What's new
What's new

115V vs 230V VFD for SB 10K

HunterL

Plastic
Joined
Dec 17, 2018
Hello,

This is my first post. I just purchased a South Bend 10k lathe and the previous owner installed a new motor in it. He installed a 230V, 1.5HP, 3-phase motor. The part number is a Baldor BM3554 https://www.baldor.com/catalog/BM3554.

I want to buy a VFD to run it in my home, but I don't have 230V outlets in my shop. Should I try and find a 1.5HP VFD that can operate off 115V? (I haven't been able to find any reasonably priced) Should I just run 230V to my shop? Or should I get a 115V 1HP VFD? I don't need the full 1.5HP, I believe the lathe originally had something like a 1/2HP motor anyway.

Last question, does using a larger motor (1.5HP vs original 0.5HP)run any risk of damaging the lathe?

Thanks!
-Hunter

00v0v_2o8N4IVkxxb_600x450.jpg
IMG_20190129_073750194.jpg
 
The technology that allows a 120V input to feed a 240V VFD, called a "voltage doubler", becomes prohibitively expensive once you get above a certain amperage, which equates to 1HP at 230V. That's why you can't find them. But what you can do instead is to get a (lower cost) 240V single phase input drive and just buy a cheap transformer to put in front of it that boosts your 120V to 240V. For a 1-1/2HP 3 phase motor, around 6A FLC, you will need a 3kVA transformer to feed that drive.
 
First, you will never be able to use more than 3/4 hp without the belt slipping. The belt is the mechanical fuse on that lathe. Using a 3 phase motor on that lathe is very important because it allows a much better finish on very fine cuts. (long story) Moving 230V into the area is very inexpensive. That is the best way to go.
 
There are a few VFDs that will run off of 115VAC and provide 230VAC for a 1.5Hp motor, you might check with the vendor below as to availability of those two models. Problem will be that you will most likely need a 30A 120VAC breaker and associated wiring, and as you noted the VFD's can be stupidly expensive. Running a 1.5 Hp motor with a 1.0Hp VFD it will most likely go into a fault mode on acceleration, and may fault while turning. Your best bet is to wire in a 230VAC circuit and get a 1.5Hp VFD 230VAC input OR you can get a 1.0 Hp 3 phase motor and a 115V 1.0 Hp VFD which are common and much less expensive. I would recommend getting 230VAC circuit unless prohibitively expensive, otherwise switch out the motor.

https://dealerselectric.com/VACON0020-1L-0005-1-R02.asp
https://dealerselectric.com/DRIVE-T205.asp

As far as the belt slipping, it depends on a lot of factors. Often you are using the motor below it's base speed so at 30Hz you would have only 0.75 Hp. One reason why motors on lathes are often up sized when used with a VFD. Most VFD's offer braking but for quick braking you need one that supports an external breaking resistor. If you have a screw on chuck with out a lock, the chuck can spin off if you brake too quickly. You are also limited by the belt drive used in that lathe.
 
Ok great! Thanks for all of the extremely helpful information. I'm just going to get a 230V VFD and wire my shop for 230V.

I notice that dealers electric sells 1.5Hp motor/vfd combinations for around $280 (https://dealerselectric.com/Package-NAT1-5-18-56-and-L510-202-H1-U.asp), but when I google just the motor on my lathe I see it costs around $900. BM3554 - Baldor.com
EBM3554Y BALDOR 1.5HP BRAKE MOTOR 35A022M493G2

What is the deal with this price difference? Also I see that the BM3554 motor on my lathe is a brake motor. What does this mean, and is there any problem using a brakemotor on my lathe?

Lastly, dealers electric has a 2Hp VFD for cheaper than any 1.5Hp VFD. There's no downside to getting the 2Hp for my motor right? Which of the VFDs below would you reccomend?

WEG, CFW500A04P3S2NBN1, 1.5 HP, Variable Frequency Drive 230 Volt, 1 Phase Input, NEMA 1, at Dealers Industrial
Teco-Westinghouse, L510-202-H1, 2 HP, Variable Frequency Drive 230 Volt, 1 Phase Input, IP20, at Dea

Thanks again for all the help!
-Hunter
 
Looks as though the new limit is 1-1/2HP now...
Most likely the component cost came down.

But one of the other reasons for the 1HP limit was the fact that 1HP is pretty much the limit of what you can run on a 20A 120V circuit run with 12ga wire, which a common size, so you MUST make sure that your circuit can handle the higher amps at 120V.

