Nardini 1440e 440v to 220v conversion

So, hi

I'm finally setting up my home shop with a mill and lathe, both of which are/were wired for 440v service. To bring you up to speed, I installed a 100amp subpanel in my garage and have already wired the building, and ran an outlet to my Kay RPC (pictured). The nameplate rating might look underpowered, but according to Kay, this RPC will run and start a 1.5 to 7.5hp motor. Built this little cart to get it low enough to roll under my lathe. RPC runs great, and I wired my Bridgeport to 220v no problem as the diagram is right on the motor. Runs awesome.


So onto the lathe. The motor is complex (to me). It's a two speed motor, which also runs forward and reverse. I've attached a picture of the tag on the electrical cabinet which shows that it's designed to run on 220v. Also attached in this post are the two wiring diagrams from the owners manual.

So inside the cabinet is a Waltec transformer for the control voltage (attached photo). Looks like I just have to change the leads on the right side according to the diagram.


Now it get's interesting. The motor is an Eberle, and the nameplate rating has been re-stamped to 440v. Not sure if it was just rewired, or rewound to achieve this.


I took the cover off the box on the motor which has a little diagram showing the high/low speed wiring circuit (silver sticker).

On the junction block inside the motor box there are 6 studs, 2 wires per stud (12 total wires). 6 wires come from the cabinet, and 6 come from the motor. I made a diagram of the labels. All of the "1T*" in my diagram are from the control, which are marked with yellow clip tags found throughout the control cabinet. The motor wires are the number/letter combinations, which have both a metal tag and a sticker.


I've been studying the connection diagrams on this website, but not having much luck figuring out exactly which arrangement I have. The delta/WYE vs high/low stuff is confusing on a two speed motor. I don't know if the high/low is referring to the voltage or the speed: Motor Connection Diagrams

Your motor has been rewound for 460 volts only.

The YY connection is for the high speed and the delta connection for the low speed.

If it was a dual voltage motor, there would be 18 leads coming from the motor. 6 to the terminal block and a bunch of splices.

A good motor shop may be able to reconnect the windings for the lower voltage, but normally it will be a rewind.

Bill

Thanks Bill.

Cascade Electric is right near my workplace, and I have a good relationship with them so I'll contact them on Monday.

I was reading that the Kay converters can be configured to run 460v, but I don't know anything about step up transformers and such.

I also have a spare 5hp 230v 3ph 1725rpm motor, but it doesn't have the electric brake built in like the Eberle does. I can see that getting old real quick, plus I wouldn't have my low range gears.

Another option would be to sell the damn lathe and get something else!

The motor in your lathe uses whats known as a Dahlander winding. All 6 of those leads on the motor go to the hi/lo switch on the front of the lathe. The wiring diagram shows how it switches them around. Bill is correct that the motor is 460V only. Not to bust your bubble, but your RPC is most likely way too small to start the lathe, regardless of what the manufacturer told you. I have the same lathe and my 15HP RPC will only reliably start the lathe in low speed. There are several discussions on this site about Nardini's and RPC's.

The Nardini I got running for a customer, we just put an 1140 RPM motor in it so it was half way between high and low. If he ever needs faster spindle speeds, the VFD route will take care of that.

Those motors take a big RPC to start them in high speed.

Bill

The more I think about it, the idea of ditching this two speed motor sounds better and better. I really hate lathes that don't have a manual clutch and brake. It was the only reason I hesitated to buy the Nardini. If I was only turning rifle barrels it wouldn't be too bad. But it's nice to have a clutch for many situations such as turning large parts, jogging things around so you can inspect threads, and just not having to find neutral and move parts by hand all the time. The high amp spike required to get the entire gear train moving in high range is just another nail in the coffin for this thing, so I don't think it's worth getting the entire motor rewound.

I've got a spare 5hp 230v 1750rpm motor that could be adapted (The original motor runs 1760 in high range, and 800 in low range).


If I pick up a $400 vfd, I can soft start the motor which shouldn't piss off the rpc as much. And the vfd will serve as a brake. I should probably go with a 10hp model, but I think this 7.5hp unit should work fine for most work. I can always gear down if I need more torque: GS2-27P5

The only negative to me would be running the lathe off that little touchpad. Being a conventional guy, I prefer to control the chuck with a handle on the apron. It looks like this vfd has remote inputs, so I could potentially wire the factory spindle fwd/off/rev handle on the apron as a controller. Any thoughts on this proposition?

Well, I contacted the folks at automation direct today. They said with a 3ph 230v input to 3ph 230v output vfd, you do not upsize. So their 5hp unit would be the one to choose. However, because the Kay rpc does not produced balanced output voltages it will not work for me anyways. They said a vfd can be sensitive to input voltage resulting in "issues" which they did not elaborate on. I took a look at the test sheet that came with my rpc and sure enough, the legs are all different:

Input voltage: 244
Output V L1: 268
Output V L2: 282

Then I did some research on the Kay industries website, and they clearly state that it IS possible to run a vfd after their converters: Phase Converter Frequently Asked Questions

So, I'll have to get a hold of them tomorrow and see what type of vfd is recommended which could handle the imbalance.

Or I could try to find an appropriate 460v step up transformer and run the lathe as it is. I see a few used ones on ebay in the $400 range with enough kva to run the motor. Not sure how well a transformer would hold up to the starting surges from the lathe though. And it would be yet another big ass piece of equipment I have to find a spot for in my one car garage workshop.

I ended up yarding out the Eberle motor and making a mount for the 5hp US Motor I had sitting around. I machined a sleeve and step key to fit the original 1.5" bore sheave on the 1.125" shaft because I couldn't find a new replacement with the same dimensions.



So nice to finally have this thing up against the wall where it belongs. The motor doesn't have the balls to start the spindle in the highest range (2000rpm), but other than that it works well. The smaller motor starts the spindle gently, and not having a brake is actually perfect. I run an American Pacemaker at work, and it spins so smooth it feels like it will coast forever if you don't manually apply the brake. The setup on this lathe is just about perfect. You can see the RPC sitting under the chip pan.



I'll revisit the vfd later on when I get annoyed by not having enough speed range choices. The people at Kay have been very knowledgeable about the subject.