On Wednesday 03 January 2018 11:03:05 Dave Cole wrote: > Some of the "Driveswarehouse" type places sell solid state "phase > converters" that have no speed control, but they seem to cost as much > or more than the equivalent sized VFD. No idea why. It must be > driven by the marketplace. > I suppose if all you are driving is a blower or pump then having > onboard braking circuitry might be close to worthless. > The Estop requirements on most automation machinery requires a rapid > stop on all rotating machinery. > So... is anyone going to buy the $125 5 hp drive and let us know how > long it lasts before the drive goes "pop". ;-) > > Dave
Well, so far and definite not in a production environment as I cut lots of air before making swarf, my cheap, break resistorless clone, has managed to protect itself from everything I throw at it, and I have a g33.1 peck cycle test run that never finishes, I use it to tune the bits and pieces of the vfd for the fastest reversal at the end of the instroke, or at the other reversal at the end of the outstroke, and have succeeded in getting it down to just over 3 turns of the 3 jaw chuck at the bottom of the hole at 300 rpms. Correspondingly slower with the 8" 4 jaw mounted. If the hole is blind, I'll convert the encoder counts shown by my hal code capture into turns, then from that inches or mm's, and edit the code to shorten the instroke by that amount. A ready source of quality blind taps is a plus, most of mine aren't. Quickness of turnaround is a balancing act of how fast you can actively slow it without an overvoltage trip with that sensitivity riseing quickly with the rpms, and how long you leave the dc braking on and at what amperage. This latter is in time and amps so if you turn that up, but are only turning 75 rpm, you waste a lot of time at a slowly oozing stop before it actually begins the accel in the other direction. Some what of a damned if you do, and damned if you don't. I get the impression that if this one had the rs485 port mentioned in the manual, but there are no places called out on its logic board to even connect one, that this type of thing could be done much more intelligently by the driver while it was actually running the motor by customizing all this to the rpms being turned. This could convert the reversal into a stanza of code at least as complex as a tool changer robot driver, but quicker than it can do now when one must negotiate your way thru the pushbuttons on the panel to change anything in what IMO, should be totally under linuxcnc's control, but the best I've got is a Spin-X1, no rs485. I have a corcom brick wall filter to keep its noise from bothering the other line powered stuff, on the line side of the vfd. On this machine, linuxcnc is the motor power control thru some 40 amp SSR's. Works well and theres no huge and clunky drum switches in sight. The 7i90, thru the 7i42TA's, has no problem controlling the SSR's. Given that I'm not dealing with a 5hp motor, this $130 1.5 hp rated single phase 254 volt src vfd, running an elderly 1 hp 3 phase 230 rated motor, is giving me good value for the money. It is, considering the difficulty of the job, getting the job done. I bought two of these motors off an air compressor, retired after after 40 years without much weather protection during a remodel at the local horsepistol. $50 bucks for the pair, and 4 new bearings, only 2 have been used, so I have one in the bottom of the Sheldon, and a ready to roll spare in case for about $75 bucks. Whats not to like? Would I buy another if I had a need? Paypal just works. > On 1/2/2018 6:35 PM, Gregg Eshelman via Emc-users wrote: > > I run the VFD (that's never varied) on my old Monarch lathe without > > using braking. It has terminals to connect a braking resistor but > > for this machine there's no need. > > > > What I find crazy is that a simple, single function device that only > > converts single phase to three phase, without all the fancy features > > of a VFD, costs so much more than a VFD. When a 3HP VFD for > > 220~240VAC input can be had for under $300, why isn't a version that > > does absolutely nothing, no adjustments, no variation, no > > programmability, but do the phase conversion not cost well under > > $200 instead of a whole lot more? If some company produced a box > > that was just a phase converter with an on/off button and terminals > > for a remote switch as the only 'extras', and put a $199.99 price on > > it, they'd be hard pressed to keep up with demand. > > > > On Tuesday, January 2, 2018, 9:33:50 AM MST, Dave Cole > > <linuxcncro...@gmail.com> wrote: > > > > So what exactly do they do when the bus voltage rises during decel > > ?? Or is there no decel control at all? > > I've never seen a drive without braking circuitry and DC bus voltage > > control. > > -------------------------------------------------------------------- > >---------- Check out the vibrant tech community on one of the world's > > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ---------------------------------------------------------------------- >-------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
