On Tuesday 17 October 2006 4:02 pm, PicDude wrote: > Hi all, > > I am looking at purchasing a large-ish CNC mill, but these generally > require 220VAC 3-phase, though some require 220VAC 1-phase. At the same > time, I'm also looking into renting an apartment, but finding an attached > garage (so I can get 220V from the panel or dryer outlet in the garage) > seems to be iffy. Detached garages only have 110V, and I'm not sure if this > will be a show-stopper. This is in the USA, btw. > > First, 220V 3-phase is not a problem to get from 220V 1-phase, using a > phase converter. But 220V 1-phase seems to be a problem... here is a link about this topic.. and how to build one.. http://www.metalwebnews.com/howto/ph-conv/ph-conv.html > > If I get 220V from a dryer outlet, I understand that there are grounding > differences (dryer outlets are grounded to neutral?) that could be a > show-stopper in using the mill, which expect to be grounded to earth. Is > there a fix for this? First off NEC allows two different configurations. 3 wire and 4 wire. so 3 wire is L1, L2, Ground 4 wire is L1,L2,Ground, Neutral. you can get 220 accross L1, L2 without using either ground or neutral. ground is for safety. neutral is for splitting phases into 110v.. This change was put into NEC because some stoves/dryers have 110v components. and they were using ground to power them.. Grounds and neutrals are ONLY allowed to be tied together at the source.. ie the supply panel.. > > If I get 220V from a breaker panel, is it the same as the dryer outlet? Or > would I be able to get properly-grounded 220V there? YES.. that is where it comes from.. > > If I use the 110V outlet, I can step that up using a transformer, but I'm > limited to 15A. That would be ~7A or less at 220V, factoring in > transformer inefficiency. And the mill's spindle motor needs more than > that. However, I'm wondering why the power outlet is limited to 15A? Is > it because of the wiring? If there are multiple outlets in the garage, and > each is rated to 15A, then I should be able to find the "first" outlet in > the garage (where the supply wires come into the garage) and wire up a > beefier outlet at that point. The wiring up to that point should be able > to handle more current -- theoretically 15A x Num_Outlets. Is this > correct? I'd also need to change the breaker for this circuit. No this is not correct.. the breaker is sized in order to trip on the lowest common demonator.. ie wiring size, plug capacity etc.. So the most you can get from a 15A branch is 15A doesn't matter if you have 1000 plugs on the branch. I think the easiest answer to the problem is to change the CNC's motor to a proper single phase 220 volt.. Fred > > I don't mind getting an electrician in there to add an outlet and run some > lines from the breaker panel, etc, but I can't get them to run larger lines > into the garage without raising some eyebrows. > > Cheers, > -Neil. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist