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changing over a 3ph saw

2K views 34 replies 12 participants last post by  upinflames 
#1 · (Edited by Moderator)
hey guys,
If i were to buy a 3ph table saw, how easy is it to change over to a single phase saw, if I already have a single phase motor? Is it as easy as unbolting one motor and bolting in the new one, or is it more complicated than that?
 
#2 ·
If the motor mounts are the same, yes, it's just about that simple. You would need to change the switch also. If the wiring is good, just use two hots and the ground for 220 volts, or one hot, a neutral and ground for 110. . Make sure you use the same colors at each end…...... Jerry (in Tucson)
 
#5 · (Edited by Moderator)
Is it as easy as unbolting one motor and bolting in the new one
99% of the time, no. The frame (in particular, the size of the motor and the mounting plate) needs to be the same or you will have to do some modifications as to how you mount it. The shaft size needs to be the same if you want to use the old motor pulley, otherwise you will need to find a new pulley with the same outside diameter and the proper bore size for the new motor (or get a new arbor pulley to compensate). The speed (RPM) of the motor needs to be the same, or you might have to do some creative pulley swaps to get it back to spec (which may or may not even be possible). The rotation direction needs to be the same or the new motor will need to have the ability to reverse direction. The new motors HP needs to be roughly the same, or at least not exceeding the manufacturers max HP recommendation. The existing 3-phase starter most likely will also need to be replaced/modified to use for single phase, and the heaters usually will need to be replaced to match the new motor. Some starters can be used for both, some can't.

For most situations, it's usually easier (and cheaper) to just run it with the existing 3-phase motor… either with a VFD or a static phase converter. For larger (3hp+) motors, it becomes a crap shoot as you will need an RPC which may or may not be more expensive than a new motor. Also, a 3-phase motor is much more efficient and reliable, and if coupled with a VFD, can give you extra features not possible with a single phase one.

Cheers,
Brad
 
#6 ·
wow brad, thats a lot of info, thanks. the table saw that I am looking at is a PM66 the person selling it has the 3ph motor currently installed with a 1ph baldor motor that he is including with the table saw. I guess I will have a few questions to ask him, thanks
-Ryan
 
#7 · (Edited by Moderator)
Unless the Baldor is a significant upgrade in HP and as long as the existing motor is 3HP or less, tell them to keep the Baldor and knock $100 off the price. You can pick up a VFD for that motor for under $200, and can sell the 3 phase starter (not needed with a VFD) to make up the difference.

Cheers,
Brad
 
#8 ·
Unless the Baldor is a significant upgrade in HP and as long as the existing motor is 3HP or less, tell them to keep the Baldor and knock $100 off the price. You can pick up a VFD for that motor for under $200, and can sell the 3 phase starter (not needed with a VFD) to make up the difference.

Cheers,
Brad

- MrUnix
+1 on what he said!
 
#10 ·
ok a little more info…
both motors are 5HP and have the same size shaft, and both spin the same way, is it worth the buy

- Duffman
Like MrUnix mentioned, anything over 3hp can't be used with a VFD, so I would say go with it. Tell him to knock some money off and keep the 3ph stuff. Or buy it all, change it over to 1ph and sell the surplus motor/starter. Can't say that I've ever seen a 5hp motor in 1ph for a saw…. that's gotta be a pretty big motor.
 
#11 · (Edited by Moderator)
...Can t say that I ve ever seen a 5hp motor in 1ph for a saw…. that s gotta be a pretty big motor.

- 01ntrain
Powermatic has made 5hp 1ph saws for a while, you can currently get them in the PM2000 model, I believe they are about $3700 or so with 30in rails. SawStop makes one as well for around $4300.
 
#14 ·
Sounds like you might get lucky and the motor was obtained specifically to replace the 3-phase one, but never installed. If the mount is the same, then all you would need to worry about is the electrics, which would be much cheaper than trying to find an RPC for it.

Cheers,
Brad
 
#19 ·
$525 for a PM66 with a new 5hp single phase baldor motor???! You realize that motor is more than $500, right? Your used 3 phase equipment is about $200ish to the right buyer. GO BUY THAT SAW BEFORE I DRIVE 2 HOURS TO BUY IT BEFORE YOU. a single phase PM66 in good shape would sell for $1000 easy peasy.
 
#23 ·
Make sure the replacement motor has the same frame. The PM 66 motor has a c face for mounting, hence the 145TC frame, the shaft would be 7/8". The biggest problem with most deals like this is that the replacement motor they found at the salvage yard ain't gonna work.
The saw would still be a good deal, you can get a 3hp replacement for around $350.00…
 
#25 ·
If it's the same diameter shaft, you may be able to cobble something up to hold it. Certainly it's possible, but may not be feasible depending on the specifics of the motor mount, the pulley and belt locations, and the clearances around the motor mount.
 
#26 ·
If the new motor is included in the deal, get it, the face of the motor is the "c "part, that is how it is mounted to the saw. I've never seen anyone "cobble" a c mount, not that it hasn't been attempted, in other words, a unisaw or compressor motor normally will not have the c face for mounting.

http://www.baldor.com/Shared/pdf/nema_chart_04.pdf

this pdf gives you a look at the frames and sizes
 
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