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3 Phase Equipment in my Single Phase Shop

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Forum topic by DylanC posted 02-02-2011 04:02 AM 5253 views 0 times favorited 21 replies Add to Favorites Watch
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DylanC

196 posts in 2134 days


02-02-2011 04:02 AM

[NOTE]: Just in case anyone reads my blog, a similar post appears there.

I just replaced a PoS Craftsman benchtop/portable table saw with a Delta 34-806 Unisaw (5 HP, 3 Phase motor). I planned on powering the saw with a medium-duty 5 HP static phase converter from Enco (www.use-enco.com) for ~$120. So, I bought the saw and ordered the phase converter.

Today, I called Enco technical support after receiving an e-mail that basically stated all customers purchasing phase converters need to consult with technical support about the application. After explaining that I would be starting the motor under very light loads (just the pulleys and the blade) and that the motor would almost never be loaded to the full 5 HP (typically 3 or less), I was told that the medium duty phase converter was basically capable of starting and running an unloaded 5 HP motor. Under almost any other circumstances they recommend their “heavy-duty” phase converters. For my 5 HP motor the cost would go up to just under $200.

Hmm…not great news. I knew that running this saw with a static phase converter was kind of a cobble-job to begin with, but for $120 it was much more attractive than a $300 replacement motor, a $600 VFD, or an $800 rotary phase converter. Now, I’m not so sure.

So, I’m back to square one, except that I now own an unusable Unisaw. I am currently looking into three options, all around $300 or less.

Option #1: Purchase the “Heavy-Duty” Static Phase Converter
Option #2: Replace the motor with a 3 HP single phase unit. Probably just over $300 by the time I replace the start-stop control and the drive pulley.
Option #3: Use an undersized 3 HP VFD as a phase converter. I know that 5 HP, Single Phase Input VFDs are available, but they’re much less common and more expensive than a 3 HP version. I’ve got a technical inquiry in with one of the vendors to see if this is a valid option.

Each option has its advantages and disadvantages. I suppose I could also build a phase converter, but I’m not really keen on having a 10HP idler motor sitting in my shop. That and it would probably be just as expensive as replacing the motor. My “perfect” solution? Find a working, used 5 HP Single Phase Input VFD for ~$100-$200. Odds of finding one: zero or close to it.

I’d appreciate anyone’s input on any of my options, or one I haven’t considered. The worst part? Explaining to my wife that this project is going over budget.

-DylanC

-- Dylan C ...Seems like all ever I make is sawdust...


21 replies so far

View GaryK's profile

GaryK

10262 posts in 3448 days


#1 posted 02-02-2011 04:14 AM

Do you really think you need 5HP? My Unisaw has a 3HP 220V Single phase and it has cut, to full depth of the blade, everything I have thrown at it. Maple, purpleheart, wenge…

A 3HP motor would be cheaper.

It’s a straight forward solution that is sure to work without a doubt.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View Todd A. Clippinger's profile

Todd A. Clippinger

8901 posts in 3559 days


#2 posted 02-02-2011 04:25 AM

I am with GaryK and my experience is the same.

Just get it over with, it will last forever. When you break the price down year after year it works out to be fairly economical.

-- Todd A. Clippinger, Montana, http://americancraftsmanworkshop.com

View Loren's profile

Loren

8295 posts in 3108 days


#3 posted 02-02-2011 04:30 AM

You’ll be in a position to acquire other 3-phase equipment (at rock
bottom prices because 99% of the home shop guys will not bid in
auctions and walk away from good deals on such machines) if you
bite the bullet and set up for 3-phase now.

I’ve never gone 3-phase (had a false start once) but I’ve seen many
tempting deals on all manner of heavy 3-phase equipment at scrap
metal prices. Lathes, pin routers, planers, mills, etc.

View cabmaker's profile (online now)

cabmaker

1506 posts in 2269 days


#4 posted 02-02-2011 04:38 AM

Static convertors are not happy with lots of cycling. The guy was telling you right about needing the next one up. I would recomend biting the bullet and replace with a single phase motor. When you try to put to many links into the equasion that begats other problems. So based on my personal experiances, unless you have three phase service you should swap motors. Good luck ! JB

View Carl Webster's profile

Carl Webster

82 posts in 2258 days


#5 posted 02-02-2011 05:01 AM

Installing 3 phase power for a Hobby Shop is very expensive and highly impractical. You will end up with high power bills for a low usage.

