if I ignore the motors > > chirping because the pwm-servo is set to about 17 amps but it takes > > several seconds, so I settled for a 20 amp in that slot. > > > > And for Ralph's problem with the Washington inspectors, I suspect > > they are reading the rules wrong, here they don't care about the > > load, the only thing they checked outside of the box was the ground > > wiring to the rods. > > > > And for lack of any other pressing duties, helped me bore 2 holes > > thru about 8" of green concrete the required 6 feet apart to make it > > meet code. After he ok'd hooking up the drop so we had power to run > > the hammerdrill. > > > > Cheers Chris, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > If we desire respect for the law, we must first make the law > > respectable. - Louis D. Brandeis > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
