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3 phase conversion experts

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Dave H (MI)

Well-known Member
Have the lathe sitting where it goes. That was fun...weighs 1060 lbs. The motor...per literature...is single phase, 2 HP, 1800 RPM, 60 Hz, 230/460v (set up on 230). I am going to use a VFD as it best suits my situation. Not going to make my own converter, not qualified to play with such things. Need help selecting a few things. What size breaker should I buy or is this something specified by the VFD manufacturer? Any recommendations on a make/model VFD? All I know for sure is that it has to be 230 single in and 230 three phase output and able to handle 2 HP. Seems to me I remember somewhere that maybe a motor needs a little extra to start it...anyway...looking for recommendations since I will likely buy on-line and there wont be a salesman around. Any concern about the service coming in? I have plenty of room in the breaker box.
 
Dave,

In an earlier post you stated motor was 3 phase, in this one single phase.

As stated, you do not need VFD if single phase.
 
Is your intent to use the VFD to increase or decrease motor rpm? That nice looking lathe should have all the gearing to do speed changes
without a vfd.

Beagle
 
I assume you meant the motor is 3 phase...

Yes you do have to oversize the VFD. For a 2HP motor, go with a 3 or 5 HP VFD. The VFD will have the breaker size listed.

You will need to either mount the VFD within easy reach, or add remote start/stop and speed control. You must control the motor from the FVD, not from any existing line voltage drum switch or reversing starter. You can use existing starter to send a signal to the VFD start/stop input.

Don't set the stop time too low, it will nuisance trip. It won't jog or hard reverse like a 3 phase motor will.
 
Yes, sorry...3 phase motor. The rest I am not sure I understand. The lathe has a variable speed control and I was just going to use the VFD as an affordable conversion from single to three phase. One of the reasons I selected this particular lathe was that, in addition to the quick change gearbox, you have the dial control that allows "infinite" adjustment of speed up to 2000 RPM. I don't yet know if this is a control on the motor, but if it is do I have to use the VFD and ignore the lathe control? From what you and others have told me before I thought it was OK just to run the lathe off the VFD three phase and use the lathe controls as designed to control speeds. There is a video on the 2557 Logan on you tube that shows the variable control if it helps to clarify what I am saying.
Logan lathe features
 
Most lathes use a "normal" motor so buying a new one in single phase will be close to the same price as a vfd. I'd sure check into motor replacement first.
 
Forgot, the make of the VFD, I've been using Westinghouse, only because they are the best price I've found.

All you need is a basic drive, some have way more bells and whistles, they come with a price, so does a name brand.
 
You can use any mechanical controls on the lathe.

At the 1:28 mark on the video, the on-stop-reverse switch, you can not use that to directly power the motor through the VFD.

The VFD must be hard wired directly to the motor leads.

There will be a start/stop/reverse control on the FVD. You can use that, or there will be provisions to connect the existing start/stop/reverse back to the VFD low voltage terminal strip.

It's not really that difficult, but there are some basic parameters that need to be entered on setup. The instruction walk you through, or customer service will help, I can help. It's just not a "plug and play" component.
 
Safety Notice:

A VFD is not considered safe like a harwired starter is unless it has safe torque off feature.

You should have some form of mechanical disconnect when sticking hands in moving equipment, unless drive has the safe torque off feature.
 
I'm not real familiar with that particular Logan model, but, the speed change is mechanical I would think. Similar to the variable speed employed on a mill head made by several different manufacturers. I have used the Phase-A-Matic static converters for years on all types of machine tools. Easy to wire up, pretty much trouble free in my experience.

The heavy duty one is the best choice.
 
One thing I have not seen mentioned yet is the need for the magnet wire in the motor to be "inverter rated". Most modern motors are, but older ones are not. If the wire is not up to the task the insulation on the motor windings will eventually punch through from the switching transients and you will be replacing the motor or having it rewound.

