# Super Basic Question



## wawoodman (Jun 22, 2011)

VFD=variable frequency drive

It can be either 1Ã˜ or 3Ã˜ input. Some low HP models even take 110v 1Ã˜ input, and give you 220v 3Ã˜ output. The big plus is the variable speed control, and all of the parameters that you can apply. (Way more than I can understand!)


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## Pacer (Jun 22, 2011)

Maybe "alternative" is a better description than "replacement" for the use of a VFD. There are what? 4 sources for 3 phase? The electric pole, a rotary phase converter, a static phase converter, and the VFD? - with the VFD seemingly gaining popularity fast, what with lower prices and the wonderful features.

I just got a Teco 1hp VFD for $130, that's about the same price of a static converter.


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## November X-ray (Jun 22, 2011)

VFDs have come a long way in the last 10 years. The first I ever dealt with them was 10 years ago on installed two 3,500 HP motors running Ariel 6JGD Compressors, these VFD units were made by Siemens and cost a million and a half each . Now that they have come down in price enough to be truly affordable for small HP Motors they really make hobby machinery perform in ways that were not practical before. I have a 2HP Hyundai VFD running a 1HP 3 phase motor and a 1-1/2 HP phase (not simultaneously) and never need to change pulleys again. I have infinite speed control from about 8 RPM to well over 2,000 RPM and at the lowest possible speed setting the torque is constant. And the GREAT Thing is all of this is powered by 220 Volt ingle Phase household current!!!


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## November X-ray (Jun 22, 2011)

In my opinion, a VFD and 3 phase motor is a better/easier choice, I have one on my 9 x 20 and love it. I also have a used treadmill I bought with the intent of installing its motor on my 9 x 20 but I am now glad I went with the 3 phase 1HP motor. It bolted right up and I only had to shave a little bit off of the cast iron plate that the idler pulley mounts to. The original pulley fit and the same belt was used, although I no longer use the cog belt and clutch.


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## November X-ray (Jun 22, 2011)

Just make sure you get the correct frame 3 phase motor and also pay attention to where the junction box (peckerhead) is and it should bolt up with no problems. If I remember correctly mine was a frame 56, but I have slept too many nights since I installed it.


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## November X-ray (Jun 23, 2011)

I went and checked my motor frame size and it was a 56C, however my lathe is a 1994 or 95 model and came with a "Made in the USA" Reliant Motor. Depending on when your machine was produced, it may or may not have a metric size mount.

On mine the junction box is 180 degrees opposite of the mounting plate and fit perfectly!


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## HMF (Jun 23, 2011)

Bill,

The VFD allows you to run a 3 phase motor on single phase 220 power. It also gives you variable speed.
It is preferable to changing to a single phase motor.

Check in the downloads section:

http://hobby-machinist.com/index.php?action=downloads;sa=view;down=131
http://hobby-machinist.com/index.php?action=downloads;sa=view;down=107
http://hobby-machinist.com/index.php?action=downloads;sa=view;down=108
http://hobby-machinist.com/index.php?action=downloads;sa=view;down=102

There are various files on setting up a VFD there, specific to a SB lathe, but usuable on others too.

Best,


Nelson


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## Calpoly93 (Jun 14, 2014)

I know this thread is old, but I stumbled on it during a search...  I am brand new to machining, having inherited an Atlas lathe and tooling.  From what I am piecing together, I could buy one of these VFD motors instead of trying to replace belt pulleys my uncle got rid of. Specifically, the top two of the three inside the cabinet of me 12' Atlas 3996.
Is that correct?

I do have 220v in the garage, and an outlet right next to the lathe spot...

Thanks,
Steve


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## Tony Wells (Jun 14, 2014)

Steve, if I understand your question accurately, yes. There usually is no real need to change gears or belt positions on step pulleys, as long as they stay within the operational parameters of the other rotating components. For instance, a plain bearing machine was designed and built long before anyone needed a 3,000 rpm spindle.....and it would not last long. Or possibly, if the only pulley you have that is usable is a low range, perhaps you could not achieve a high enough spindle speed, although that would be more a matter of convenience than harm to you or the machine. And some sacrifice in surface finish quality possibly. 

Do you have an idea of what the spindle speed would be as the machine is set up now?


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## Calpoly93 (Jun 14, 2014)

Hi Tony, 

Yes, that was the gist of my question.  I know my uncle had put in many homemade parts, and I think he generally used it at a low(er) speed.  I don't know the spindle speed...  He exclusively worked on aluminum as far as I know, to build telescope parts for his home use.  As you can see from the photos, the pulleys are not original. The motor looks to be not original either.  So before I go hunting down the correct pulleys or have them made, I thought I'd look into the VFD option.


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## Tony Wells (Jun 14, 2014)

That setup looks like a good one for a VFD. Look at the motor speed and determine what pulleys would give you your desired top end spindle speed at that motor rpm, then add the VFD to control it, leaving that as the 60hz speed. VFD will exceed 60hz, but it's no good practice, in my opinion. Lower frequencies will yield lower rpm; that's how they work. The only limit on lower speed is then the actual cooling fan speed on the motor. If you can't get low enough spindle speed with that pulley calculation, change it, but just don't plan on using it at above 60hz.

Other opinions welcome.


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