troubleshooting a Scotchman cold saw

My cold saw stopped working last night and I am trying to figure out why.


Scotchman 350 cold saw, 22/44rpm, 230v 3 phase working through a static phase converter


Symptom: Pull the trigger, nothing happens. other 230v items on the circuit are working. If I manually push down what I call the "contactor" ( main wiring from converter goes in on one side with 110v wiring on other for coolant pump) everything seems to work. I removed the cover to the trigger switch and jumpered the contacts and it still doesnt work. Tracing the wiring, from the main input on the "contactor", there is wires going to a a second block that has marking for 230 and 460.(by the diagram, the wiring is correct for 230). This block has a large fuse in it which I am assuming is good based on saw working as described above. Opposit the jumpers is a second set of terminals marked "option" and 24 which I am assuming is the power for the controls. ONe wire coming off of the 24 side is going to what looks to be a fancy terminal strip where the trigger switch wiring is connected to as well. JUst from looking at it, it appears the wire from the 24 side goes to one side of the switch and returns via the second wire of the switch turning into a very light gauge (26?) that is marked "5" this wire goes down into the motor. In the same sleeve is a similar gauge wire marked "6" that is going to a terminal on the "contactor" marked "A1". I just borrowed a voltmeter from a friend so I am thinking my next step is to verify voltage? After that, I have no clue. I know very little about 230v so any assistance y'all can give with the piss poor information I provided above is greatly appreciated. I don't have internet at my shop (I'd get nothing done if I did) so I will try to get some pictures and more info and report back

Thanks to all

Scott

Scott,

I would certainly pull the fuse you mentioned and check it with an meter to verify its condition. I wonder if that light gauge wire that goes into, then comes out of the motor heading to the coil could be a thermal switch embedded in the windings. Did you work the saw hard the last time you used it? If that's a thermal O/L in the winding it may be stuck open.

Stuart

i got back to shop with meter, verified fuse was good, 26v at the 24v side. I had previously made sure all the terminals were tight. For kicks, i hit the trigger and it started working. put it all back together and had no issues the rest of day. I had been cutting 3x3" x 3/16" square tubing at 45degree and many other cuts with multiple repeats against the saw stop so it definitely was getting some work. I can't see it taking 12 hours to cool off so maybe the thermal switch is getting wonky. If it happens again, I'm guessing my options are to bypass the thermal switch ( not a good idea but a means to troubleshoot), or pull the motor and take to a shop for service. Saw was used when I got it. Don't remember the age but it has been doing me right for 2 years. Wonder what the average 3hp, 3phase motor repair costs

sounds like a flaky coil circuit to me - anything from the starter coil itself to the terminal blocks and trigger. I wouldn't be looking at the motor at this point at all.

Ken,

A thermal O/L is in the coil circuit, that's how it works. This wiring diagram shows the thermal and wire numbers...it's not uncommon for them to stick open after tripping.


http://pacific.sdsu.edu/cfd/fabrication_facility/cold saw.pdf

Stuart

Of course you are right Stuart, I missed the part about the thermals being in the motor. Before pulling the motor for service, I would bypass the click switch and put in a simple set of overloads.

I had a similar problem with mine. I called scotchman and they sent me a new switch, fixed it and I am back in business.