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 --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com ------------------------------------------------------------------------------ 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
