Delta Unisaw from 1980/85 wiring question

Joe.......a couple of years ago, I had an electrical issue with my Unisaw that involved the wiring in the cabinet and the wiring in that external magnetic starter box on the back of the saw. I contacted a local electrical contractor.......explained my situation and described what I needed.......they treated the job as a piece of cake......gave the job to one of their senior electricians as a break from their normal daily duties.......I cleaned the saw up real well......inside and out......the guy came out......studied everything for a couple of minutes......knew exactly what was what......and made the repair......he had all kinds of neat little gadgets that allowed him to secure the wires to the inside of the cabinet......devices that I never knew existed......did the rewiring necessary in that magnetic starter box (which keep my dumb butt out of it).......and we had a pleasant conversation about my shop and woodworking.......and my saw was back to working perfectly......cost me about $100......money well spent (and I'm half Dutch).

The low voltage starter in the box includes a transformer and solenoid that does several things: separates the 220 v current to your motor and a safer 24 v to your on/off switch, provides overload protection that will turn off the motor if the current gets too high, and prevents the saw from re-starting on its own if it was in use during a power outage.

The overload protection is provided by some (two for single phase, three for three phase)  "heaters" (small bimetal strips) that must be matched to the current rating of the motor. If the current is too high the bimetal strips bend and open a contact, shutting off your motor. 

Since you upped the hp of your motor it will also be higher amp rated and those heaters will need be changed to some that match the current rating of the new motor. Otherwise you risk having the motor cut out while under what would be normal loads for your higher hp motor. You also don't want to have the heaters be rated for higher amps than your motor otherwise you risk damaging the motor by running it at too high amperage. Heater size charts are available online at many motor control supply places online.

There should be a wiring diagram inside the lid of the low voltage box. If not, you might try asking over at OWWM.org in their Electrical subforum (free but registration required).

Roger, Gary - thanks.  The saw runs fine.  I do not need any repairs at this time.  I'm just looking to understand how to insert a safety switch into the loop and locate it more conveniently on the left side of the saw rather than the right.  

When I swapped the motors, I also swapped all of the wires and electronics, so the Starter box and on/off switch moved with the motor.  Everything is still matched up.

For what it is worth, I did more digging last night and found, what I think is the owners manual for the starter box.  I'll have to take the cover off again to see if the electronics match one of the photos in the guide.  Here is the source:

http://vintagemachinery.org/pubs/1141/2437.pdf

Based upon this document, I think the device might also convert 3-phase motor to single phase?  That's not my situation, but the box seems to be wired for multiple scenarios.

Interestingly, the 1-1/2 hp saw did not have this box.  Instead, it had a full magnetic switch in the front switch box with a reset button.  Nothing on the back.

Maybe what I'm really asking:  Does a modern VFD (variable frequency drive) replace the function of this electromechanical device?

Thanks Bill.  I'll absorb that a bit.  

This is why WC is so good.

Added later 15 min 53 s:

Bill,

Got into my box.  It matches Figure 5, but is wired for single phase.  Based upon what Bill just shared, it looks like I can remove the existing on/off switch and replace it with the new switch, located where I prefer.  My existing switch has the normally closed (NC) terminal wired to #1 and the normally open (NO) wired to the #3, with the white "common" wire connected to #2, as illustrated in wiring diagram.  As long as my new switch has NO and NC positions, I can do the replacement.

Joe

Added later 07 min 20 s:

Actually, now that I understand what I have, I might just relocate the existing switch and build a homemade paddle to depress the stop button.

Seems like you are on your way to getting it running and, hopefully, stopping!

If you are successful in moving the switch to the left and don't electrocute yourself.......I'd like to do the same......left side is one of the few things preferable to the right side I can think of.......included a pic of my homemade safety paddle.......

Assuming there is enough cord length, I'll move the whole switch assembly to the left.  Otherwise, I'll cut up an extension cord to get a long enough cord length.  I'll probably mount it similarly to how you have yours.  I have the older style saw with the switch mounted on a 1/2" threaded pipe to the underside of the table.  There isn't a pipe thread on the left, so I'll either mount to the cabinet like you and build it forward for easier reach, or hang it on one of the fence bolt holes.  Because the hand wheel swings left, I have to leave enough space for cranking the hand wheel when at the 45 degree angle.

Joe......I'll post a pic of my shop made safety switch from the side and hope that it helps you in making a safety switch of your own......on my Uni there is a section of pipe that comes down to hold the power switch.......I attached a couple pieces of wood like a clamp on that pipe which gave me a platform to build on.......having a safety turn off is very desirable......just a bump of the knee turns the saw off.......

image hosting

Roger,

Great photo.  At least 1000 words worth.  Thanks.

Joe

Joe......there are two boards in the background that seem to be a part of the safety switch......just disregard them......sorry about that......

the two boards I placed around that pipe.......one in the back is just a straight board.......but, the one in front is shaped like a T......with the middle of that T extending forward and is drilled for a screw which allows the safety board to rotate/pivot.....

I've been meaning to do this for my same vintage Unisaw for a long time. Thanks for the picture, Roger. Now I may actually do it.

Thanks to both Joe and Gary........it does warm the recesses of my dark heart to think I've shared something that might make fellow woodworkers safer........

Most likely, you need to see a doctor for some penicillin.......

LOL - you guys crack me up.