Peter Do I understand this correctly. One can rectify the mains with a bridge and then chop the voltage with a fet turning it off when the cap is charged to a level. The fet is in series with the load. The fet is turned on during every zero crossing. What happens when the fet turns of is there any precaution to be made?
------ Original Message ------ From: "Peter C. Wallace" <[email protected]> To: "Enhanced Machine Controller (EMC)" <[email protected]> Sent: 2015-01-24 19:19:01 Subject: Re: [Emc-users] DC Supply >On Sat, 24 Jan 2015, Kirk Wallace wrote: > >> Date: Sat, 24 Jan 2015 08:49:20 -0800 >> From: Kirk Wallace <[email protected]> >> Reply-To: "Enhanced Machine Controller (EMC)" >> <[email protected]> >> To: "Enhanced Machine Controller (EMC)" >><[email protected]> >> Subject: [Emc-users] DC Supply >> >> 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? >> >> -- >> Kirk Wallace >> http://www.wallacecompany.com/machine_shop/ >> http://www.wallacecompany.com/E45/ > > >A SCR controller should work, _but_ it will have trouble with a >capacitor >input filter because of the fast rise time when the SCR turns on. This >will >cause very large current spike charging the filter capacitors. A >solution >woudld be to use a inductor input filter but unfortunately the rather >large >filter inductor requied will be expensive > > >Using a single MOSFET, you could reverse the timing and do phase >control on >the rectified DC by turning the MOSFET on at zero crossings and off >when the >120Hz pulsating DC has reached the proper voltage. > >> >> >>------------------------------------------------------------------------------ >> 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 >> > >Peter Wallace >Mesa Electronics > >(\__/) >(='.'=) This is Bunny. Copy and paste bunny into your >(")_(") signature to help him gain world domination. > > >------------------------------------------------------------------------------ >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 ------------------------------------------------------------------------------ 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