You can find VFDs in smaller sizes up to 2HP that will run a 2HP motor off of single phase. It must say so in the specifications. I have a 2HP drive on my South Bend lathe with a 2HP motor. It worked great until the insulation punched through. I did not know about inverter rated magnet wire at the time. Lathe is WWII vintage. Now it is a boat anchor. Motor is two speed, hi speed is 825RPM. Replacement motors not available. The old man who rewound motors by hand for the oil fields is long dead, so someday will have to take on that project myself. Mean time I have a Taiwan made single phase motor lathe that does what I need.
 

You'll need to make sure the lathe's motor is wired for 240 volt, if the VFD is powering a set of reversing contactors make sure the overloads are for the proper amperage
 
Can you elaborate on that because at the moment I am shying away from the VFD just because I cannot use my lathe switch. I would likely replace the motor before I would circumvent the lathe controls to accommodate the VFD. Maybe I should reconsider a rotary phase convertor? The goal here is to have the lathe operate at full power and use all of it's original controls. So a static phase convertor with a drop in power after start is not my ideal, but if a rotary will keep it at full power and not require me to rewire the thing or pull the motor...I'm all in.
 
So here is my question...and I only half understand what you are saying. This is a 1970's era lathe/motor. So who knows if it is inverter rated? Is there a way to tell? Would it make a difference if I scrapped the VFD idea and went to a rotary phase convertor? Would one of those have the same effect on the wiring of an older motor?
 
I've never used a static or rotary converter, but yes it will let you use the lathe as it is wired.

As for loss of power, it's very rare to fully load the motor on a lathe. You would have to be doing some serious material hogging to ever get there.

One of the advantages of the rotary converter is the ability to do instant reverse, very handy when tapping. Not sure if the static converter will do that, it takes some serious instant amps capacity to pull that off.

That's another consideration, if converting it to a single phase motor, it will have to stop before reversing.

As for the insulation not standing up to a VFD, I've used many old motors on a VFD, never had a problem. Doesn't mean the potential is not there for damage, it's just not a common problem, especially running it at 60 hz as it is originally intended.

And you can still use the original switch, it would just have to be rewired back through the VFD control circuitry.
 
Dave H (MI), I thought I would share a picture of my three phase converter setup with you. It's about the cheapest way to go, haven't had any problems whatsoever, can use the machines just as you would plugged in to regular power company three phase. Just use a big enough idler motor so that your machine will use only about 75% of the hp rating of idler motor. (7.5hp idler to run 5hp machine). Your breaker will need to be rated for about 25% more amps than the full load amps of the idler motor if I remember right.

My pony motor has it's own switch I can turn on/off right on the motor. Just got lucky that way. I run the pony motor off an extension cord.

Paul

If you were closer I have a motor I would give you to use as an idler. I think it is 10hp, would need at least 60amp breaker to run, I only had 50A available so couldn't use it.
cvphoto40479.jpg
 
A few things if you are going to use a VFD.


First, you need an inverter duty motor. VFD's, especially the cheap ones, will generate a dirty sine wave and harmonics. Inverter duty motors will be built to handle the extra heat this will generate.


Second, locate the VFD close to the motor, real close. A VFD/motor combination can sometimes generate a standing reflected wave. Keeping the wire between the motor and VFD short will help reduce this. If you do have problems, see if you can get the person who sold you the VFD to size a line reactor for this.


Third, get a harmonic filter on the input.


Finally, 2HP single phase motors are not that uncommon. It may be cheaper and fewer headaches to go that route.
 
Good info there. I am not sure I can do the rewire of the switch back thru the vfd. With instruction, yes...but not knowledgable enough to do it on my own. I need to give rotary convertors a second look.
 

Just supply the lathe with the VFD and use the lathe s factory controls .
Use a 5HP VFD on a 2HP motor when converting single phase input to three phase output.
 
