A couple of questions about a lathe motor swap

[luxige]

As a separate issue, giving the very high voltage and being 3-phase, it makes me think that the original motor was probably at least 5hp. If so, are you okay with the 80% reduction in potential torque?

Yeah, I was surprised that the old motor is only 3 hp, but that's what is on the data plate.

 

[luxige]

Good points Mark. I'm hoping the cap/s are mounted inside with the centrifugal switch. This was pulled from a multifunction woodworking machine with three of these motors. Worst case: the motors share one set of caps and I'll have to source new ones and figure out how to wire them in.
"Rung out" - always good to learn new lingo! I have done that. I'll be using three of the six modules. I don't think I'll be adding any auxiliary equipment, but I'll leave the other three modules stacked on there just in case.

Well, it looks like the worst case applies - I'll have to source new capacitors. There are two identical ones, see photo. A momentary start switch kicks in one for the start.
I haven't been able to find the exact part number. How close do the specs need to be?

 

[luxige]

Would one of these work?

(Second photo is AV ARCOTRONICS 40uF +-5% 1.27.6NAH MKP 420V 470V Capacitor)

 

[Alexander McGilton]

You have to be careful about using Start or Run capacitors. Start capacitors are designed for only short duty as they can burst if run too long. They are for a given capacitance; cheap, light and compact. Where as Run capacitors are more resilient capable of running continuously. You can use exclusively run capacitors knowing that they are bulky, expensive, and heavier. You may well use them for safety.

 

[luxige]

You have to be careful about using Start or Run capacitors. Start capacitors are designed for only short duty as they can burst if run too long. They are for a given capacitance; cheap, light and compact. Where as Run capacitors are more resilient capable of running continuously. You can use exclusively run capacitors knowing that they are bulky, expensive, and heavier. You may well use them for safety.

Ok, once again very helpful! I vaguely remember reading about that, definitely needed the reminder...
How can I tell if it’s rated for Run duty?
The one in the picture on the left (post #13) is specified as a Run cap in the auction listing. I would guess that fits with the “-R” after the part number. The other two auction listings don’t specifically say Run or Start.

BTW, all of these are the same capacitance as the stock part, but the voltage specs are all a bit off of the specified 400V. Is that a spec I need to match?

 

[Alexander McGilton]

It should be fine using a 440v in the place of a 400v.

"They Come in a Variety of Sizes and you will need to know your Microfareds or uF also the voltage however you can use a 440Volt in place of a 370Volt but not a 370 in place of a 440Volt. The Microfareds must stay the same within 5% of it's original value. "

Round Dual Run Capacitors :: Run Capacitors :: Air Conditioner Parts :: Just The Right Air . com

Round Dual Run Capacitors,used in starting the compressor and condenser fan motor at the same time

web.archive.org

 

[luxige]

It should be fine using a 440v in the place of a 400v.

"They Come in a Variety of Sizes and you will need to know your Microfareds or uF also the voltage however you can use a 440Volt in place of a 370Volt but not a 370 in place of a 440Volt. The Microfareds must stay the same within 5% of it's original value. "

Round Dual Run Capacitors :: Run Capacitors :: Air Conditioner Parts :: Just The Right Air . com

Round Dual Run Capacitors,used in starting the compressor and condenser fan motor at the same time

web.archive.org

Thanks. I ordered two of the CBB65-R. Turns out the R means “round.”
Now I’m thinking about adding a centrifugal switch to cut out the start cap. The other machine uses a momentary switch to start, and I’d rather just use the shift lever without also having to push a start button. Thoughts?

 

[Alexander McGilton]

Did it not already come with a centrifugal switch? Since the starting coil only runs momentary some manufactures use this as a means to get away with smaller gauge wires than are capable of running continuously. How was the motor original configured?

 

[luxige]

No centrifugal switch, it was set up like a typical woodworking machine. To start, you turn a spring-loaded switch which closes the contactor and also energizes the start cap. When the motor comes up, you release the switch and it springs back to n/o. So the operator is taking the place of a centrifugal switch to cut out the start cap, while the contactor keeps its own coil energized until you hit one of the several stop buttons.

I can't pull all this stuff from the machine and transplant it as-is because I need it to run the other two motors. It's in storage and I only had a few minutes yesterday to pop in and discover the pair of capacitors that are shared by the three motors. I'll make time today or tomorrow to dig in and trace all the wiring so I can just duplicate it. (If anyone's interested, it's a Robland X31 and I'm removing the shaper spindle, keeping the saw and jointer/planer).

It looks like there is no room inside the motor housing to squeeze in a centrifugal switch, so it would have to be mounted outboard. I'll have to wait until I get the gearbox installed to see if that could work.

 

[markba633csi]

The cap you ordered should work fine
"ringing out" is a term from even before my time; it refers to testing a motor or generator armature on a fixture that buzzes when there is a shorted
segment on the commutator- I think