Surgo

Thanks, that does help. Table 430.250 says half of what I expected, which is that P=IV is the ratio here. The piece I was missing was what the drive itself would end up consuming, which I now see via your answer that I could simply read off the rated input current from the VFD. Well, in retrospect that was stupidly obvious :headbang:. And that's some serious efficiency loss on that drive! Not that I'd really expect anything different given the monstrous manipulations you have to do to single-phase input. I'll probably stick with the angle grinder and hand files and just wait to finish building my shop rather than temporarily purchase and use a 1/2 HP motor.

According to the very helpful VFD buying guide at https://www.vfds.com/blog/vfd-buying-guide, a rule of thumb is VFD size on single-phase power of 2x the full load amperage draw of the motor. Which, I suppose, answers my question exactly. So that's good information for anyone else facing the same dilemma I am. Though I'm not entirely clear on *how* that rule came around. EG, wouldn't we still have to multiply the amperage draw by 4 to get what would be taken in the 110v line? I'm not an electrician, I only have a basic understanding of electrical components.

Breaker box to outlet length is unknown right now (I might have the house's electrical diagram laying around somewhere...hopefully). I'm guessing that it's 14 gauge based on the shape of the outlet via this lovely diagram: https://fthmb.tqn.com/tMILNUH02SPqlR5U2C5EWWqWTlo=/960x0/filters:no_upscale()/1-outlets-56a4a2855f9b58b7d0d7eec5.jpg So I'd probably use wire from a 14 gauge extension cord to complete the wiring, which would add no more than 3 feet to the total length of the run.

Until I build a shop, I'm limited to a good old residential 110v, 15-amp-limit circuit. Yuck! Assuming I want to run a 3-phase motor with VFD, I'm trying to figure out the strongest motor I can run is. The question is proving...a bit complicated. Take this fairly basic motor for example: (This might be mislabeled, because the pl;ate on it says it's 2HP). The rated amperage is 2.69 at max frequency. Now if I go by P=IV then at 110v in, I'd be looking at 10.76 amps. But...there's no way it's that simple. The VFD is doing a more than just stepping the voltage up or down, so it could be drawing something larger and losing it through heat. And then there's inrush current to the motor consider; will a VFD cut that off or will that still go substantially higher than 15amp and trip the breaker? I guess what I'm really asking -- is there a page somewhere that breaks down how to calculate what the best you can handle on such a line is? I feel like there's no way a simple proportional P=IV calculation would be correct here because I know I shouldn't be able to run a 2hp motor on this line!

Thanks for the light bulb tip! I'd have never thought of that. I'll have to go dig out one of those old incandescent, hah. Also thanks for the tip on Plastix! Spending a lot less money to get something better is the best feeling in the world.

I understand that people generally cure satanite in their forges first by letting it air dry for a few hours, followed by cycles of firing the forge. My question is around that initial air dry. I'd like to put the forge together this winter. It'll be a standard wool + satanite + ITC-100 combination on the inside. However winters up here can get pretty cold, and this winter especially it's supposed to be a real whopper. There's no kind of heating where I'll be doing the forge (my garage). Given that it's likely going to remain below the freezing point for most of the winter, that air dry step won't be possible. Has anyone else had success skipping the air dry and immediately starting the firing cycles? Or have you found that air dry step to be essential? If it makes a difference, I suppose I'll be waiting for the spring to finish the forge.

Everyone's favorite 15 kW induction heater has gotten pretty well priced nowadays. Considering how much equipment like anvils cost right now, it's quite reasonable! The one thing about it that I dislike is having to make coils for oddly shaped workpieces. I found something interesting when I was searching; Ambrell for their induction heaters makes a flexible coil you can wrap around whatever you want. See here for details: http://www.forgingmagazine.com/heating/flexible-induction-coil Does anyone have any idea how they do that? I've seen some really long flexible coils used with Chinese air-cooled induction machines, but nothing for water cooling (is that even possible?). If such a thing was possible, didn't lose power compared to the fixed coil (Ambrell's doesn't seem to go that high in temperature) and I could buy or make one, an induction heater would be an instant buy for me.