-- Carl in SC

View Vrtigo1's profile

Vrtigo1

434 posts in 2451 days


#6 posted 02-02-2011 05:03 AM

Option #4 – get your shop set up for 3 phase power, as Loren said. I have no knowledge of 3 phase so don’t have any idea what that might cost. I know my house has two hot lines coming in from the pole outside, and you get 220V when you combine them, and I think that would be two phase? If that’s so, then it seems like it’d be a pretty big deal to get a third phase brought in, but again I don’t know anything about it.

If I’m reading your question correctly, the cost difference between the converter you originally spec’d and the one they’re recommending is $80. If you just bought a 5 HP Unisaw, then I’m gonna go out on a limb and say that $80 probably isn’t gonna make a huge difference in your overall project budget.

View DylanC's profile

DylanC

196 posts in 2134 days


#7 posted 02-02-2011 05:09 AM

GaryK said:
Do you really think you need 5HP?

No, but thats what it has now. If I replace the motor it will be with a 3 HP single phase unit. Cost: $290 from Grizzly, $480 from sawcenter.com. I would also have to factor in costs for new start/stop control and possibly overload protection. It gets costly quick.

Loren Said:
You’ll be in a position to acquire other 3-phase equipment (at rock
bottom prices because 99% of the home shop guys will not bid in
auctions and walk away from good deals on such machines) if you
bite the bullet and set up for 3-phase now.

I agree with the concept (thats why I got the Unisaw for such a bargain), but I don’t think its that easy. Most 3-phase equipment is at least 5 HP, usually 7.5 or 10 and up. In order to “set-up for three phase” for, say, 10 HP, I’d need to shell out between $800 and $1200. Considering this is a novice hobbyist’s shop, thats a pretty tough sell. Bottom line: I’m approaching this problem as a single-machine solution with no future plans to buy 3 phase equipment. On the other hand, if the undersized VFD solution works out, I could run any 3 phase 3-5 HP lathe/Mill, etc. with just over $300 invested. That is a good argument for going that route.

-- Dylan C ...Seems like all ever I make is sawdust...

View Scsmith42's profile

Scsmith42

125 posts in 2137 days


#8 posted 02-02-2011 05:29 AM

I’ve operated 3 phase equipment off of rotary phase converters (RPC) in my previous shop, and do the same in my existing shop. In my instance, I installed a 3 phase load center, and fed it from a 30 hp rotary phase converter. All of my 3-phase equipment was then wired to the load center.

It works great. You do not need to buy a brand new RPC, they come up frequently on craigslist and also e-bay. There is not much to wear out on them either. Here is a used 10 hp RPC on e-bay for 675.00

http://cgi.ebay.com/Rotary-3-phase-converter-runs-up-10-HP-equipment-/250764543683?pt=BI_Electrical_Equipment_Tools&hash=item3a62bb46c3

I also have a 5 hp 12” cabinet saw, and am glad that I have the extra power (my last saw was 3 hp).

If you invest in the RPC, you have a tool that will enable you to purchase future 3 phase equipment.

-- Scott, North Carolina, www.quartersawnoak.com

View GaryK's profile

GaryK

10262 posts in 3448 days


#9 posted 02-02-2011 06:04 AM

I have a 2HP 3PH vertical mill that I use a static converter on. Been using it for 20+ years. I don’t use it that often though.

At the time I chose 3PH because I was unaware that you could reverse direction with single phase on the fly.

-- Gary - Never pass up the opportunity to make a mistake look like you planned it that way - Tyler, TX

View TopamaxSurvivor's profile

TopamaxSurvivor

17654 posts in 3136 days


#10 posted 02-02-2011 02:15 PM

One other option since you are looking at used VFDs. Get a 3 phase VFD, feed it with single phase power. You will need to over size it by about a 3rd. If you find a 7.5 hp for the 5 hp motor, you should be in fine shape.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View DylanC's profile

DylanC

196 posts in 2134 days


#11 posted 02-03-2011 03:35 AM

I got a response to my technical inquiry about using an udersized VFD to power my tablesaw. I’ve included the complete response below but the bottom line is that the manufacturer does not recommend this type of installation because the results are a bit unpredictable. I’m not really keen on shelling out 300+ dollars for unpredictable results. So far the leading option is the heavy-duty static phase converter.