A 1-1/2HP 230V 3 phase motor will be somewhere around 6.8A FLC, which at single phase 230V input would be 11.8A so at 120V input would be 23.6A, which would require a 30A 120V circuit and #10 wire.
 
One caution on the first of the two drives linked in message #5, above- the Danfoss drive (I generally hold their products in very high esteem) contains reference in the description that it is especially well suited for "pumps and fans" which tends to strongly suggest that it is a variable torque drive, which is much less well suited to a machine tool application - see some of the description here
What is the difference between Variable Torque and Constant Torque for AC Drive ratings?

The KB Electronics 27D has the ability to run on 115V supply and operate up to a 2HP motor
http://acim.nidec.com/drives/kbelec...cuments/ac-drives/data-sheets/kbac.ashx?la=en
it's not cheap but it does have the advantage of being in a good sealed enclosure and has the speed and switch controls right on the outer housing.

If you have a spot to mount a drive out of the way of swarf and spattered coolant or oil, but with adequate air for cooling, the KBVF 26D is a nice unit at substantially lower cost, and you can piggyback onto it with the "MSB Multi Speed Board 9503" that gives you the ability to set up to four preset speeds and directions that can be controlled with very simple switching https://www.kbelectronics.com/data_sheets/9503.pdf

That Baldor is a very good quality motor and if it is in good condition and if it were me I'd just stick with it and maybe set the current limits in whatever drive you choose to levels that won't strain your 120v source.

Just some possibilities. Good luck and let us know what you decide on, and how it works. I have a 10K that I need to go through and clean out/clean up and I am going to run a 1HP with a KBVF24 drive with the preset board.
 
The Danfooss VACON® 20 AC drive will do constant torque or variable torque, it is also sensorless vector.

The motor you have is fine, it is a good motor, just remove the mechanical braking unit on the end. It is probably just what someone had and stuck on the lathe. It doesn't sound like the electro-mechanical brake was being used, would be pretty unusual in this application. I have removed the mechanical brake on a number of these types of motors when they were switched over to VFDs and subsequently used electronic braking. Please be aware that the motor is rated at FLA of 5.0A at 230VAC, so some 1.5 Hp VFDs cannot supply this level of current. So best to go with a 2 Hp VFD which typically have a rating of around 7A, check the VFD output ratings and give yourself a little margin.

I typically do not recommend the L510 for lathes because of the limited number of inputs/programming and it does not support an external braking resistor often needed in this application. The E510-202-H-U would be a better choice Purchase 2 HP VFD, 230 Volts, NEMA 1/IP20, Teco, E510-202-H-U at Dealers Industrial

The 1.5 Hp WEG you linked to although rated for 1.5 Hp is only rated for 4.3A output, so you would need the 2 Hp WEG which is rated for 7A, or a different 1.5 Hp rated for higher amps.
https://dealerselectric.com/CFW300A06P0S2NB20.asp
WEG, CFW500A07P0S2NBN1, 2 HP, Variable Frequency Drive 230 Volt, 1 Phase Input, NEMA 1, at Dealers Industrial

I am unfamiliar with the WEG VFDs, I would be more inclined to go with the Teco E510 as they seem to be a bit more user friendly. They also allow you to remotely relocated the control panel on the NEMA 1 models. I primarily use Hitachi WJ200 and the Yaskawa V1000 in smaller mills and lathes, but they are more pricey and the manuals can be challenging for new users.

I have installed/used a number of KB VFDs, I find them very limited as to function, inputs and programming. They brake poorly and often the external braking module is proprietary and cost almost as much as the VFD. They are expensive. OK for grinders and stand alone, but these days I would use a NEMA 4 E510 instead of the KB VFDs.
 
Ok, thanks for the advice. I've already ordered the L510 and it should be arriving shortly. Perhaps I should talk to dealer's electric and see if I could return it for the E510 or another VFD with braking resistor option.

My lathe has a thread on chuck, so will it be safe to use the breaking resistor? I don't know if it would stop the lathe too fast and risk it unthreading.
 
If you do not have a chuck lock, then you would not want it to brake too quickly. The L510 will probably work OK otherwise. Just doesn't work well if you need quicker stops which are desirable when threading/feeding to a stop position. Some people add a set screw, locking pin or split collar to prevent the chuck from spinning off. You can do a search in this forum or Google for what others have done.
 








 
Back
Top