# Convert 3 phase to 1 phase?



## KAD (Jun 15, 2014)

With all the used lathes out there set up for 3PH is it possible to swap the motor out with a 220 1PH?  I imagine the base would need to be modified for the bolt pattern, but could I find a motor with matching arbor size?  Anyone ever do it? Thinking about a SB 10 with motor mounted below inside cabinet.


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## CluelessNewB (Jun 15, 2014)

Keep the 3 phase motor and add a VFD (Variable Frequency Drive) to convert your single phase power to 3 phase and add variable speed as an added bonus.   Cost for a VFD is about the same as a single phase motor.


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## nickmckinney (Jun 15, 2014)

CluelessNewB said:


> Keep the 3 phase motor and add a VFD (Variable Frequency Drive) to convert your single phase power to 3 phase and add variable speed as an added bonus.   Cost for a VFD is about the same as a single phase motor.




If its 3HP or less a VFD is definitely the best way to go.


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## davidh (Jun 15, 2014)

they whom came before me, beat me to it............................... VFD is the only way to go................


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## CluelessNewB (Jun 15, 2014)

Here are some pictures of the VFD installed on my Logan 820.  The first picture shows the actual VFD (the tan colored TECO box).   The white toggle switch just shuts off power to the VFD and is really not required.  The gray box just covers up the wire terminals it has holes drilled for ventilation.   You can also see the original 3 phase motor, an oldie but goodie! The second picture shows the controls start, stop, speed and forward/reverse.  I would have used the original [Forward - Off - Reverse] drum switch but it was busted by the previous owner.


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## newbydave (Jun 15, 2014)

Cluelessnewb,
What type of belt do you have on your 820?


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## KAD (Jun 15, 2014)

Wow - that's it? I thought a VFD would involve a complex panel setup. Thanks guys.


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## CluelessNewB (Jun 16, 2014)

newbydave said:


> Cluelessnewb,
> What type of belt do you have on your 820?



The belt is the style with clips, no need to remove the spindle, some people don't like them but it works for me.  I got mine from Ebay about $25 including shipping.


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## echesak (Jun 16, 2014)

KAD said:


> Wow - that's it? I thought a VFD would involve a complex panel setup. Thanks guys.



I enclose mine in a metal enclosure, with the buttons and such.  It protects it from dust and chips, but requires a fan to vent the enclosure.  I've got VFD's on a J-head Bridgeport, Clausing lathe and a Do-all band saw.  Definitely the way to go.  

Here's the one on my Clausing Lathe, using an Automation Direct VFD.  

Eric


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## nickmckinney (Jun 16, 2014)

KAD said:


> Wow - that's it? I thought a VFD would involve a complex panel setup. Thanks guys.



I attached mine to a piece of scrap PVC pipe, you can see it behind the lamp shade.


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## Andre (Jun 16, 2014)

3ph motors run smoother than single phase motors. Another vote for a phase converter. But keep in mind, a vfd can wrenck your motor. If you lower motor speed and start to hear it whine or squeal, that's a bad thing. You can change speeds using a VFD, but if the motor whines back up a little untill it stops whining.


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## JimDawson (Jun 16, 2014)

Here's mine on my mill, just hanging out in open air.  It's up high enough to keep the chips out, in about the same position as the original switch.  Some day I'll get my control panel finished and get it mounted inside the electrical cabinet.


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## Mr Ron (Jun 16, 2014)

CluelessNewB said:


> Keep the 3 phase motor and add a VFD (Variable Frequency Drive) to convert your single phase power to 3 phase and add variable speed as an added bonus.   Cost for a VFD is about the same as a single phase motor.



If I were to put a VFD on a belt driven lathe, where would I place the belts? On the lowest speed or the highest?


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## cjtoombs (Jun 16, 2014)

A VFD's speed range depends on how oversize the motor is.  You can drive a motor to twice it's rated speed, beyond that you are flirting with exploding the rotor due to centrifugal force exceeding its strength.  From the rated speed through its highest available speed, the VFD will give full rated horsepower.  Below its rated speed, they will generally try to give constant torque.  What that means is is that the horsepower will drop off proportional to speed.  So that if you have a 1 hp, 1750 RPM motor, at 875 RPM you will have a half horsepower motor.  So, if you double the horsepower you actually need, you can get a 4:1 speed range from a VFD.  So it is likely that you will still need to use some of the belt ratios as well as back gear to get the speed range you need for a lathe, which we would like to be very wide.  Of course, if you don't use much power at the low speeds, then it may not be an issue, but when it bogs the motor in the middle of the cutting a thread is not a good time to find that out.  I have that issue with my Tormach mill, basically to run a 4" HSS slitting saw in mild steel, you have to run it at 200+ FPM cutting speed and take very shallow cuts, or it will bog the cutter down.


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## JimDawson (Jun 16, 2014)

Mr Ron said:


> If I were to put a VFD on a belt driven lathe, where would I place the belts? On the lowest speed or the highest?




For general turning, I would start by placing the belts where you run the lathe the most.  If you need major speed changes, I would move the belts to the proper speed and use the VFD to make the fine speed adjustments and to achieve speeds between the belt positions.  This keeps your motor running in a speed range where it's happy.


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## CluelessNewB (Jun 16, 2014)

Mr Ron said:


> If I were to put a VFD on a belt driven lathe, where would I place the belts? On the lowest speed or the highest?



You shouldn't think of the VFD as a replacement for your belt speeds just fine tuning and a bit more range at the two ends.  You don't want to run the motor too slow because of lost power and loss of cooling from the motor internal fan.  You don't want to run it too fast because it most probably isn't designed for that.  I have my lathe VFD set up for a minimum or 30hz (half of 60hz) and a maximum of 90 hz (1.5 x 60).  I don't really have any scientific data to support these numbers just seat of the pants engineering.    Typically I run at the normal 60 hz and tweak as required.  

I also have VFD's on my wood shaper, wood jointer and a belt/disk sander.  For the most part I run them at 60hz except I do tweak the shaper a bit depending on wood species and the cutter I am running.


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## Andre (Jun 16, 2014)

cjtoombs said:


> A VFD's speed range depends on how oversize the motor is.  You can drive a motor to twice it's rated speed.



Yes, you CAN, but you will significantly reduce the life of the motors bearings and brushes.


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## John Hasler (Jun 16, 2014)

Andre said:


> Yes, you CAN, but you will significantly reduce the life of the motors bearings and brushes.



There are no brushes in an induction motor.


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## caseyvand (Jun 16, 2014)

I was not able to use a VFD because my Bridgeport motor was 550 Volts 3 phase. I opted to use a DC  motor, electronic board, and pot switch from a treadmill and this worked satisfactorily for me. This set up gives me adequate power, variable speed, low noise and forward and reverse .It's not pretty but works for me.


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