Magic smoke came out of the motor. New IR motor or VFD?

Well I've spent the last few years restoring a 1940s SB 9". Converted from a B to A, new paint, felts, ect. Last thing to do was get the motor spinning. It wasn't wired when I got the lathe, so it was a complete mystery. GE KC 1/4hp motor. Looks identical to the one in Paula's thread. I couldn't figure out what the heck was wire where. The metal tags wertill on the leads, so I used Paula's wiring diagram. Well there was a hiss, pop, and the magic smoke apears to have left the motor. Breaker popped. I'm pretty fed up. I've never used a lathe and figured this would be fun to learn on. I've spent a small fortune on parts and accessories already. I just want to make this thing spin.

So the question is, what can I get for a new motor that won't require a guessing game to wire up. I've seen a few people go with a 3ph and VFD. surfing Ebay, it looks like $2-250 for a VFD and $100-175 for a 3/4hp motor or $200-300 for anew IR motor (1/2 to 1hp).

Tojan,were it me,I would go the three phase route and VFD. On almost every 3 phase motor i've wired up over the years the wiring diagram has been clearly marked on the case or inside the j box. On the few that were not,I was able to do an internet search and find the correct info fairly quickly. The benefit of the three phase route is infinitely variable speed and a bit more power. A call to a local motor rewinder/repair facility if you have one close could net you a used working motor reasonably,and a new VFD that has single phase 240 volts in and three phase out can be had for under $200. ( factorymation.com ) or wolfautomation are 2 companies that I have dealt with that have good prices and quick service,(I just put a TECO drive on my heavy 10). Hope this helps. Jim

I would add that a ¼hp motor is way undersized for an SB 9" lathe. A ¾hp 3 phase motor with a VFD will make you far happier once you get to using it.

A 1/2 to 3/4hp 3ph would be the best option for the lathe. 3ph motors are just smoother than the 1ph and with the VFD your low end torque will be great. Now from where you stand, if you can find a cheap single phase motor local to you this would be a good way to get running and find out where your at with your rebuild, and what else you may need. Local motor shops may have some used motors cheap in either single or three phase. Of course this all depends on the budget, but having and running a lathe will always be eating at your budget, it never ends.


One setup I have used on smaller machines is a treadmill motor and controller. I have picked up two of these off the side of the road where people where throwing them out. D/C motor with VS controller that mounts up easy and its cheap. They don't really have the power you need and are not high quality, but free and easy to work with. All though most of them are rated at 1 1/2 to 2hp they just don't seem to have great low end torque. With warm weather here this is when I find people throw these out.


It can be frustrating to get a machine up and running to a point of being productive. Then when your just starting out you find you need many supporting tools to really be able to make parts. In the end its well worth it and you just have to remember it takes time, plus it will always have a learning curve. Keeping a eye on your local Criagslist will help you find the many supporting tools you need at a good price. In fact I am always finding people that are trying to sale there families shop equipment that may have passed on or be unable to use them anymore. If there reasonable most of the time you can pick up a package deal that really helps kick start your shops needs for a fair price. The reason I bring this up is most of the time it will be these supporting tools/needs that really cost more than the machines you buy. So, keep this in mind when making your choices on a motor, because like I said, it never ends. The main thing is to get running at this point, you can always upgrade latter to what fits your needs best.


Jess

BTW I live in Bristol TN. IDK how close that is to you , if so let me know I might be able to help. I do have some motors, but at this point have not really wanted to get rid of them, but who knows.

3 phase and a VFD would be perfect for a small SB. You need a larger motor, though - probably 3/4 HP would work well. Before you spring for a new motor, check Craig's list or E Bay -- both will have small motors fairly often. Be careful what it weighs if you have to ship a motor - the general rule I've been using lately is about $ 1 per pound.

I agree that 1/4HP is too small but it will run a 9" for light work.

Also just because the motor smoked and popped the breaker doesn't mean it's FUBARed.
With some pictures of the motor and wiring we maybe able help you get it up and running until you get a more suitable motor.

Ken

http://www.practicalmachinist.com/vb/transformers-phase-converters-vfd/new-teco-vfd-install-enclosure-3-ph-motor-226569/

Here is the link to my install.
The Baldor 3/4 hp motor and the Tec Vfd have been perfect in use.

Well I appreciate all the great input. I'm going to do it. VFD and 3ph motor. Yes, there is a possibility that old one isn't toast, but as said, it's underpowered.
What do you guys think of this motor and VFD?

Baldor Electric Motor 3 4HP Cat M3542 56 Frame 208 230 460 | eBay

1 HP 1PH 230V VFD Teco Westinghouse Variable Frequency Drive N3 201 CS | eBay

or should I spend the extra $40 and get the 2hp VFD?
I like this model because it looks like I just need and extension cord and I can remote mount the display/control.

See if this unit has a cable for remoteing the keypad, then you can mount the VFD away from the lathe and have all the controls mounted where you can get at them easily,no extra switches required. I just did the same thing using a TECO 7300 CV, see my post "10L VFD remote control" . I have a 3/4 hp motor with a 1 hp drive,as long as you have a margin of error with the full load amp capacity of the drive (higher than the fla of the motor) the added expense of a 2 hp drive is really not necessary. Jim

I just finished the same with my 9a. I used the stock forward/reverse switch to input to the Teco VFD forward and reverse. I also put in a potentiometer to give the speed control. It works VERY well.

