Question for Big Radial Arm Saw Owners

[Keith Avery]

I have 16" Delta RAS that has been rehabilitated but it is 3 phase and I haven't gotten power to it yet. It is a 5hp model. My question is if I use a static phase converter will I miss it only having 3 or so hp? I would rarely if ever cut anything over 4 inches. I am thinking the largest load would likely be a dado blade. My current dado only has a 5/8 arbor so I will have to buy either a 10 or 12 inch with 1 inch arbor for the RAS. I bought a Forrest Workers I 16" blade a few months back when Amazon was clearing them out, so I will normally use that blade(I also have a 16" Hi-ATB for plywood and melamine. I am just a hobbyist so if I have to pull a little slower for the cut it won't matter to much.
Second question. The saws motor is 13a if I remember right. I have seen a 4hp/13a VFD on ebay for about $225, would that be a better option? It says it can sustain 150 percent power for up to 1 minute. I doubt I would ever need a sustained 5hp for it. Electrical is not my area of strength, although I have read at least 100 threads about Rotary phase converters and know they would be the best but the extra wiring and converter would probably cost a grand. Opinions please. Thank you.

[Joe Jensen]

I am not an expert, but I do have a degree in electrical engineering (26 years ago ugg) and I read a ton before I put a VFD on my jointer. Here is what I know.
1) 3 phase motors are supposed to run smoother than single phase. I have three machines now with 3 phase motors and I do agree they run smoother than single phase.
2) When using a static converter don't really run as a 3 phase motor, that's why you get less power. I don't know if this means it runs less smoothly but I suspect so. A simple way of thinking about this would be to see a 3 phase motor as having a power nudge every 1/3rd rotation. If the static converter is not enabling all 3 phases, the nudges won't all happen.
3) Rotary is better than static but not as good as a VFD or real 3 phase. Rotary is a lot like a static, but they can start bigger loads and if you need a big converter they are a lot cheaper, the cheapest way to go.
4) VFDs make real 3 phase, but it's not very clean 3 phase power. Instead of a smooth sine wave they have little pulses that look like a bar graph trying to look like a smooth wave form. They are pretty expensive if you need more than 3HP. My jointer has a 3.8HP motor so I thought I needed a 5HP VFD. I called a manufacturer and the engineers there said for a motor that has a low startup load, and one that is unlikely to be heavily loaded, doesn't need a full load rated VFD. The one I bought was a TECO FM50. Also, it is rated for 50% overload, and can run that way for up to one minute. It also self protects, so supposedly you can't hurt it.
5) Digital phase converters. These are bigger than VFDs and not variable speed controllable. They are supposed to make better 3 phase than real line 3 phase from the utility.

If would buy a Teco again. If you find one that is rated to self protect and handle up to 50% overload I think you would be ok with a 3HP one. the one I bought was an upgraded totally sealed one and I paid $315 a few years ago. A normal case version was like $250.

[Mike Heidrick]

I own your exact RAS in 3hp single phase. It is perfect and takes a complete 10" Ridge carbide Dado stack perfectly. it is a beast.

[david brum]

Hi Keith. For what it's worth, I have a Dewalt MBF radial saw which has .75hp and runs a 10" blade just fine. I've crosscut 3" hardwood, no problem. I would imagine that 3hp would cut through anything that will fit into that saw, given that it it properly aligned and tuned. Of course, if you are actually ripping with that RAS, that could be a different story.

I don't know much about phase converters either, except that my Jet lathe has a VDF and it doesn't seem at all fragile. I think the best argument for a rotary converter is if you plan to have multiple 3 phase machines. For a solitary 3 phase machine, the VDF is the way I'd go.

[Dave Cav]

I have 16" Delta RAS that has been rehabilitated but it is 3 phase and I haven't gotten power to it yet. It is a 5hp model. My question is if I use a static phase converter will I miss it only having 3 or so hp? I would rarely if ever cut anything over 4 inches. I am thinking the largest load would likely be a dado blade. My current dado only has a 5/8 arbor so I will have to buy either a 10 or 12 inch with 1 inch arbor for the RAS. I bought a Forrest Workers I 16" blade a few months back when Amazon was clearing them out, so I will normally use that blade(I also have a 16" Hi-ATB for plywood and melamine. I am just a hobbyist so if I have to pull a little slower for the cut it won't matter to much.
Second question. The saws motor is 13a if I remember right. I have seen a 4hp/13a VFD on ebay for about $225, would that be a better option? It says it can sustain 150 percent power for up to 1 minute. I doubt I would ever need a sustained 5hp for it. Electrical is not my area of strength, although I have read at least 100 threads about Rotary phase converters and know they would be the best but the extra wiring and converter would probably cost a grand. Opinions please. Thank you.

Generally VFDs are rated by amperage at rated voltage and the HP rating is just kind of an estimate. When in doubt, it's always safest to go with the amp rating.

I have seen the VFDs you are referring to on Ebay. They are shipped direct from mainland China and so they bypass a US vendor that may be able to provide tech support if needed. I haven't ever used one of these particular VFDs, and would be a little leary of them due to the lack of US based support.

I am running two 5 HP, 3 phase machines on single phase VFDs. One is a Powermatic 180 thickness planer, the other is a Delta 12/14" table saw. I am using a TECO 7300CV 7.5 HP VFD to run the thickness planer, and a TECO FM50 3 HP VFD to run the table saw. I am using a smaller than rated VFD for the table saw because it's my belief that the saw will only pull full load amps when cutting very heavy stock with a 14" blade, and I rarely cut anything over 6/4, and always use a 12" blade, so I don't think I'm even approaching full load amps on the table saw. I also have the saw set up for a 10 second spin up time and on start up it never draws even half the rated amperage.

I'm using a larger VFD on the thickness planer to handle both the higher starting torque (a thickness planer has a lot more stuff to get moving than a table saw) and I am usually running it close to full load most of the time. Since you could get this planer with a 5, 7.5 or 10 HP motor, it would be very easy to overload the motor with too big a cut. Also, the 7300CV is nominally a "3 phase in/3 phase out" VFD; however, you can run it single phase in, 3 phase out if you go to a larger size. The 7300CV also has a lot more features than the basic FM50. One is I can configure the readout to show actual amp draw during operation. That way I can fine tune my feed speed and cut depth for max amps without going over the motor rating (for very long, anyway).

I think your 16" RAS should work OK on a 3 HP VFD as I am running my table saw, if all you plan to do is normal cabinet work. However, if you plan to crosscut heavy timbers all day using the full capacity of the saw, then you will probably need a heavier VFD. In either case, don't forget you will need an adequate 2 pole 220 single phase breaker to feed the vfd. I'm running my thickness planer off of a 60 amp breaker.

PM me if you need additional info.

[Larry Edgerton]

I ran my OMGA 5hp/3ph on a static converter for a couple of years and it was not an issue. I am running on a 50hp rotary converter now and see no difference. I hope to get one of the newer electronic converters [not a VFD] that will run a whole shop, but the money is not there just yet.