Powermatic #66 switch

[David Ramby]

Last week I purchased a Powermatic #66 table saw to replace my Dewalt DW746. I believe it is a 1978 model. It has a Baldor 3 HP 3 phase motor and came with a Teco FM50 VFD. The saw was completely disassembled with new arbor bearings installed. Brought it home in boxes. Not yet sure if I will paint it or use as is. The only things I have found missing are the table insert, motor cover, miter guage, and on/off switch. Previous owner just used the VFD to control the saw. I would rather put it back together with a switch at the saw. Looking at the MM Tool Parts website they only list an on/off switch for the 5 HP 3 PH machine. What would be the best way to add a power switch at the saw?

[Stephen Bandirola]

Assuming that you have single phase 240 and are using the VFD to convert to 3 phase the correct way to switch the saw on and off is to use the VFD like the previous owner did.
You would put a switch on the saw wired to the trigger on the VFD.

The manual for that VFD is available online. I am using a similar Ebay version so I don't know the actual screw terminal numbers and programming screens of your unit but you just run light gage wire from the triggering screws on the VFD to any kind of simple switch and the go into the programming screen and set it use the remote instead of the front panel on off.

[Matt Day]

This is what I did to my Uni with FM50. A light switch works too, but that paddle gives some added safety.

[Bill Dufour]

I would install a illuminated stop start push button station. Wire it to the low voltage terminals on the vfd. Since installing a mushroom off switch I almost always use my knee to turn off the saw. My switch is mounted on horizontal conduit from a floor flange attached to the cabinet. Others bolt the switch box to the underside of the table.
Bill D

I would guess the control voltage is 5, 12, 15 or 24 volts. Match the LED voltage to that.

[Jeff Ramsey]

I've done this twice with two 3PH machines, and switched the two 220V load lines that feed the input side of the VFD.

[Matt Day]

Jeff, so you’re basically turning the power to the VFD on and off. I’m not sure that cycling the vfd that much is good for it, and I think you’d loose functions like motor braking and timed start up.

[Bill Dufour]

I've done this twice with two 3PH machines, and switched the two 220V load lines that feed the input side of the VFD.


This is very bad for the VFD unless you are powering the VFD off before disconnecting the input power. When shut down this way you lose dynamic braking but that power is still being generated. It goes into the output side of the VFD and it can overwelm the VFD and fry the device. You need to add a line reactor on the output side of the VFD to have any hope of it surviving for long.
Bil lD

[Jeff Ramsey]

This is very bad for the VFD unless you are powering the VFD off before disconnecting the input power. When shut down this way you lose dynamic braking but that power is still being generated. It goes into the output side of the VFD and it can overwelm the VFD and fry the device. You need to add a line reactor on the output side of the VFD to have any hope of it surviving for long.
Bil lD

Three years and counting with this technique on two machines with the same VFD, and no ill effects (also confirmed by the manufacturer as benign).

[Michael A. Tyree]

Cruise ebay and Amazon for switches, lots of industrial switches on ebay from regular sellers who buy up stuff. I've bought Chinese switches there too.

[Robert Hazelwood]

I would use the VFD controls with a remote low-voltage switch for general start-stop duty. You could then add a disconnect for the VFD for when you are changing blades or something. Alternatively you could unplug the VFD.