# Single Phase to Three Phase Options



## wareagle (Dec 12, 2007)

We, being the home shop machinist, sometimes have three phase equipment in our shops that we would like to run. Being a "home shop", we typically have single phase power. That presents a problem for us, but there are options.

The first is to change the motor for a single phase motor. This can be a bear as the frame sizes between motors are totally different, and there is usually considerable work needed to mate the new motor up to the existing mounting configuration. The motors can be expensive as well if you are buying a new one.

The second option we have is to install a static phase converter. They work well, but have some drawbacks. The motor is only good for 2/3 of the rating, so if you have a 3HP motor, you are effectively getting 2HP out of it on a static converter. For our needs, this probably will do just fine. They range in price, but for a 1-3HP model, they run about $125.00.






The third option is to install a rotary phase converter. This is a better option from the stand point of you are getting the full rating out of the motor rather than just two thirds. However, they come with a price tag. A 3HP model runs about $550.00.





The fourth option is to get a VFD (Variable Frequency Drive) that has a built in phase converter. These unit have an advantage over the above option in that you can adjust the speed of the motor with the drive, yet retain the rating of the motor (to a certain degree). This is an attractive option due to the cost versus flexibility of the unit. One of these VFD units for a 3HP motor will run about $195.00.





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There is a story behind all of this, so here we go. I rescued a 10x50 mill from a business several years back. I won't get into details in this post, but the electrics were shot, and it needed some TLC. It has a three phase 3HP motor on it, and I had to have an option of powering it up in the home shop environment. I took the cheap road and bought a static phase converter. It worked fine. The mill ran great, and life was good. Except for one thing. When the motor was cold, it had a hard time starting. If it were cold enough, it wouldn't turn the motor over to start without some human assistance. Still, it was a workable situation, and after running the motor for a couple of minutes, it was good to go.

Somewhere along the way, I heard of the VFDs with the built in phase converters. So, I looked into them, and found they were fairly inexpensive. I bit. The thought was that I would put in on the milling machine to see if there would be a benefit. It came in, and I installed it in a temporary fashion. Upon initial power up and a little bit of program setup, I cranked up the mill and played with it some. Well, I played with it for about a minute. That was all it took. I immediately made the installation permanent, and ordered a remote speed dial for it as well. The following week, everything was here and installed, and I now had a mill with a spindle that has infinite speed control from about 4 RPM to a little over 5000 RPM.

Once this mod was done, it made it a totally different machine! With the fine speed control, finishes were better, the power is better, and there aren't any pesky belt adjustments needed for typical machining operations. And the cold motor troubles are history. Looking back, if I had it to do over again, the VFD would be the way I would convert the power. In my opinion, the flexibility of the speed control coupled with the relatively low cost is hard to beat!


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## cfellows (Dec 12, 2007)

I saw one of these demo'd at NAMES a number of years ago. They were closer to $400 back then, but this was probably 6 or 7 years ago!

They really are slick. Unlike DC motors with variac's or Pulse Width Modulation, the VFD three phase powered motors have full torque down to the lowest speed or so I understand. 

The only downside, again, so I've heard, is that the motor might overheat if run continuously under a heavy load at too slow an RPM for the built in fan to properly cool the motor. 

All in all, I've thought about putting one on my old logan lathe many times. May be time to investigate them again with the price as low as it is.

Chuck


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## 1Kenny (Dec 12, 2007)

I have often wondered about the VFDs. Are the instructions with them easy to understand?

Kenny


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## wareagle (Dec 12, 2007)

The instructions with mine were fairly easy. Keep in mind that my vocation is in the electrical industry, so there may be an unfair judgement on that, but programming was easy, and the connections were straight forward. A little bit of study on the different features will be required to get the program setup to your liking. 

Here are the instructions for the unit I have. There are other models and brands out there as well.

http://factorymation.info/acdrives/FM50manual.pdf


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## shred (Dec 13, 2007)

I dunno.. I have a FM50 as well, and the manual is pretty obtuse to me. The good thing is you pretty much only have to set a few settings and you're off and running. I have one running my T&C grinder-- it converts 110 to 220 as well as making it 3-phase, which rocks.


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## Seanol (Dec 13, 2007)

Guys,
I currently have a VFD on my 3hp Takang 105 13x40 lathe. Yes it is nice for speed control but it does not remove the need for gear changes (or belts) as low end torque suffers. I can stop the spindle with my hand when the lathe is in the highest gear.

When it is really cold (here in the North East in an unheated garage) it has a very hard time getting to the 2 highest speeds due to cold oil. After a warm up it is fine. A better drive would be a vector less VFD drive. They have full torque at low rpm's. They are more expensive, but not inordinately.

Just passing on my experience only, not an expert, stayed at a Holiday Inn Express, ....

Sean


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## wareagle (Dec 13, 2007)

Seanol  said:
			
		

> Guys,
> I currently have a VFD on my 3hp Takang 105 13x40 lathe. Yes it is nice for speed control but it does not remove the need for gear changes (or belts) as low end torque suffers. I can stop the spindle with my hand when the lathe is in the highest gear.
> 
> When it is really cold (here in the North East in an unheated garage) it has a very hard time getting to the 2 highest speeds due to cold oil. After a warm up it is fine. A better drive would be a vector less VFD drive. They have full torque at low rpm's. They are more expensive, but not inordinately.
> ...