I've been thinking about using the modbus interface to combine with linear encoders for a combined control panel. I really like this setup... Lathe DRO and Speed Controller

Just for argument, if you had a smaller lathe, let's say either a 6" Derbyshire 750, or a 7.5"? Sloan and Chace split bed, what about a good quality DC motor with a speed controller? I thought DC &y distinction _keeps_ the bulk of it's torque at low speeds, unlike a single phase AC motor.
I'm trying to find out what the benefit (over DC) a 3ph + VFD offers, but thus far I haven't gotten an answer. I'll repeat I'm not (at the moment) operating anything large. The largest lathe I have is a Prazi SD300, currently out of commission, but has it's own motor.

I agree with the VFD. I smoked the 1/2hp motor on my 9" model A a few years ago. Replaced it with a 1hp with a VFD from Automation direct that also converts from single to 3 phase. They also have them that will convert 110v single phase to 220v three phase. Prices start a little over $100 for the GS1. I have the GS2. You can wire your existing switches to it. I have it mounted on the wall next to the lathe for easy access.

Drives | AutomationDirect.com

Vince

OK, Ordered the motor off ebay. About to pull the trigger on the VFD from Wolf. A few questions.
I was looking at wiring up an Emergency stop button. There are 2 options for doing this. One cuts power to the VFD (and lathe), the other is using an Aux contact on the VFD. Cutting power to the VFD is easy, just use a contactor and have the E stop cut off the power to the coil.

The TECO VFD has a input that is programmable for an E stop so it uses the dynamic braking to slow the lathe. The only thing I can figure out, after reading the manual, is what the signal is. Is there a signal out on the VFD that can be used and run back to the input with the switch in series?

Also, do I need to buy the braking resistor?

Looks like the extension cable is $68. Talk about a Ripoff for a cable.

For wiring the drum switch as the fwd reverse switch for the VFD, am I going to need 3 or 4 wires plus a ground? I'm trying to figure out the wiring so I can order some of it now.

If I go with a contactor, there is no reason I can't mount it in the same panel as the VFD, correct?

Dunno how much the TECO's go for. The Hitachi's from Drives Wharehouse are very well priced. Your emergency stop should be able to get configured in the VFD with a logic level signal, and yes, there should be a line you can attach to a swtich to for this without adding any outside current. At least, that's how it works on my Hitachi. It has a number of inputs, you just program what you want them to do. They generally reccomend that you do not cut power to the VFD for emergency stop. You should not need a contactor.

Tojan, I looked at the spec's of the N3. It appears to be identical to the 7300CV perhaps an earlier model.I don't know why the cable is so expensive it was 29 dollars for mine at factorymation. All of your forward and reverse and estop functions will be fed from the drive,using the 24 volts from the drive if you decide to run external pushbuttons,however,with the ability of the control panel to be remoted why use extra push buttons and the associated wiring? Jim

It is my understanding that once you go below the actual speed of the 3 phase motor, you will loose hp/torque. So in theory, while a 3/4HP or even a 1HP motor will work, when you drop below the rpm of the motor, you will loose power. In order to compensate you will need to get a higher HP motor. I plan to use a 2HP on my 10L which is 1750 rpm. More ideal would be a 1-1/2 HP motor running at 1150 rpm. The math was shown to me on the yahoo mailing list.

An SB9 uses less power than a 10L, so it is possible that motor will be fine for you, just that it doesn't seem as though you are compensating for the rpm of the motor and/or how the HP is lost as you go slower.

As an example, if you run a 3/4HP motor down to 100 rpm or 50 rpm, it would have little if any power left.

With that said, the experts will most likely correct my skewed view if it is wrong.

Cheers,
Alan

Most VFDs are used in constant torque mode below the rated speed of the motor. This is because torque is related to the current squared on an induction motor, but the maximum current is defined by the wire size. So the VFD is configured to run at the rated current of the motor. This is normally approximated by having the voltage proportional to the frequency, but current VFDs are somewhat smarter than that.

End result is still that the motors tend to be constant torque below rated speed and constant power above it. Use an appropriately sized motor and VFD or a gearbox to expand the options.

VFD's vary speed by changing the frequency of the AC going to the motor. The motor will run at full speed @ 60 hz, lowering the frequency lowers the rotational speed (or 50 hz depending on country.) The VFD does not alter the volts of amps going to the motor. Therotically, within certain limitations, as long as the same amount of current is flowing through the motor it will produce the same torque. When you get down to the super low speeds, however, you will lose some torque, yes. This generally isn't an issue since the lathe has a back gear

unless I`m mistaken the vfd you linked is 3 ph input?? so you would still need a converter?

one of the Teco EV series 115V single ph input will work nicely with your new motor.

I had the Teco EV on my 9A with a Baldor 1 HP 1140rpm motor - it was a torque monster at low speed, I didn`t even need backgear.

edit- I looked at the link again -it`s single phase input.

Well I've gotten everything ordered. I'm out about $500. Got the 3/4hp Baldor motor(Ebay), the N3 230v 1ph 1hp VFD, a Nema box and mounting panel, the key pad extension cable, the braking resistor (all from Wolf), and an Allen Bradley E stop w/ enclosure and a AB key switch (Ebay).

I'm going to have to fabricate a bracket for holding the key pad and E stop box. Trying to decide if I should mount at the headstock end or tail stock. Sure wish I had a Welder right now. Might have to pay someone to make it.

Still need to get a stainless sheet metal top made for my bench. Right now everything is mounted on a double layer of 3/4 ply.


I'm really happy to hear about the good low speed performance with the VFD. One of the uses I'm planning for the lathe is Wet- SS Pin tumbling rifle brass in a drum I picked up off ebay a little while back. The drum is about 16" long, 7" OD. Has a 1/2" Stub out one end for clamping in a collet. It can't spin fast or the contents won't tumble. I was planning to use the back gear (still might). The VFD should make it easy to get the correct speed.

Hopefully I'll get it spinning for testing this weekend if the stuff comes in, or next weekend if it doesn't. Doesn't appear it should take to long to get it wired.