Pwk5017 Posted March 15, 2015 Report Share Posted March 15, 2015 I'm looking at a used 5hp Rockwell unisaw. This guy is the second owner of the saw and has a VFD on it. I believe the age of the saw is roughly 20-25 years old. It has a unifence, not a bies. I know nothing about phase conversion, but I'm skeptical of buying 3 phase machines that run off phase converters. IVe read they lose power and life under conversion. I'm currently using a contractor saw and would love more power and a bigger work surface. What would you offer for a saw that looks to be in decent shape, but was in a production environment at some point? Also, what are the downsides to running a 3phase machine on a convertor in a single phase residence? Quote Link to comment Share on other sites More sharing options...
wdwerker Posted March 16, 2015 Report Share Posted March 16, 2015 I have a 5 hp single,phase Unisaw that was formerly in a commercial production shop , it's at least 25 years old. Still works great. I have no,knowledge about 3 phase or converters. Mine has a Biesmeyer fence . Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted March 16, 2015 Report Share Posted March 16, 2015 The VFD should only be used to produce 3 phases from 1, not to vary the motor speed. It is true that using a VFD with a motor not designed for VFD operation can reduce the life of the motor, but running a single speed, and with typical TS operation, I expect it will last a long time. Beware that you won't achieve the full 5hp, as there is some inefficiency in the phase conversion. As for coming out of a production shop, I'd examine it closely for worn out bearings. If the price is right, it should be a good saw. Quote Link to comment Share on other sites More sharing options...
dcustoms Posted March 16, 2015 Report Share Posted March 16, 2015 The best type of phase converter is a rotary phase converter. I run my 4hp Coral Spray booth off of one been running strong for 5 years now. A static phase converter would not be good for a table saw due to the large amount of heat that builds up, static phase converters are for short cycle machines... think a radial arm saw running for minutes at a time. A rotary phase converter works much better and allows for indefinite run times. They are however an investment but could be wired to allow for other 3phase machines in the future. Quote Link to comment Share on other sites More sharing options...
Coastyboy Posted March 17, 2015 Report Share Posted March 17, 2015 I ran an old Northfield shaper (3 or 5hp ?) with a static phase converter, never saw any problems, although I never pushed it to it's limit either by running it all day long. There are many plans to build your own phase convertors on line, might be worth looking at Quote Link to comment Share on other sites More sharing options...
Coastyboy Posted March 17, 2015 Report Share Posted March 17, 2015 Zoro has a 2-6 hp range rotary one for 612.00, thats a lot to add to the price of a used saw Quote Link to comment Share on other sites More sharing options...
Coastyboy Posted March 17, 2015 Report Share Posted March 17, 2015 here is something to read about phase converters, http://www.3phasepower.org/staticphaseconverters.htm Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted March 17, 2015 Report Share Posted March 17, 2015 For a single machine, you are probably better off to just replace the motor, if the VFD isn't doing the job for you. Rotary converters can be quite an investment. Quote Link to comment Share on other sites More sharing options...
Coastyboy Posted March 17, 2015 Report Share Posted March 17, 2015 agreed Quote Link to comment Share on other sites More sharing options...
andrew-in-austin Posted March 18, 2015 Report Share Posted March 18, 2015 There are tons of people using VFDs with zero problems. I would not worry about the VFD part. More of a concern would be the lack of riving knife and bad dust collection. Quote Link to comment Share on other sites More sharing options...
minorhero Posted March 18, 2015 Report Share Posted March 18, 2015 I own several 3phase machines running on a few different vfd. That said, I would bet good money that this saw is either a) not 5hp or not running on vfd. While it is relatively common to see vfd at 3hp or less, its pretty rare to see them on more then 3hp machines. Likely you are looking at a static phase converter or a rotarty. If the latter, that would be awesome to get. If the former, it would be much less awesome. Quote Link to comment Share on other sites More sharing options...
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