You are correct in that a normal VFD will not deliver full torque at the low speeds. You are also correct in the fact that a vector drive will keep full horsepower (not really, but close) throughout the speed range. However, the motor you put a vector drive may not have a long life span if it is cheaply built motor. The manufacturers say you don't need a special motor, and you really don't, but the lower cost motors just don't have the beef in them to take the heat. Last time I checked, a vector drive for a 3HP motor was in the $1000 range (they may be cheaper now as it has been a couple of years since I priced one that small). This, in my opinion, puts the technology out of the reach of the typical hobbyist.

For our "non-production" shops, the everyday VFD will do just about everything we ask of it.


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## Hilmar (Dec 13, 2007)

Hi Guys

TECO 230 VAC single PH in  3 HP 3 PH out: $311.00

115 AC single PH in 3 PH out  1 HP  $99.00
 I use one on my 9X20 Lathe for a year now best thing there is. Forget the DC. 
With this on You never look back.
Hilmar


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## Seanol (Dec 14, 2007)

Wareagle,
Thanks for the clarification. My lathe has an old 3 phase motor on it so I don't know how it will hold up with a vectorless drive. When I was looking they were in the $300 to $500 dollar range.

While it may seem that the equipment I have is more industrial, I do work as an HSM'er. I decided that a used older lathe was a better compromise for the various things I wanted to complete. I am a firm believer in putting the money in my tools as the return is better. This does not preclude China as I have a 6x26 Grizzly Mill as well.

If you ask my wife, she will never call it a production shop, she never sees anything out of it but Bills!javascript:void(0);

Respectfully,
Sean


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## wareagle (Dec 15, 2007)

Seanol  said:
			
		

> Wareagle,
> Thanks for the clarification. My lathe has an old 3 phase motor on it so I don't know how it will hold up with a vectorless drive. When I was looking they were in the $300 to $500 dollar range.
> 
> While it may seem that the equipment I have is more industrial, I do work as an HSM'er. I decided that a used older lathe was a better compromise for the various things I wanted to complete. I am a firm believer in putting the money in my tools as the return is better. This does not preclude China as I have a 6x26 Grizzly Mill as well.
> ...



*Seanol*, your motor should hold up just fine with a vectorless drive. The cheaper chicom type motors aren't as beefy in the windings as the American counterparts, and they just don't take the heat (or abuse) that the better built motors can take. If you are looking at installing a drive, then don't let the motor stop you. It is really hard to say that that particular motor you have will cook itself with a drive. If it does, get a replacement. If it doesn't, then that's even better! So many variables are present with usage styles, ambient temperatures, loads, voltage variables, and anything else under the sun that who knows if the motor will last or not.

If it were me and I was looking to put a drive on a "cheap" motor, I would install it and run it. If the motor lives, then great. If the motor dies, then get another one to replace it or have it rewound. A side note, the motor on my lathe is a "cheap" single phase motor, and if/when it decides to give up, I will most likely install a three phase motor in it's place with a drive to increase the options with the lathe.

NOTE: This is in no way saying that the "cheap" motors aren't any good and everyone should replace them with good old high quality stuff, nor am I trying to bash someone's equipment. Please don't interpret the statements this way! It is just stating that if a drive were installed and the motor being driven isn't happy with the heat it may shorten the life span of the motor.


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## dparker (Dec 21, 2007)

Hello All: Merry Christmas to all in a few days! I have a question. I have my Dad's 14/30 2 HP lathe (1977 Jet knockoff I think) which is a 3 phase and was used in a 3 phase shop, I had to move it out when Dad passed away and when I get it set up again it will be in a single phase shop. I ran a Test Lab (medically retired now) for a pump company and used a 500HP VFD, but we were not to shut down the equipment unless we used the VFD which utilized the ramp down option. This was to protect the VFD panel from a voltage spike when the motor was disconnected. We had pendants that allowed us to have ON/OFF control switch near the test setups, OSHA wanted "local" controls. Now back to the lathe, it has a on/off button and foot brake that stops the motor instantly (or almost). Will a small VFD have any spike protection if I decide to use the foot brake or turn the power switch to the off position rather than shut it down with the controls on the VFD? There is also a wood planer that is 3HP, 3 phase that I could use with the same VFD, same question , a on/off switch is at the planer. Panic shutdowns are not wanted but are sometimes a must in real life. Are the new VFD units protected for these situations? 
I would welcome any comments about how to set this up for use when I get the chance to build the shop and play with the larger lathe and other equipment.
Thank You ---Don


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## wareagle (Dec 21, 2007)

You can get a module that will protect the VFD from a voltage spike from a rapid siconnect on the motor. Also note that VFDs typically have an emergency circuit built into them. For the lathe (and saw), if it were me doing it, I would use the VFD to operate the motor exclusively. The VFD can be set up to have braking on the motor which can be a very nice feature as it can slow down the motor faster than a power off stop.

Have a Merry Christmas!


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