Would this Baldor 10 h.p. 3 ph. make a good 6 h.p. output RPC?

[Danl]

Thanks, guys, for all your insight. I need to do a little more homework, maybe find out where others have sized RPCs to these 6 h.p. lathes and make sure that I've got all my ducks in a row before laying out $$$ in making this all work. I believe the consensus of the above comments is that this motor will work.

Dan

[lakeside53]

Sure that motor (like almost any 3 phase motor) will work as an RPC. But... as you will keep hearing, if you have two speed motor on a Nardini (any many other 2 speed motors on similar lathes), it may not. The specific Nardini I have first hand experience with is a 1440E and is 6.8hp (in high speed)

[wierdscience]

In that case,maybe stuff the Baldor in the lathe and buy a VFD instead?

[JRouche]

In that case,maybe stuff the Baldor in the lathe and buy a VFD instead?

Thats the ticket!! JR

[J Tiers]

That motor is a bit of a pig also, as it is rated at 6-7 kVA/HP locked rotor current. Typically, a code "H" would be up to 5 HP, and a 10 HP would be the next lower code, meaning less start current. So it would be normal to start that motor with some form of reduced voltage starter.

But there are MUCH worse motors than that. As a code "H" motor, it is on the high side of mid-range. The scale goes up much higher, to a code"V", which has more than 3x the kVA/HP of that one. And the code letters are not LIMITED to 5 HP with "H", it's just more typical of ones meant to start "across-the-line".

As for the Nardini motor, it would not be such an issue if it were not a 2 speed, and if it ran continuously, with a clutch setup. As 2 speed, it will be started more often, since it is stopped to switch speeds. And in that machine, it is started and stopped with each cut, no clutch involved.

Add to that it being a high start current motor, and there is a real issue. The Nardini seems to be the worst of all choices as far as it's motor setup.

I'd like to know the code letter on the Nardini motor, if it has the US information on it.

Maybe it could be set up with a reduced voltage/reduced current start system. That might allow it to start with some reasonable RPC.

Or maybe just give up and drive it with a VFD, where you could possibly even set it up in low speed, and just overspeed it for the other. Even if that is not wanted, it would give a soft start and should be able to start either speed range. Naturally, you would again only switch ranges when power (VFD output) is "off".

[polaraligned]

I believe the consensus of the above comments is that this motor will work.

Dan

I must have missed that consensus. I would listen to Lakeside53's advise, he has experience powering these 2 speed lathe's.

[J Tiers]

I must have missed that consensus. I would listen to Lakeside53's advise, he has experience powering these 2 speed lathe's.

Agree.

The motor will make a fine RPC.

Even so, it might not start that Nardini with the original Brazilian WEG motor, unless some form of reduced voltage/current starter is used.

[Danl]

Lakeside53 posted his last just after I posted that bit about consensus. I do not even have the lathe in my shop yet, but Lakeside53 obviously has experience with the exact model I'm buying, so I will definitely defer to his insight and not go with that Baldor. It is on CL in Portland for $324, but I will not buy it.

Lakeside53, would a 15 h.p. RPC work? Or perhaps ditch the existing WEG motor and go to different 2 speed 6 h.p. motor?

Thanks,

Dan

[Rich Carlstedt]

Dan
I thought you owned that motor.
If you have a chance, go buy an old motor. A big old motor.
usually they are open framed and have lots of Iron and Copper.
The heavier the motor, the better.
The newer motors are "high efficiency motors" or "VFD rated " and do not make as good a RPC as the old motors do, because they do not have the needed saturation.
Hey, they may not look nice, but the chance of them working well is much higher

Rich

[Danl]

Rich, do you think this one might be ok? It is here on CL also, 15 h.p.


This is an RPC someone is upgrading from in his shop, obviously not a capacitor start. $500.

[lakeside53]

Metalmagpie has a 15hp rpc I designed powering a Nardini 1440. The only way to reliably start it in high speed and highest gear is for him to start his iron worker first. This is pretty good indication that the 15hp is not sufficient. Also... it had a habit of blowing the 30 amp output fuses - another good indicator it was slow to spool up due to generated leg sag. That was "overcome" by putting is a D curve 40 amp output breaker in the place of the fuses. Excessive, not "code", but... Also, he can make it start by switching from low to high speed on the fly. I don't know if that is valid or not on the Nardini - My 7.5hp Howa specifically says not to and if it do there good fireworks from the contactors if I do.

I wouldn't go less than a 20hp RPC motor but that comes with it's own issues of higher single phase input current and larger wiring sizes.

Other 2 speed motor? My experience is they are all pigs, hard to find and often expensive.

The pic above looks like a kitset. I see no balance caps - just a motor, pony, loose breaker and disconnect. You will need to manually engage and disengage the pony.

VFD : If you use a vfd and a single speed motor, you loose nothing. At 1/2 speed (30hz) you will have 1/2 of 60hz power, just like the original two speed motor. To correctly implement a vfd you will need to remove/bypass a great deal of the existing control system. Single phase input 7.5hp vfd are not inexpensive. You can power a surplus 3 phase vfd from an rpc. If so, you will not need to dramatically oversize the rpc. You could also power the existing motor from a vfd ignoring the two speed switching and connect only in high speed mode.

[smithdoor]

I had a shop made rotor phase converter. Work for over 25 years till I sold shop.
I can think of any electronics that work for more the 7 years may be cock???
See drawing below for a low cost one

Dave

Dan
I thought you owned that motor.
If you have a chance, go buy an old motor. A big old motor.
usually they are open framed and have lots of Iron and Copper.
The heavier the motor, the better.
The newer motors are "high efficiency motors" or "VFD rated " and do not make as good a RPC as the old motors do, because they do not have the needed saturation.
Hey, they may not look nice, but the chance of them working well is much higher

Rich

[flylo]

25 HP Phase-O-Matic which is a great brand $1200 OBO Bay item number:142183752285 Might get it for $7-800, never know. I bought the exact same one for $250 when the gent was finally able to put in power company3 phase. Never used it, never need over a 10 HP.

[lakeside53]

On the above, check that it it has a 25 hp motor, or whether is simply "rated" to start 25hp of several motors. And.. What is the largest hard-staritng motor that can be applied? Things are getting better now but in the past there have been some wild claims that mislead.

[metalmagpie]

I have a Nardini 1440E Mascote. I built a 10hp RPC using a massive Toshiba motor. Didn't touch the Nardini in high speeds. I swapped in a 15hp idler and now it works except for the very highest speeds. To use those I start on low speed and after the lathe has spun up I toggle the motor switch to high speed. I use 40 amp slow blow output fuses on the RPC because the 30 amp ones I started with kept blowing.

metalmagpie