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Discussion Starter #1
I want to put a VFD and 3-phase motor on one of my small lathes. I have a 12" craftsman that doesn't currently have a reversing motor on it, which I could really use for some projects I have in mind. It's only a 1/2 HP motor and after looking at what a decent used motor will run on ebay, I can get a cheaper 3-phase motor and a VFD for maybe $50 more, and that'll open up all the little extras a VFD can give me.

Googling and reading other sites doesn't have me any less confused.

What exactly do I need to look for in a motor and/or VFD as far a sizing, voltage, wiring etc.? i.e.: Do is there any de-rating on the motor's power - like do I need to go to a 3/4 hp to keep the same power my single phase 1/2hp has?

I found some dayton motors on the 'bay that are cheap and would be direct bolt-in replacements, but I want to be sure I'm not missing something...




Any recommendations for a decent, cheap VFD.
 

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Discussion Starter #2
Another thought -

Current motor is (and lathe is designed around) a ~1700 rpm motor. Any benefitor drawback to going with a 3400 rpm motor and using the VFD to slow it down? Theoretically I could eliminate the need for the step pulleys, at least between the motor and countershaft.
 

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For motor horsepower, it's motor horsepower. I don't think you need to de-rate a motor, ie 3/4hp 3ph motor != 1/2hp 1ph motor. Whether you want to put a 3/4hp motor in to replace a 1/2hp motor is up to you if your lathe can handle it.

For VFDs, "they say" you need to de-rate the VFD for driving a 3 phase motor. This means if you're going to drive a 3/4hp 3ph motor, you should do it with a 1hp or 1.5hp VFD. Details below, but my first VFD setup drives a 1hp motor with a 1hp VFD and I've had no issues.

For the RPM, if the power the motor puts out changes with RPM, and I believe electric motors put out less HP when they're running slower than their rated speed. You'd need to research this some more.

IMO, if you're taking a 1/2hp 1ph motor out, put a 3/4hp or 1hp 3ph motor in with a 3/4 or 1hp VFD to drive it.

EDIT:
I have a TECO westinghouse VFD driving a set of big fans in my garage. I'm very happy with the quality and price. I would recommend it to anyone. They make different sizes with different inputs, but I'm using a 1ph 110v input, 220v 3ph output L510 to drive my 1hp fan motor.

Video explaining my setup:
https://www.youtube.com/watch?v=-P67RK7iDsE

Amazon link to the VFD in the video.
https://smile.amazon.com/Teco-Variable-Frequency-L510-101-H1-Inverter/dp/B01J8K3UVI/
 

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I'm running a 2HP-rated TECO L510 on my 2HP 3-phase grinder. Works like a champ. I have been able to overload it, but only in a specific circumstance--my drive is set up to provide some braking when you shut off the grinder. If it's at a certain part of the braking cycle, it's apparently pulling some juice. Turning it back on at a certain rpm will put the drive into overload, and I have to cut power to it to reset it.

So, not a real problem, and could possibly be completely removed if I turned off the braking feature. I don't, however, have any idea if I'm actually putting out 2hp.

Edit: Looks like I have the same drive as GLTH3984398. I've been very happy with the features, too. The manual (very strangely) doesn't actually show them all, but a google search will find it's a very well-known model. And I think a lot of the forums with info about it were machinist-type forums.
 

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Motor is sized based on the load. If you only need 1/2hp for the lathe, then keep a 1/2hp motor.

The VFD, unless it's 1ph input rated will need to be derated by 42.2% IIRC. Too much amperage on only two of the input legs to power the same output on 3 legs is bad unless the VFD is built to support it. 1/2hp 3ph motor, 1hp VFD.

Plenty of fractional VFD's out there rated for 1ph input though that do not need to be derated.

Don't try and lug a 2 pole motor in place of a 4 pole. The curve and lack of fan speed will cook it. You can over speed a 4 pole with a VFD to 200% of it's rated rpm (1750) but you loose a lot of torque doing so (down to 30% IIRC).
 

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With regards to de-rating, I hunted forever for a big VFD and found that to get my mill to run (bridgeport) I was going to have to spend $1000+ on a VFD..

Turns out, that a lot of VFDs are de-rated right on the plaque.