(quoted from post at 23:35:56 10/31/19) Good info there. I am not sure I can do the rewire of the switch back thru the vfd. With instruction, yes...but not knowledgable enough to do it on my own. I need to give rotary convertors a second look.
Click to expand...
I agree with this. Once you are making 3 phase, you can get other tools and add them on. I mentioned in your other thread that I run a mill, surface grinder and a band saw all off the same cedarburg.
 
Ebay item 182444957123 I was instructed to not use the machine switch. The VFD is set up for one motor and one motor only. The parameters are set to match each motor / machine and won't work to start different machines. They are cheap and work well just not a whole shop converter like a rotary converter is.
 
Yes but...what is all this in the prior comments about not being able to use all the lathe controls. My original plan, based on what I thought I knew, was to just take the 3 phase output from the VFD right thru the "plug in" cord for the lathe and use all the switches and controls as designed on the lathe itself and ignore any controls the VFD might offer. But unless I am misunderstanding the other posts...no can do.
 
I used a static phase converter. Very simple for my lack of electrical knowledge. 220 in three phase out. You lose some power, but in all my years it hasn't bothered. I use one on my lathe, and wood splitter. Stan
 
After watching the video of the Logan lathe and looking at your first post picture you can drive that lathe with a VFD. Your variable speed is accomplished with a belt drive system. With the VFD you will get full 3 phase power and you will have to start and stop it with the VFD. Just leave the lathe in forward and locate the VFD right on top of the headstock. Set the VFD to 60hz and use your variable speed like normal. Start and stop will be controlled through the VFD but it works really well and won't damage the VFD. If you want to call me tomorrow I'll be glad to send you pictures of my set up and how it works. I might even be able to send you a video of my Bridgeport vertical mill running on the VFD. I left my phone number in a former reply. With a VFD there are about 35 settings that you have to page though to set them up, that's why you cannot run multiple motors with the same VFD. They are not just a device that coverts single phase to three phase, I wish that were the case.
 
Many thanks, but I am looking into rotary units now. I want to be able to use all the lathe controls as they are. Only makes sense...allows me to buy other 3 phase machines if I want them and hook them up to the same unit. I can only use one at a time. Thanks for all your help and that of everyone else...really gave me the tools I needed to make my decision.
 
....Only makes sense........
Click to expand...

Only to folks that have never used a machine that has been converted to a VFD. Variable speed without changing gears or using a variable sheave system. Soft starts/stops and reversals. No parasitic power use like a rotary. No noise like a rotary. Cheaper unless you have lots of machines to run. The 4 VFDs in my shop machines cost me on average about $125 each.

The concern about insulation damage on a motor not rated for inverter use is way overblown. Sure, the possibility exists, but I have never seen it happen despite having been involved with several VFD installs.

I have 4 VFDs running motors in my shop. The oldest motor is from the 30s and has been used a couple times a week for 6+ years with no problems.

A friend has an older 40HP motor on his sawmill running off a 3 phase genset. Put an inverter on that and set up a soft start to not bog the genset down when starting the blade. That has been running for 10 years now with no trouble.

Factory I used to work at added VFDs to several of the exhaust fans used to keep the air clear in the fab shop. Did that so when things were slow or cold outside they could slow down the ventilation or speed it up in summer or things were real busy. Those were up to 15HP and again never had an insulation problem despite running 24 hours by 5-6 days per week. We did have one of those have a bearing go out after a couple years on the VFD. There was some speculation that it may have been related to VFD use, but was never proven. Replaced the bearings and it was still going when I retired.
 
Buy a new 2hp 230 volt single phase motor in the same frame size number and make sure it is in the same 1750-1800 rpm range. Just make sure it is reversible, as any quality motor will be. With the right frame size it should be a bolt in. Check Grainger or Surplus Center or McMaster Carr.

Garry
 

You can set the VFD to just be a 60HZ three phase power supply.
The VFD will supply what ever the lathe or other tools draw up to maximum current rating of the VFD.
 

You can set the VFD to just be a 60HZ three phase power supply.
The VFD will supply what ever the lathe or other tools draw up to maximum current rating of the VFD.
 
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