This time around, we’ll be tackling some (well, almost all) of the electrical components of the band saw. When I bought the saw it was originally wired up with a 3 phase motor. The seller offered a discount if I didn’t want the motor. Since I don’t have a phase converter and to get it up and running would have required buying and configuring a VFD (variable frequency drive) or Rotary Phase Converter I opted to save the money and source my own single phase motor instead. Plus this allowed me to up size the motor if I wanted to get something bigger than the 1HP it had before.

This is the original motor starter and overload protection. I pulled the cover off of it to see what I was going to be dealing with.

Thankfully behind the cover it still had the original diagrams and instructions on it. This would prove helpful later on.

There was a torn off section, but enough of it was there to know what I needed to for getting it rewired for use with singe phase. I wouldn’t mind finding a full copy of this label though, because I’m not sure what the torn off section is showing, but it looks to be about wiring up high vs low voltage.

I made sure to document the location of the input wires before I started messing around with anything. That way I will be able to get it back to the way it was before, in case I don’t get things worked out correctly. This was easy enough, as they’re all in order, L1, L2, L3.

Noting the motor wiring was a little different, however. Since I didn’t have the motor, I don’t know exactly how it was wired up, but I can only assume, knowing it was 3-phase, that at some point an owner used a regular 3 conductor cable to wire it up. Here the Green is hooked up to T1, the Black is hooked up to T3, and white is hooked up to T2 (which appears to bypass the circuitry all together, and be tied directly in to L2). Confused yet? It’s not too bad, but we’ll get in to that further down.

Looking at the wiring diagram and associated documentation from above, it said that the wiring for single phase was actually simpler. Line in goes to L1 and L3, and then the motor leads come off of T1 and T3 (far left snippet). Pretty easy “In and Out” tracing on that one.
It also has a note that “Change Jumper A on starter from L2 to L3” (lower snippet). In the diagram, there is a line labeled A that goes from L2 in to the normally closed contact associated with the heater element for T3. This needed to move from T2 to T3 instead. This is represented by Blue (existing) and Green lines in the above image. Essentially, I had to make a new THHN wire that moved it over one terminal.
The last bit, was that the two Yellow circles is where the new black and white Hot/Hot wires will be attached for a single phase 220v motor.

This lower left red wire is the new Jumper A that I made. Diving in to this one reminded me of my hardline pc watercooling days.

After getting the motor starter squared away, I turned to the power supply end of it. I replaced the old duct taped up metal electrical box with a new waterproof box with waterproof strain relief. The power cord comes in through the metal cabinet and in to the box. From there the wires get tied together and the saw grounded, and the wire up runes out of the box up to the starter. The motor power cable comes down separately to go directly to the motor.

I picked up a 1.5hp motor, but that combined with the switch from 3 phase to single phase meant that my overload protection was under-rated for my motor.
These are heater elements that act as overload protection. They act as a sort of circuit breaker, but rather than tripping at a maximum amperage they simulate the thermal load of the motor itself. You install specific heaters that correspond to the full load amperage (FLA) of your motor. These heaters will heat up at the same rate as the motor, and once they reach a certain temperature a normally closed contact switch will open up and shut down the motor.
In this case, I went from H-24 to H-27 heaters, so they correspond to my 6.8 FLA motor. The details of that are probably less important than just saying, it is responsible for shutting down the motor before it overheats. This might happen at 7 amps, where it would never trip the circuit breaker being on a 20amp circuit.

The heater elements get installed around this post, with the two (missing) screws. That post is part of the normally closed contact that operates in overheat scenarios.

Phew. If you made it through all that, thanks and congrats? Here I’ve got cleaned it up with some electrical contact cleaner and a light brushing to knock off saw dust. I also got it wired back up for the input (top) and motor (bottom).

With the cover plate back on, I can say that I am happy with how that turned out. I’m glad that the existing starter and overload protection worked with my new single phase motor. I really wanted to keep the original look but wasn’t sure how until I dove in to it.
That was a pretty big mental hurdle to overcome. I hadn’t dealt with motor starters like this before, and certainly not with overload protection built in to it. That was a fun little project, and I am thankful for the diagrams and such still being behind the switch. Also, I’ll credit taking Basic Electricity (aka circuits) in high school, it always interested me and armed me with enough knowledge to research things like this and figure them out. Or at least know when to have the fire extinguisher near by during the “test phase” 🙂
Now the new single phase motor can be used along with original starter and overload protection, so the next thing we can do is work on getting the motor itself installed in the band saw. Subscribe to make sure you get notified when that comes around!
Thanks for checking it out.
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