On Saturday 24 January 2015 13:55:39 Dave Cole did opine And Gene did reply: > On 1/24/2015 1:27 PM, Gene Heskett wrote: > > On Saturday 24 January 2015 11:49:20 Kirk Wallace did opine > > > > And Gene did reply: > >> Thinking aloud... > >> > >> I have been playing with an MA860H stepper drive which seems to work > >> well enough for my mill. > >> http://wallacecompany.com/ma860h/ > >> http://www.wallacecompany.com/machine_shop/Shizuoka/ > >> > >> I have an Antek toroidal transformer that is feeding 75 VAC to the > >> drive. The drive has an input limit of 80 VAC or 110 VDC. Although, > >> to feed three drives, I'll need a bigger transformer to supply 15 > >> Amps or more. I can use a 60Hz big iron transformer, but these are > >> big, heavy and expensive to purchase and ship. I could use multiple > >> toroids, but these are expensive. > >> > >> Then I got to thinking. What about a buck converter to convert mains > >> (120 or 240 VAC) to mains DC to high Hz AC to let's say 90 VDC? Or > >> more simply, pump the useful part of the mains AC into a large > >> capacitor in a way that maintains the DC voltage I need? This > >> sounds a little like an SCR circuit, such as a light dimmer, > >> universal motor speed controller, or SCR DC welder. This might be a > >> way to leverage a cheap second hand commodity device to a specialty > >> purpose. (But keeping in mind that common converters don't like > >> their outputs switched.) > >> > >> So, what are some ways of feeding roughly 90 VDC or 70 VAC at 15 > >> Amps to motor drives from 240 VAC mains? > > > > You might check your electronics junkbox, even if its located 35 > > miles away like mine is. There I managed to get an old phase linear > > dual 750 watt audio amp made back in the late 70's with one dead > > channel, gratis and made the supply for the spindle motor, a 1HP > > treadmill takeout out of it. With its output windings in parallel, > > I am getting around 110 volts rectified into some old 125 volt caps > > caught escaping from an old IBM pin pounder printer that weighed > > about 400 lbs. It contained a 25 amp rated bridge rectifier, and > > the whole thing weighs about 65 lbs once I'd packed it up into a box > > I could hang on the side of the cabinet under the z motor. Control > > now by a 5i25 tickling one of Jon Elsons servo drivers. > > > > Thats sweet, got rid of a bunch of ice cube relays I was using to > > reverse it, so not needing those makes it an economical solution. > > But I did have to outboard the fwd toroid with one wound from a > > gauge heavier wire to reduce the ohmic heating. The rest of it runs > > at room temps. I put a big heat sink on it but IMO it was a waste, > > it runs that cool. > > > > NBD except I got that toroid choke from alltronics & I think it was > > the last such one. So the next one wouldn't be for the tenner I got > > that one for. :( > > > > Cheers, Gene Heskett > > How about taking a 240 to 120 volt transformer (large control > transformer) with 15 amp windings on the low side (2KVA) and feed that > with 120 VAC on the high side. That will get you 60 VAC on the low > side. Get a buck/boost transformer and use that to boost the voltage > to the high side of the 240 to 120 volt transformer. You can > generally boost up to about 20% without a problem with a standard > buck/boost transformer. Now you have 60 VAC x 1.2 = 72 VAC. > > Most electrical surplus shops have 1+ KVA control transformers > gathering dust and you would still have full isolation. > > Dave
That would be ok for running bigger steppers, but would not get this 1hp up to more than 70% of its top speed at no load, with a corresponding loss of usable horsepower. That detail is of course moot on this rubber toy as it now has enough to hang the cutoff tool by bending the toolpost holder over about 1/4", bringing the spindle to a halt from 300 revs in about 10 degress of rotation. AKA a big wham. It springs back of course, but you will recall that I've accused that toy of having a rubber frame, severely limiting my depth of cut, enough times it qualifies for the chorus to my unlimited verse song. The whole carriage, from the H-frame up is made of wet spaghetti. Cast iron machinings can't possibly be that flexible, but they sure are. With the cnc doing x, I really have no use for the compound which is at least 75% of the problem, and when I find my round tuit again, I might machine a block to set on the crossfeed, offsetting the tool tip at least an inch to the right, which would then put the cutting forces a heck of a lot closer to straight down instead of hanging off the left side of the H by 3/4" or more, depending on what tool is in the QC post. Despite the way clamps/gibs, the right end of the H can be lifted off the bed far enough to stick a 10 thou feeler under it by a heavy cut. Did I mention its a toy, made out of rubber or cooked spaghetti yet? Oh, yeah.... That is why I am looking for a better lathe, something about 30" between centers and a spindle thru hole of around 1.75". If I should get super lucky and find both at a price and distance I can go get, the Z screw out of this lathe will become the Z screw for whatever mill I wind up with. 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> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ New Year. New Location. New Benefits. New Data Center in Ashburn, VA. GigeNET is offering a free month of service with a new server in Ashburn. Choose from 2 high performing configs, both with 100TB of bandwidth. Higher redundancy.Lower latency.Increased capacity.Completely compliant. http://p.sf.net/sfu/gigenet _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
