# Three Phase Motor



## matthewsx (Sep 5, 2021)

Swapped out the motor on my lathe, trusty HF engine hoist for the win again.




John


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## matthewsx (Sep 6, 2021)

I'm setting up the controls now and have a question for folks who have done this conversion. On my other lathe I just have a simple on/off and speed control with a tach so I know what my spindle rpm is. For those who have done braking, jog, proximity stops, etc. how useful is all that stuff? Do you use it everyday, just for special setups, or is it something that you have because it's an available feature?

Also, how useful do you find a DRO setup on a smallish lathe? 

John


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## rabler (Sep 6, 2021)

My lathe has a apron clutch/brake lever, so I don't use that on the VFD, or jog, etc.  I love having a DRO on the carriage as there is otherwise not a quick Z measurement, was just using it for drilling holes in the end of a shaft.  Significantly easier in my mind that a carriage stop.  I still tend toward the dials more for the cross-slide measure, even though I paid the money for a high resolution cross-slide scale.


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## Ischgl99 (Sep 13, 2021)

I did things differently than most here.  I haven’t installed a speed pot for variable speed yet, that will come some day.  I find I don’t really need it very often since it is easy to change speeds on my lathe, and I retain full HP.  Once I install a DRO, I am going to see if I can add a constant surface speed based on the cross slide position.  I don’t know yet if that will work, but should be a fun project to try.

I mostly thread metric, so I decided to install a switch I use for threading that does fast braking and also reduces the VFD speed in half.  I keep the belt on the highest speed pulley, so that gives me about 100 rpm on my 1236T for the lowest gear setting, and then can use higher gears if I want more speed.  This also works if I want in between speeds for normal turning operations.  Since I need to keep the threading lever engaged and need to run the lathe in reverse to start the next pass, I repurposed the jog button to give me full speed when depressed to cut down the time reversing to the starting position.  

I don’t miss the jog button, I just use the forward/reverse lever to bump the spindle if needed, but most of the time I just switch to the highest gear setting and spin it by hand.  If you have buttons to press for forward and reverse, that would not work as easily.


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## B2 (Sep 14, 2021)

On Saturday I posted my VFD conversion which has all of the tricks I could think of. I really like having the DRO and the RMP.  I also like having read out of the VFD frequency indication prior to actually turning on the motor.  Use these all the time.  The proximity detection is great if you want to thread or if you want to run right up to a stopping point... in either +-Z direction.  The ultra slow jog in either direction is handy.  While doing the conversion I put in two speed braking and only use the more aggressive braking (1 second) for the proximity work.  I figure the slower braking (3 seconds) is easier on the wear and tear of the machine.  I also added a switch for automatic oiling, but have yet to even try my oil pump out.  Anyway, lots of safety features.  

https://www.hobby-machinist.com/thr...tronic-components-pm1440gt-vfd-3-phase.95058/ 

If you want to look at it I would welcome your thoughts. 

Dave


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