Delta Unisaw

[Kent E. Matthew]

I may have a line on a Uni off of Craigslist for 400. He has a three phase motor on it. I don't have three phase power, but I do have 220 single phase. The price is really right. Is there anything I can do to get this saw to work on single phase? What would I need to make it run on three phase at my house?

[Paul Libby]

Kent, you can either get a phase converter or put a single phase motor in it. Do a word search on three phase and you will find that this has been discussed in great detail a number of times. There is great information in the previous discussions.

[M Toupin]

Kent,
You have basically 4 options:
static converter
rotary phase converter
Variable Frequency Drive (VFD)
replace the motor with a single phase motor

A off the shelf replacement single phase motor may or may not be variable. Depending on the age of the machine this can get very expensive, very fast if you want to stay original.

A static converter is basically just a way to start a 3ph motor and run it on single phase. The drawback is you loose about 1/3 the power.

this leaves you VFD and RPC. If this is the only 3ph machine you own or plan to own then a VFD is very cost effective. A 2hp version from Factorymation will run you about $145. Check out the FM50 model which will run a uni just fine. Another up side is the VFD can be bolted directly to the machine and it becomes one unit.

A RPC can either be shop built or purchased and produces 3ph much like a generator. A RPC is generally more expensive up front (unless you have all the parts on hand and build your own). The pay off is if you plan to have a whole shop full of 3ph equipment then the cost over individual VFDs for each machine quickly tips in the favor of the RPC. The down side is you have to also consider a 3ph power distribution system.

You'll have to decide what's best for your current/future needs. Personally, if it was me, and the uni was the only 3ph machine I had, I'd opt for the VFD which would be a lot cheaper than a new single phase motor.

Mike

[Kent E. Matthew]

Your suggestions are interesting. I have located and looked at the FM50. This part would take the place of the On/Off switch? Wiring would have to be pretty simple for me to even consider this option.

[Rick Christopherson]

Yes, the wiring is simple. You bypass the saw's internal On/Off switch, and wire the 3 motor leads directly to the VFD.

If you wanted to get fancy, you could reuse the saw's On/Off switches to remotely operate the VFD. The VFD's manual would even give you wiring diagrams for how to do this.

Remember that for larger motors, you need to oversize the VFD if it does not support single-phase input. That is, if the motor is 3 hp, but the 3 hp VFD states that it needs 3-phase power, then you would need a 5-hp VFD.

[M Toupin]

FVDs don't like being turned on/off with a load attached so you need a power switch for the VFD to turn it on. The saw is then started/stopped using the start/stop function on the VFD. The VFD is normally left powered up during the work session.

As Rick said, you could use the existing switch on the saw for one of the functions, either powering up the VFD or as the Start/stop function for the saw. The VFD only needs a open/closed switch to actually control the motor so you can get as fancy as you want.

There are lots of VFD makes and models with all sorts of fancy functions. For a TS you only need 3ph output so you really don't need all the fancy functions which drive up the cost. The FM50 is a bare bones model and comes in models up to 3hp with single phase 220v input. No matter what make/model you choose it's not difficult to wire if you have a basic understanding of electricity. If you can wire a lamp you can install a VFD. It's really that simple, 2 wires in, 3 wires out to the motor. The nice part of 3ph is you can't screw up and hurt anything wiring the 3 legs of the 3ph side. Worst case is your motor will run backward which can be corrected by reversing any two of your 3ph legs.

Good luck

Mike

[Jack Clay]

If the saw was in good shape as far as rust and cast iron parts, the bearings, depending on what year, and what fence it has that would be a good price. I have been looking for awhile now for an older Unisaw and had no luck yet. What I have found is 80’s to 90’s models with a good fence and in good shape for 850 to 1000 dollars on Crag in my area. If you get the model number you can find how old it is. You can buy a 3 or 4 hp direct replacement motor for 280 to 340 dollars shipped. With other upgrades you are still way below 1000 dollars. Good lucks I hope this helps.