Example: If it says:
Input:
220V 3Ph 20A

or

220V 1Ph 10A

You don't need to re-de-rate the 220V 1Ph 10A down again to 5.
 

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Discussion Starter #7
Holy shit, I just noticed how bad I botched that thread title :laughing:

So it sounds like I'll be ok going with the 1/2 HP like above. No need to go bigger since this lathe just slips the belts when you get too much load on the spindle.


I like the looks of those Tecos, except I was hoping for something with a detachable face. It's not going to be the best setup if I need to mount the entire box within reach of the machine.

But, a quick scan through the manual and it looks like they support external inputs so I could make a little control box with start/stop and jog buttons and a stat for speed control. Might just work.
 

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So is the goal to use a VFD to use single phase on a 3 phase motor?

NOT ALL VFD’s can do that.

I have a VFD on my lathe, to use it in single phase, but it sure wasn’t $50.00

I’d look at www.automationdirect.com or give them a call. They’ll help you select and size it if you want them to.
 

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I'm running the TECO VFD off remote stop and start buttons. I didn't mess with a remote rotary dial for speed, but it definitely supports that. Don't know about jog functionality.
 

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Discussion Starter #10
So is the goal to use a VFD to use single phase on a 3 phase motor?

NOT ALL VFD’s can do that.

I have a VFD on my lathe, to use it in single phase, but it sure wasn’t $50.00

I’d look at www.automationdirect.com or give them a call. They’ll help you select and size it if you want them to.

That'a generally the goal of the average home shop user when they install a VFD. Even the cheap chinese ones on ebay will do single in and three out - but they're pass through voltage so you put 220 in, you get 220 out. You can get those for ~$70.

The TECO one someone posted above says right in the specs "115V 1-Phase Input, 230V 3-Phase Output". I still don't know enough about 3-phase, but I'm assuming the voltage is adjustable too since the motor I'm buying is rated at 208-220 or 440.


If you look at automation direct's GS1 line, you can get a 1/2 HP single to three phase drive for $117.

They were actually one of the vendors I couldn't think of yesterday. They've sponsored a few of the youtube shop guys and there are a couple build/reviews on them. I want to say they're just chinese drives but they come with better documentation and support.


I'm running the TECO VFD off remote stop and start buttons. I didn't mess with a remote rotary dial for speed, but it definitely supports that. Don't know about jog functionality.
https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf

Page 116, looks like it's as easy a connecting a 0-5k pot between 10v, AVI and ground.

Jog looks just as easy - 12v with a momentary switch to S4/S5 for forward/reverse.
 

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I dunno what a 3 phase motor and VFD will run cost wise, but you can get a DC motor and motor controller for around $250 plus shipping...

1/2 HP 90 Volt DC Motor | DC Motors Face Mount | DC Motors | Electrical | www.surpluscenter.com

90/180 Volt DC Variable Speed Control w/Potentiometer | Motor Speed Controllers | DC Motors | Electric Motors | www.surpluscenter.com

Another option to think about anyhow. Variable speed with a potentiometer and easy motor reversing with a double pole double throw switch to swap the two motor leads around.
 

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That'a generally the goal of the average home shop user when they install a VFD. Even the cheap chinese ones on ebay will do single in and three out - but they're pass through voltage so you put 220 in, you get 220 out. You can get those for ~$70.

The TECO one someone posted above says right in the specs "115V 1-Phase Input, 230V 3-Phase Output". I still don't know enough about 3-phase, but I'm assuming the voltage is adjustable too since the motor I'm buying is rated at 208-220 or 440.

If you look at automation direct's GS1 line, you can get a 1/2 HP single to three phase drive for $117.

They were actually one of the vendors I couldn't think of yesterday. They've sponsored a few of the youtube shop guys and there are a couple build/reviews on them. I want to say they're just chinese drives but they come with better documentation and support.

https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf

Page 116, looks like it's as easy a connecting a 0-5k pot between 10v, AVI and ground.

Jog looks just as easy - 12v with a momentary switch to S4/S5 for forward/reverse.
I've got remote controls on my VFD with on/off and a pot for speed control. Very easy.


