VFD on Lathe with Coolant Pump

I recently purchased a second hand AcraTurn 1340 engine lathe, essentially a different version of the Girzzly G0709. This lathe has a built in coolant pump that I assume to be a Single phase 110V pump (since I see the transformer in the electrical cabinet tapped for 110). Since the lathe is 3 phase, I'll be using a VFD to convert from single phase, but how do I handle the coolant pump? Since I want to be connecting the output of the VFD directly to the motor, how can I also run the coolant pump?

mesa said:

I recently purchased a second hand AcraTurn 1340 engine lathe, essentially a different version of the Girzzly G0709. This lathe has a built in coolant pump that I assume to be a Single phase 110V pump (since I see the transformer in the electrical cabinet tapped for 110).

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You would do well to post a wiring diagram of the lathe if you have or can get one. I would be inclined to believe that the step down transformer is for control electronics depending on vintage, newer stuff tends to use 24volt stuff but lots of 60's-70's-80's machine tools used 110v power to the control switches to actuate contactors to drive things like the spindle motor & coolant pump.

Since the lathe is 3 phase, I'll be using a VFD to convert from single phase, but how do I handle the coolant pump? Since I want to be connecting the output of the VFD directly to the motor, how can I also run the coolant pump?

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Is the transformer a 3 phase unit or single phase (how many incoming/outgoing power wires are there?) If its single phase (and I'm assuming it is) just wire it to your incoming L1/L2 power, take the L1/L2 power going from the disconnect to the contactors and put it to the VFD input terminals and use the contactors as oversized relays to switch the logic inputs on your VFD.

I am assuming it is a 220/440 motor? How is the motor wired originally(high-voltage or low-voltage)? If it's 440 V that is a little bigger of a deal. But, if it's 220 V, just bring the two of the natural Single phase through one of the VFD relays. What kind of VFD are you using?

Eh, maybe just run the VFD to spindle motor, use the existing controls to start and stop the VFD via the control inputs, and keep the pump as it is.

greenbuggy said:

You would do well to post a wiring diagram of the lathe if you have or can get one. I would be inclined to believe that the step down transformer is for control electronics depending on vintage, newer stuff tends to use 24volt stuff but lots of 60's-70's-80's machine tools used 110v power to the control switches to actuate contactors to drive things like the spindle motor & coolant pump.




Is the transformer a 3 phase unit or single phase (how many incoming/outgoing power wires are there?) If its single phase (and I'm assuming it is) just wire it to your incoming L1/L2 power, take the L1/L2 power going from the disconnect to the contactors and put it to the VFD input terminals and use the contactors as oversized relays to switch the logic inputs on your VFD.

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I got the schematics(link), you're right the transformer is only for control voltages, it turns out the pump is 3 phase as well.

I think the control stuff makes sense... if I have it right you're saying to split my incoming 1-Phase 240V, to goto both the VFD power-in and the transformer, to maintain all the control voltages. Then, I'll disconnect the contactors that were previously switching the motor itself, and instead wire them to switch the inputs on the VFD, then wire the VFD output to the motor?

What I don't understand is how I can have the coolant pump remain 3 phase with the ability to turn it on and off separate from the spindle. I've seen some say that since the coolant pump is a small load relative to the main motor, it can be switched after the VFD, but I've never seen that confirmed.

For reference my VFD is a Fuji Electric Frenic-Mini. FRN12C2S-7U | Fuji Electric | AC Drives

mesa said:

I think the control stuff makes sense... if I have it right you're saying to split my incoming 1-Phase 240V, to goto both the VFD power-in and the transformer, to maintain all the control voltages. Then, I'll disconnect the contactors that were previously switching the motor itself, and instead wire them to switch the inputs on the VFD, then wire the VFD output to the motor?

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Yep.

What I don't understand is how I can have the coolant pump remain 3 phase with the ability to turn it on and off separate from the spindle. I've seen some say that since the coolant pump is a small load relative to the main motor, it can be switched after the VFD, but I've never seen that confirmed.

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You could probably get away with that, but its bad practice. Depending on what kind of coolant pump we're talking about cheapest option is probably to just get a single phase little giant or something similar to replace it that will run on 220V single phase. More expensive option would be a second smaller VFD to convert power for the existing pump from single phase. I've got a little Motortronics micro VFD to power the 1/5 HP pump on my Howa because throwing a different pump in the existing pump's location was going to either be really expensive or a big pain in the ass.

greenbuggy said:

You could probably get away with that, but its bad practice. Depending on what kind of coolant pump we're talking about cheapest option is probably to just get a single phase little giant or something similar to replace it that will run on 220V single phase.

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Seems like this is the way to go. I'd assume its ok to split the 1-Phase 240V thats feeding the VFD to go off to the pump and its controls?

Also, I was thinking more, since the VFD control inputs are 24VDC, and it's capable of providing 24VDC from its PLC pin, is there any reason to not just use the lathe switches to switch the 24VDC and ignore the contactors/transformer all together? Presumably if they can switch 110VAC then they can switch 24VDC @ 50 mA.

mesa said:

Seems like this is the way to go. I'd assume its ok to split the 1-Phase 240V thats feeding the VFD to go off to the pump and its controls?

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Shouldn't be hard to do. You will need considerably smaller wires for the pump since I doubt its even half a horse.

Also, I was thinking more, since the VFD control inputs are 24VDC, and it's capable of providing 24VDC from its PLC pin, is there any reason to not just use the lathe switches to switch the 24VDC and ignore the contactors/transformer all together? Presumably if they can switch 110VAC then they can switch 24VDC @ 50 mA.

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On my lathe I kept the controls to run logic inputs on the VFD because it was easier to do so than integrating the foot brake switch into the VFD logic. I did use the "jog" button direct to the VFD logic inputs. YMMV. Make sure you use quality shielded cable for VFD logic supply and inputs whatever you do (I happen to like Lapp Olflex myself), and make sure to pay attention to the VFD logic power so you aren't feeding +48V to something it might fry.

I do not want to hijack this thread but it seems you fellas have a good amount of knowledge and I need some help with.
I am in the market for a VFD and would like a little help on just where to buy and reputation of the manufacture from some with experience in this area. I have a Millrite MVN powered by a Dayton 3 Phase, 2 hp, 3450 rpm on 208-220/440 volt power. But I have single phase service and have read how the VFD might just be what I need, help me out if you can.
Thanks
Nelson

my email is nel2lar (AT) yahoo (DOT) com Thank you