I would recommend against putting 240 VAC into a transformer winding originally designed for 120 VAC. While it would seem that a transformer is a simple ratio device, this assumption falls apart if the iron core cannot support the resulting magnetic flux density. Too little iron and it will saturate. When this happens the winding begins to approximate a very small resistance, almost a short circuit.
Using a transformer for voltages lower than rated is generally OK as is "running" them in "reverse". The ratio may prove to be slightly off because the manufacturer may have adjusted the stated ratio to compensate for the losses in the windings but this is typically only a few percent. Steve Stallings > -----Original Message----- > From: Kirk Wallace [mailto:kwall...@wallacecompany.com] > Sent: Wednesday, March 09, 2011 2:21 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Single Phase Lathe spindle motor question > > On Tue, 2011-03-08 at 18:52 -0800, Clint Washburn wrote: > > Are there any VFD's you recommend that would support such a motor? > > > > -----Original Message----- > > From: Kirk Wallace [mailto:kwall...@wallacecompany.com] > > Sent: Tuesday, March 08, 2011 12:00 AM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] Single Phase Lathe spindle motor question > > > > On Mon, 2011-03-07 at 22:03 -0800, Clint Washburn wrote: > > > I am in the process of converting my 1978 Hitachi Seiki > CNC lathe to EMC. > > > It currently has a 7.5 KW dc motor that used to be > powered by FUJI > > > SCR > ... snip > > It might be hard to find a VFD rated higher than a few HP > that can run on 240VAC input. > http://www.automationdirect.com/adc/Overview/Catalog/Drives/GS > 2_%28115_-z-_230_-z-_460_-z-_575_VAC_V-z-Hz_Control%29 > Short URL: http://alturl.com/qhdpo > > The higher HP drives seem to need 460VAC. I bought a VFD from > eBay and forgot to check the input voltage. It turned out to > be a 460VAC unit. I have a left over 240 to 120 transformer > that I now have 240 feeding the 120 end, and get 480 out the > other. The VFD works fine on this, but the transformer is > quite a bit bigger and heavier than the VFD. My guess is that > if you scan eBay for a 10 HP VFD that you will only find > units that need 460VAC. A transformer could fix this, but it > would need to be big and probably expensive. 10 HP would need > around 35Amps at 240 so keep this in mind too. I suppose a > 40Amp dryer outlet would work. You will most likely need a > mains filter too. > > I kind of like Jon's idea of trying to keep the DC motor. I > was thinking a golf cart driver might work, but I think the > output voltage will be too low. Maybe an EV controller? > http://www.evsource.com/tls_controllers.php > > These seem too expensive though. Maybe AC is the way to go. > > -- > Kirk Wallace > http://www.wallacecompany.com/machine_shop/ > http://www.wallacecompany.com/E45/index.html > California, USA > > > -------------------------------------------------------------- > ---------------- > Colocation vs. Managed Hosting > A question and answer guide to determining the best fit > for your organization - today and in the future. > http://p.sf.net/sfu/internap-sfd2d > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
