Setting Up Shop #1: 3 Phase Power in a Home Workshop

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Blog entry by DylanC posted 02-02-2011 03:41 AM 5883 reads 0 times favorited 0 comments Add to Favorites Watch
no previous part Part 1 of Setting Up Shop series Part 2: Three Phase Power...My Way »

I just replaced a PoS Craftsman benchtop/portable table saw with a Delta 34-806 Unisaw. The problem? The unisaw has a 5 HP, 3 Phase motor. My shop has only 220V, 50A electrical service. I know all of this before I bought the saw. “No problem,” I thought. “I’ll get a static phase converter, which will de-rate the motor by 30% and I’ll have the equivalent of a 3 HP Unisaw…Perfect.” I had already done alot of the gound work evaluating the cost and availability of rotary phase converters, VFDs, replacement motors, etc., and discovered that a medium-duty 5 HP static phase converter from Enco ( would run me ~$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 fully 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. 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.

The worst part? Explaining to my wife that this project is going over budget.

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

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