3 phase has varying voltage, just like single phase:

https://ctlsys.com/support/electrical_service_types_and_voltages/

Three phase motors can often be dual voltage, so depending how they're wired, they can operate on 240 or 460, or higher. Many single phase motors have the same thing. My air compressor is single phase 120v, but can be rewired to run directly off of single phase 240v.
 

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That'a generally the goal of the average home shop user when they install a VFD. Even the cheap chinese ones on ebay will do single in and three out - but they're pass through voltage so you put 220 in, you get 220 out. You can get those for ~$70.

The TECO one someone posted above says right in the specs "115V 1-Phase Input, 230V 3-Phase Output". I still don't know enough about 3-phase, but I'm assuming the voltage is adjustable too since the motor I'm buying is rated at 208-220 or 440.


If you look at automation direct's GS1 line, you can get a 1/2 HP single to three phase drive for $117.

They were actually one of the vendors I couldn't think of yesterday. They've sponsored a few of the youtube shop guys and there are a couple build/reviews on them. I want to say they're just chinese drives but they come with better documentation and support.




https://www.tecowestinghouse.com/Manuals/L510_instruction_manual.pdf

Page 116, looks like it's as easy a connecting a 0-5k pot between 10v, AVI and ground.

Jog looks just as easy - 12v with a momentary switch to S4/S5 for forward/reverse.
Drives are sold in two classes mainly, 200v and 400v. You can't output 480v on a 200v class drive except for the super pricey ones. They're usually -10%/+20% rated.

You can set a drive to constant torque where it does just adjust voltage in the range, while maintaining the current output, as opposed to ramping current with constant voltage. You can set the output voltage for whatever you like in the range, 208, 230, 240, 211, etc.

As long as the drive has external inputs, remote switching, pot's and triggers it's easy. It's what they're designed for, to be integrated with a plc and process sensors or put on a network.
 

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I just finished the install of a 1.5hp 3ph motor and VFD on my HF knee mill. Probably the best thing I have done with it as far as conversions go. I can run from 200 rpm to 2200 rpm by turning the pot meter on the remote panel. I was also able to hook up a fwd-off-rev switch for standard operation and another momentary for jog. Jumping belts will get the RPM down to 20 RPM. I'm not really sure how fast I can get spindle RPM as I haven't need to go faster than 2200 rpm.

One thing I might suggest is also installing a hall effect Tachometer. If you use a VFD you will really not know what RPM you are turning without it or a hand held tach. This seems to be a lot more forgiving on a lathe than a mill but without this function on the mill I would lose a lot of HSS end mills before I got to know what frequency = a given RPM. The VFD I used has a 12V output that powers the hall effect tach so installation was very simple.

I used a Baldor motor wired for 220V 3 phase from CL for $50.00 and I had less that $100.00 into the VFD from China. The directions suck so it took a while to figure everything out. I am not an electrician and I was able to figure it all out without letting the smoke out, so it's not that bad.

I know you probably already know this but be very careful reversing your lathe with a thread on chuck. You can end up with your hands full very quick. If it is a cam type reversing is the poop! I do all my parting, a lot of threading and boring bar operations in reverse. It is very nice.
 

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I dunno what a 3 phase motor and VFD will run cost wise, but you can get a DC motor and motor controller for around $250 plus shipping...

1/2 HP 90 Volt DC Motor | DC Motors Face Mount | DC Motors | Electrical | www.surpluscenter.com

90/180 Volt DC Variable Speed Control w/Potentiometer | Motor Speed Controllers | DC Motors | Electric Motors | www.surpluscenter.com

Another option to think about anyhow. Variable speed with a potentiometer and easy motor reversing with a double pole double throw switch to swap the two motor leads around.

A friend of mine just gutted and old tread mill, which had a 1.5HP DC motor and controller, to convert his lathe over. Thing works stellar, variable speed, tons of torque, and cheap.
 

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Window Licker
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Discussion Starter #16
I dunno what a 3 phase motor and VFD will run cost wise, but you can get a DC motor and motor controller for around $250 plus shipping...