-DylanC

——————————————
Dear Dylan,

Thank you for your inquiry.

The GS2-23P0 would have a maximum rated output current of 10A. In the
drive, parameter P0.01 is the motor nameplate amps – and also is for
overload protection of the motor. The range of this parameter is from 0.3
to 1.0 of the drive rated current, in the case of the GS2-23P0 – from 3 to
10 A.

The real issue is that you have a 3HP drive on a 5HP motor. The drive is
undersized for this application – so, it’s hard to predict how well this
will work. If you require a 5HP for your load / torque requirements, then
using a 3HP drive might not be sufficient. Limiting the 5HP motor to a 3HP
current does not necessarily mean that you will get 3HP of torque out of
the motor.

If at all possible, I would recommend movign to the GS2-25P0; howver, that
does require 3 phase input power.

I hope this is helpful in answering your questions. If I can be of further
assistance, please feel free to contact me.

Kind Regards,
——————————————
Billy Sonnenthal
Technical Support Team
AutomationDirect.com

-- Dylan C ...Seems like all ever I make is sawdust...

View TopamaxSurvivor's profile

TopamaxSurvivor

17654 posts in 3136 days


#12 posted 02-03-2011 03:43 AM

If your motor is not “drive rated” you also run the risk of it just tripping the drive out on ground fault protection. If the money is close to the same, I would opt for a 3 or 5 hp 240 single phase motor and be happy ever after :-))

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View DylanC's profile

DylanC

196 posts in 2134 days


#13 posted 02-03-2011 04:45 AM

TopamaxSurvivor Said
Get a 3 phase VFD, feed it with single phase power. You will need to over size it by about a 3rd. If you find a 7.5 hp for the 5 hp motor, you should be in fine shape.

Have you seen this done? I’ve read one other story about someting like this, but I’d like to get some more reliable information.

-- Dylan C ...Seems like all ever I make is sawdust...

View ChunkyC's profile

ChunkyC

856 posts in 2714 days


#14 posted 02-03-2011 05:26 AM

Dylan: My DP is done this way. 3 HP motor with an Allen Bradley 1p → 3p drive. This can be done but you loose power. I converted mine to 3p w/ a vfd so that I can easily change the speed. No more moving belts for this EE!

I purchased a 1800 RPM motor (minus the slip) and I can change the freq from 0 – 120 hz (0-3600 RPM).

-- Chunk's Workshop pictures: http://spadfest.rcspads.com/thumbnails.php?album=135

View DylanC's profile

DylanC

196 posts in 2134 days


#15 posted 02-03-2011 06:45 AM

I’ve just spent a few hours reading various accounts of using VFDs for 3-phase power conversion. What I’ve been able to determine is that most major manufacturers only offer this functionality on motors up to 3 HP. There are one or two off-brand chinese units (selling on eBay) that go as high as 5 HP, but I didn’t really get a good feeling about the quality of the unit or the availability of customer support. There are several accounts of people who use oversized (approximately 2x) VFDs for this purpose, albeit unsupported by the manufacturer. This isn’t really an option for me because I don’y want to spend $600+ on a VFD. For that price I could get a rotary phase converter.

So this is how my options are looking:
Option #1: Purchase the “Heavy-Duty” Static Phase Converter
Not the optimal solution, but the most cost effective and I’ve read and heard of many people who’ve used these without issue. Derates my motor to ~3 HP, but thats not a concern. Also gives me the added benefit of being able to run other 3-phase equipment in the future.

Option #2: Replace the motor with a 3 HP single phase unit.
A good solution, but expensive. Main disadvantage is that the cost is higher than the static phase converter and will not give me the option of using additional 3-phase tools in the future.

Option #3: Use an undersized 3 HP VFD.
I still think this setup has a good chance of success. If I had a 3 HP vfd (or even 5 or 10) just laying around, I’d try it. But I’m not willing to gamble with my money like that. Maybe I’ll look around and see if anyone local has one that I can “try before I buy,” but I’d rather make a decision quickly and get the saw up and running.

My guess is I’ll make a final determination by Monday.

-DylanC

-- Dylan C ...Seems like all ever I make is sawdust...

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