Converting Sawstop Industrial saw from 7.5 hp 3phase to 3 hp single.

[Ben Rivenbark]

Hey guys, I've found a Sawstop 7.5 hp 3 phase cabinet saw for just a couple hundred dollars, but I need to convert it to single phase. A VFD would be expensive for one that could run a 7.5 hp motor and I'd rather not have to worry about turning on a rotary converter everytime I want to use my saw, not to mention the extra noise . I have a spare 3 hp motor from a 15" planer that I can tig weld tabs on to match the sawstop motor mount. From wiring schematics, it appears that the contactor switch box is the same with the exception that the three phase box contains transformer that ouputs 220v for the other controls.

The saw is actually one of the CB models, that was renamed the industrial cabinet saw around the time the professional saw was introduced. Not sure if that makes a huge difference.

If anyone has any advice for me going forward with this, or warnings of pitfalls, etc, I'd be thankful.


Carpe Diem,



Ben

[Rich Riddle]

My advise to you is to come to peace with a rotary phase converter. They engineer these saws and the trunnions, technology, etc. for the size motor in question. You can get a fairly quiet RPC up and running. As you know that's a far less expensive option. Once I purchased one three-phase tool, it made getting more of the 3-phase tools a better and more cost-effective option.

[Cary Falk]

What would be going through my head would be "if I jerry rig this thing will the brake fire when needed, or did I miss something." I think I would have to do a test fire after I was done.I thinks I read some time ago something similar and SawStop helped with the conversion and took the motor in for a partial trade.

[Ben Rivel]

Definitely give SawStop a call on this one, they are really the only ones qualified to answer this question.

[Erik Loza]

How much would one of those Chinese inverters really cost?

Erik

[Nick Nelson]

I agree with using a converter, I'm sure you won't we able to hear it when the saw is running it's just a little hum.

[Chris Padilla]

Since you basically stole the SS, you can pony up for a nice RPC to run it and still be miles ahead.

Otherwise, I'd give SS a call as suggested.

[Ken Fitzgerald]

I would confirm with SS that it will function properly on a phase converter. If it will, I'd purchase one. In the end, it might be the cheapest alternative.

[Silas Smith]

Have you considered a static phase converter? Even with the loss of power, you still have more than 3hp.

[Ben Rivenbark]

How much would one of those Chinese inverters really cost?

Erik

It's actually more than just cost; here's some info from a machinist forum where someone wanted to run a VFD/inverter with a 7.5 hp motor:

All VFDs can convert single phase to 3 phase. But beyond around 3HP at 230V, you have to double the size of the VFD. So for your 7.5HP motor, you will have to use a 15HP VFD. Also consider this; a 7.5HP 230V 3 phase motor will be around 22A FLC. That means it will be drawing 38A from the single phase line when fully loaded. But to use the 15HP VFD you have another problem with meeting the NEC. You are required to size the service for the VFD at 125% of the VFD's maximum current rating, not the motor's. So looking at an average 15HP VFD, it's rated for 46A so the circuit to feed it must be at least 57.5A and the nearest size is going to be 60A. So keep that in mind; you will have to run a 60A circuit breaker and cables to a VFD for a 7.5HP motor. It's a little gotcha...

[Ben Rivenbark]

I did speak with SawStop and found the same as many other individuals; they are very helpful and provide great customer service. The tech gave me a list of parts that I'd need to make the conversion, so I'll post it here for posterity.


CB105 007 - Contactor Box 3HP/208-240V/1-phase
CB104 055 - Specification Label (3HP/1PH/230 Volt)
CB104 069 - 3HP, 1PH, 208-240V, 60Hz, TEFC Motor
CB104 076 - ICS Motor Pulley
CB104 077 - M5x5x30 Key
CB104 078 - M6x1.0x8 Set Screw X2
CB10 WA020 - Switch Box Assembly


That get's me out for a pretty decent price, so I think I'll look into Rotary phase converters once I get a milling machine and metal lathe

[David L Morse]

Have you considered a static phase converter? Even with the loss of power, you still have more than 3hp.

If your usage is limited to 3Hp this should be the first option to consider. Check with Sawstop to be sure you are powering the two leads that supply their electronics.

[Bruce Page]

I've been running a static converter on two 3ph machines for over 20 years without a single hiccup. You loose a little HP with a static converter but with 7.5hp you'd still have HP to spare.

[Martin Wasner]

Put a 5hp single phase motor in it. I seriously doubt they're doing anything different with the guts of the saw to mount the 7-1/2hp motor.

Pretty easy to call them and find out.

[Ben Rivel]

I did speak with SawStop and found the same as many other individuals; they are very helpful and provide great customer service. The tech gave me a list of parts that I'd need to make the conversion, so I'll post it here for posterity.


CB105 007 - Contactor Box 3HP/208-240V/1-phase
CB104 055 - Specification Label (3HP/1PH/230 Volt)
CB104 069 - 3HP, 1PH, 208-240V, 60Hz, TEFC Motor
CB104 076 - ICS Motor Pulley
CB104 077 - M5x5x30 Key
CB104 078 - M6x1.0x8 Set Screw X2
CB10 WA020 - Switch Box Assembly


That get's me out for a pretty decent price, so I think I'll look into Rotary phase converters once I get a milling machine and metal lathe

Just out of curiosity, what did they quote you for all that?