1/2 HP 90 Volt DC Motor | DC Motors Face Mount | DC Motors | Electrical | www.surpluscenter.com

90/180 Volt DC Variable Speed Control w/Potentiometer | Motor Speed Controllers | DC Motors | Electric Motors | www.surpluscenter.com

Another option to think about anyhow. Variable speed with a potentiometer and easy motor reversing with a double pole double throw switch to swap the two motor leads around.
I scored a motor on ebay for ~$45 last night and the drive will run around $140, so under $200, assuming the motor is good. Pretty much the same price point if you buy a NOS motor on ebay, but I think you get more out of the VFD vs. a DC drive. That DC drive you linked doesn't appear to have any type of reversing (you'd have to wire in a switch in-line with the motor). A VFD gives you programmable reversing, braking along with ramp up/down if you need it.

From what I understand, these consumer VFDs are just inverters that convert single phase AC to DC and then back to 3-phase AC.
 

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Discussion Starter #17 (Edited)
Alright, so bought the 1/2 HP dayton motor that I posted in the first post. $45 shipped on ebay. It was one state over and would have been here today but UPS is apparently afraid of the snow. :laughing:

Ordered an assortment of LED momentary buttons and a latching power button like this from Bangood. - About $3 each + $1 each for the wire harness to go with them. Total: about $12-20 depending how many I use.


Also found a 0-5k pot with a 0-100% ring for $2.60 on Banggood.


I'll need to get a project box of some sort to mount these in.


Now I just need to pick a VFD. I'm stuck between these three:

The Teco 1HP @ $152 https://smile.amazon.com/Teco-Variable-Frequency-L510-101-H1-Inverter/dp/B01J8K3UVI/


The automation direct 1/2HP GS1 @ $117 https://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS1_(120_-z-_230_VAC_V-z-Hz_Control)/GS1_Drive_Units_(120_-z-_230_VAC)/GS1-10P5


Or the Automation Direct 1/2HP GS2 @ $166 https://www.automationdirect.com/adc/Shopping/Catalog/Drives/GS2_(115_-z-_230_-z-_460_-z-_575_VAC_V-z-Hz_Control)/GS2_Drive_Units_(115_-z-_230_-z-_460_-z-_575_VAC)/GS2-10P5


All of them will do what I need and then some. All are 110 single phase to 220 3ph. I'm leaning toward the GS2 becuse it has the removable control panel, which I could mount in the box with the other switches and probably have more functionality. Not sure if that's worth the extra $50 or not. The TECO would be fine and I could get it prime in 2 days, but it's a good bit larger in dimension that the AD ones and it's 1HP where I only need 1/2.


Depending which drive I go with, I'll be in a total cost range of about $180-230.
 

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I'm sure all the VFDs will work fine. I've been very happy with my L510, used it frequently over the summer. Never one hiccup, so that's what I'd recommend.

EDIT: Thanks for the mention about Banggood. Hadn't heard of that before, lots of good cheap electronics equipment there.
 

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Discussion Starter #19
I'm sure all the VFDs will work fine. I've been very happy with my L510, used it frequently over the summer. Never one hiccup, so that's what I'd recommend.

EDIT: Thanks for the mention about Banggood. Hadn't heard of that before, lots of good cheap electronics equipment there.
Yeah, I think it's down to form factor now. I'd really like the remote mount control of the GS2, but I'm not sure it's worth the extra $50. I'll probably go with the GS1 just to keep the costs down. Trick is to mount it somewhere where I can still see the display so I have an idea of what frequency it's running at with the pot.


Banggood is great. I bought a bunch of my carbide tooling for the lathe there and have zero complaints. For about $35 you can get a 7 piece tool set with inserts for less than you pay the same quality single import tool from Enco.

https://www.banggood.com/7pcs-12mm-Shank-Lathe-Turning-Tool-Holder-Boring-Bar-with-7pcs-Carbide-Insert-and-Wrench-p-1110118.html?rmmds=detail-left-hotproducts__2&cur_warehouse=CN
 

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Banggood is great. I bought a bunch of my carbide tooling for the lathe there and have zero complaints. For about $35 you can get a 7 piece tool set with inserts for less than you pay the same quality single import tool from Enco.

https://www.banggood.com/7pcs-12mm-Shank-Lathe-Turning-Tool-Holder-Boring-Bar-with-7pcs-Carbide-Insert-and-Wrench-p-1110118.html?rmmds=detail-left-hotproducts__2&cur_warehouse=CN
I just loaded up on inserts from there and two sets of smaller boring bars as well. Sure can't beat the price!
 
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