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Do 3-phase PM machines come wired VFD friendly?

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Djl338

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#1
I am looking at the 1236-t or 1340gt, lathes and both are optioned with the 3-phase motor. I have a pm-932 mill with a vfd, and I’m sold on it as a great upgrade. Just wondering what’s needed electrically to hook to the vfd (motor at least I guess) when the 3-phase machine arrives, I’ve read through the posts on conversions and what I’ve read seem like they started life as single phase and converted
Thanks!
David
 

Bob Korves

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The motor gets connected to the VFD, and the existing controls are disconnected. It is possible to use the lathe controls to control the low voltage side of the VFD, but they must first be disconnected from the original circuits. Switches and other controls between the VFD output and the machine will cause big problems, just don't do it.
 
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Nogoingback

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#3
You didn't mention what kind of power you have in your shop. You might know this already, but if you have single phase power
only, you can get a VFD that converts it to 3 phase.
 

Djl338

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You didn't mention what kind of power you have in your shop. You might know this already, but if you have single phase power
only, you can get a VFD that converts it to 3 phase.
I have single phase, so a vfd was part of the plan if I decide to go that route. I was trying to make out what’s on the control panel of the 1340. Guess a fwd-rev, emergency stop and power. So a potentiometer needed. Some of the schematics and threads I’ve read on it seem pretty intimidating. The 932 mill was fairly straight-forward, for some reason there seems like more to wiring the lathe safely
 

mksj

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Simple answer is no, and that also applies for other 3 phase lathes w/o a factory VFD install. There is a fundamental difference in that the native machine switches the motor high voltage motor connections, and typically the relays/contactors, controls work off of 24 VAC, or 120 VAC for larger lathes. If you connect the VFD run inputs directly to the spindle switches you bypass all the interlocks and safety controls.

If you want to retain the safety features and have the lathe work pretty much as if it was connected to 3 phase directly, then I previously outlined a fairly simple conversion which uses the contactors to switch the VFD low voltage control inputs. Not ideal, but as long as the contactors are new, the contact resistance/function should be acceptable. The basic conversion outlined takes maybe 1-2 hours to do and is very simple. You will spend a lot more time on building the VFD enclosure and outfitting it to a level you want. This information has been also previously posted. WIth a VFD, you have the added benefit of speed control and quicker braking. On a lathe, it is highly advisable to use an external braking resistor to get quicker braking times. I would also get a decent VFD, the WJ200-015SF that Matt sells and the parameters are included in the posting below. More recently I have also been using Yaskawa VFDs, but more complex and costly. The stock motor is decent enough and most individuals use a 20-90Hz speed range in sensorless vector control. This decreases the need to switch belts if used in the lower speed setting, or an alternative is to flip the motor pulley so the larger motor pulley goes to the larger headstock pulley, you will need a longer belt. This along with a 90Hz top motor speed will give you ~ the same top end spindle speed of 1800 RPM and no belt changes for low to high (this applies to the 1236GT/1340GT).

If you can swing the 1340GT, I think you will really enjoy it with the added VFD capabilities.

https://www.hobby-machinist.com/thr...l-board-and-switches.49022/page-2#post-564068
 

Djl338

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#6
Simple answer is no, and that also applies for other 3 phase lathes w/o a factory VFD install. There is a fundamental difference in that the native machine switches the motor high voltage motor connections, and typically the relays/contactors, controls work off of 24 VAC, or 120 VAC for larger lathes. If you connect the VFD run inputs directly to the spindle switches you bypass all the interlocks and safety controls.

If you want to retain the safety features and have the lathe work pretty much as if it was connected to 3 phase directly, then I previously outlined a fairly simple conversion which uses the contactors to switch the VFD low voltage control inputs. Not ideal, but as long as the contactors are new, the contact resistance/function should be acceptable. The basic conversion outlined takes maybe 1-2 hours to do and is very simple. You will spend a lot more time on building the VFD enclosure and outfitting it to a level you want. This information has been also previously posted. WIth a VFD, you have the added benefit of speed control and quicker braking. On a lathe, it is highly advisable to use an external braking resistor to get quicker braking times. I would also get a decent VFD, the WJ200-015SF that Matt sells and the parameters are included in the posting below. More recently I have also been using Yaskawa VFDs, but more complex and costly. The stock motor is decent enough and most individuals use a 20-90Hz speed range in sensorless vector control. This decreases the need to switch belts if used in the lower speed setting, or an alternative is to flip the motor pulley so the larger motor pulley goes to the larger headstock pulley, you will need a longer belt. This along with a 90Hz top motor speed will give you ~ the same top end spindle speed of 1800 RPM and no belt changes for low to high (this applies to the 1236GT/1340GT).

If you can swing the 1340GT, I think you will really enjoy it with the added VFD capabilities.

https://www.hobby-machinist.com/thr...l-board-and-switches.49022/page-2#post-564068
Thank you Mark, I missed that post. Reading through that makes it seems much less of a hurdle and more of a worth the small amount of extra effort and expense. The vfd on my mill made it much more precise and controllable, I image the same results and usability on the lathe. I used a teco Unit on the pm-932, it was super easy program, seems like the wj200 works best via pc programming from previous posts, not a problem and the instruction you provided makes sense to go that route . Honestly it’s more machine than I need but it’s a nice machine for the cost.
Thanks very much, you’re quite an asset to the forum !
 

Djl338

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#7
“alternative is to flip the motor pulley so the larger motor pulley goes to the larger headstock pulley, you will need a longer belt. This along with a 90Hz top motor speed will give you ~ the same top end spindle speed of 1800 RPM and no belt changes for low to high (this applies to the 1236GT/1340GT).”

Mark, do you have a part number/belt size to use this pulley setup?
Thanks
 
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