Powering up lathe: Denied. It's always something. Ideas?

pontiac428

pontiac428

John Newman
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Apr 23, 2018
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This is for my Nardini 1760. I saw it run under power before buying, so start there. I wired up my RPC, tied it to the power panel on the lathe, and... nothing. RPC is putting out 230v on all legs, 3-ph output breaker is set, master power is through to the lathe panel.

Circuit breakers are set and the contactors pass the PTT test.

Interlocks. This is what I think is going on. There is a head gear cabinet with a plunger switch, and an operator's e-stop. Both of these interlocks work, I can hear the mag switch cycling when I move them. There is a lock out/tag out disconnect in the panel, it's a rotary switch that works, but it may also be a plunger switch to interlock the electrical panel door also- I'll check when I get home. Then there's the panel indicator lamp that lights when power is ready. It's a Sylvania 27v bayonet bulb with two filaments but only one contact on the bottom, which is weird. It's also burnt out. So I am hoping the BULB is not part of the interlock like a damn charging circuit. I'm really not sure.

Then there is the neutral/brake switch, which checks out visually and mechanically.

There is also the possibility of oil pressure switches as an interlock. No clue if pressure sensors even exist, and I think the 3 oil pumps are mechanical anyway.

I do have schematics, which is how I plan to spend my evening. The schematics are the key to the whole thing obviously, but if anyone has some simple ideas to try...

I also plan to swap two legs on the 3-phase just to be sure.

Any thoughts? I was pretty sure I'd be up and running last night.
 
One of the first things to check is that you are not using the generated leg to power your controls. If that is the case just switch to one of the other power legs. That may not be your problem, but it is quick and easy to check.

Ted
 
I had a similar problem with my 3 phase Clausing Lathe. I saw it run just minutes before loading it on my trailer. 2 years and 2 monies wasted on 2 VFD's I spent $100 on a Megger. Motor megged out borderline. I had it rewound. Now it runs like brand new and meggs out above 1,000 megaohms. I would start at the obvious places first and verify there is 3 phases getting to the motor leads, if by chance you are getting all 3 phases megger the motor. If the motor is good and you have no voltage getting to it, I would take one bite at a time. Seems simple but if it ran before you loaded it must be an open contact in between.
 
I went did what I chided a user for just the other day. I was out of the shop and sat thinking about shop problems (that's a twist for you), and without the work in front of me, started a thread without all my info. Sorry for that!

I finally got to study the schematics last night. It was way past my bedtime. I traced everything out and it all makes perfect sense, there are no hidden interlocks. Everything checked out, and I was about to give up and go to bed when I realized I better check where the control transformer gets its power from. In the case of the Nardini, it's L1 and L3! I was expecting L1 and L2, which are the natural legs of the RPC as I wired it. So I am feeding the wild leg to the control transformer, and the wild leg has a good bit of voltage float until a load pulls the voltage into balance. I was using the same scheme I used for my mill, which used L1 and L2 for the controls, but there is no chirality convention in 3-phase for which is which. That is simply a nuance of the system.

I hope I can get in there and swap those wires before the weekend. I'll keep this thread going until I'm operational. I'm really lucky that unintentionally laying the lathe on its back did not damage anything inside the rear electrical panel. There was less than 1/4" of misalignment from the panel box getting tweaked during my lathe's repose on the concrete, but five minutes with a bottle jack and I got the box straight. Everything is well protected on DIN rails, and the box is ample sized, so I dodged a bullet there.

I did order the oddball T2.5 panel lamps. Goofy things. I didn't want to try LEDs because I still hadn't verified whether the lamp was an interlock (hey, it's a thing in some sectors). And the LOTO power switch has no plunger door safety, just a plain rotary switch, so that's good.

It's been almost 6 months since the lathe arrived. Just a little more cleaning and painting, then I can put it back together and begin the tests! I feel like I've been restoring a car in terms of time/cost/detail. The lathe is in great shape, it was just really dirty- and topheavy.
 
talvare said:
One of the first things to check is that you are not using the generated leg to power your controls. If that is the case just switch to one of the other power legs. That may not be your problem, but it is quick and easy to check.

Ted
Click to expand...


pontiac428 said:
I realized I better check where the control transformer gets its power from. In the case of the Nardini, it's L1 and L3! I was expecting L1 and L2, which are the natural legs of the RPC as I wired it. So I am feeding the wild leg to the control transformer, and the wild leg has a good bit of voltage float until a load pulls the voltage into balance.
Click to expand...


@talvare for the win!

:clapping:

Brian
 
Yep. It's all I can do to take the rest of the day off, go home at noon, and... but, no, I've got meetings.

I'll just put this here for my future reference, since it's convenient.
 

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