Preparing for possible shop move - no 3ph.. will need RPC for CNC Lathe

Im not in the thick of it yet... more just hoping and planning ahead (which is really against my nature )

Might be moving (home shop to BIG home shop)
Problem... I have a few 3ph machines...

Current setup:
Okuma LC10 CNC Lathe is at a friends shop who has 3ph 208v (manual says requires 60 amp breaker - has large DC spindle motor)
K&T 2H Universal 5hp 3ph is at my uncles shop with "B" phase as the local utility guys call it, which is supposedly just old style 3ph.
Wells Index 745 1hp 3ph that has a leeson VFD 2hp at my house running on single phase through the VFD.
Various other Single Phase machines and such...


Would end up moving it all (if all goes well) into a shop that has only Single Phase. So the generation of 3ph would become an issue.

So I have at hand a couple problems that I am in the midst of researching...

If we get this new place, funds will be tight which compounds the whole mess....

I dont know for sure how to figure out my requirements for total supply (and an added margin for expansion) primarily because of the Okuma. If I remember right, the DC motor is 13kW and I think max 180 or 200 volts DC plus the control. But I dont know what that would convert to in regards to idler motor size.

More info on the Okuma:
Okuma LC 10 with OSP3000 control
Has a transformer wired permanently to it, that can convert a range of 220 to 480 - and its output is supposed to be between 200 and 205 volts for the machine as per the Okuma Tech that helped me set stuff up. I am unsure which leg the control is on, but I would think I could figure that out with some hard core wire tracing. Manual calls for a 60amp breaker for the unit.


So now on to what Im trying to figure out...

Can the Okuma Control survive on RPC generated current?

Will that transformer help to stablize or condition the current from the RPC making it more likely be an okay setup? (Id assume good tuning on the RPC will be a must)

How much Idler HP would I need to feed the Okuma? (I seriously doubt I could ever come close to maxing out its draw... but Ive learned to never say never )

How much would one think would good as far as over estimation? At some point Id like to add a VMC - Robo-drill type machining center to the mix and if I did, the odds of both running at the same time is pretty high. But if the two CNCs were running odds are the manual machines would not be on at the same time.

Im sure there are a lot of things Ive failed to even think about... and am open to suggestions of other areas that need consideration as well as any input or advise on any and all that anyone is willing to share.

Thanks in advance....

Wade

60 amps into the Okuma means about 100 single-phase amps (actually 100 single-phase amps give you 57.74 three-phase amps), so just to run the Okuma you're talking about a very substantial RPC.

Let's say you needed 100 three-phase amps to run the Okuma and another machine, possibly the VMC. That's 173.2 single-phase amps.

So, unless you're planning on a 200 amp sub-panel for your shop, and most probably a 400 amp service panel for your residence, you're probably going to be stuck running a single large machine at a time.

Let's say your utility has no problem with 200 amps, but does with 300 or 400 amps. Let's also say that your residence is all-gas, so as to minimize as much as is possible the demand on your electric system. You then could apportion 40 amps to your residence and 160 amps to your shop, although those could be shared amps, and not a strict apportionment, and that 160 single-phase amps could be used to produce 92.37 three-phase amps, assuming perfect conversion, which isn't practically possible.

Now, you have some hope of powering your Okuma and one other large three-phase machine, but with what?

I would suggest a three part converter, incorporating a 5 HP first part, which would provide three-phase for your smallest three-phase machines, and starting power for larger converters, sized progressively larger. The smallest would start the next larger, and that would start the next larger (and largest, in this case), etcetera.

In its simplest implementation, you could manually control these converters using fusible safety switches. In its best implementation, you could automatically control these converters using interconnected magnetic motor starters.

You are quite correct about the Okuma. Being Japanese, it is a 200 volt machine. Import machines from Japan usually include a 208/240/380/415/480 to 200 transformer. This covers the three voltages usually found in North America: 208 Y, 240 ∆ and 480 Y or ∆, and the two voltages usually found in Europe: 380 Y and 415 Y (400 Y is also found in Europe).

Thanks Peter.

So what size of RPC idler (largest one as you would reference) would I be looking at to run the Okuma? And what would I need size wise to start it (as far as the secondary RPC - like the 5hp for example) And Im assuming that best to be completely setup to handle the entire draw the Okuma could create with the RPC than to go with taking readings on it as it runs now and working off of actual amp draw? I think in the book it says that 44amps is the "machines spec" and that they required a 60 amp breaker... so I wonder if 60 is overshoot of real need.

I would guess any VMC I ever could justify getting would be smaller in demand. (Im guessing 7-10 hp spindle at most?) So would it work to just run two instead of three and just plan that Id never run them at the same time and size the second for the requirements of the okuma?. I can operate with that, I was just thinking in terms of overall efficiency of production of having them both running and probably in reality, having them both running at the same time is not probably realistic due to the items I make and attention that they require during the process.

As far as power, IF we end up able to get the new place, the shop (actually both of them - but one is dirt floor) is already set up with its own 300 amp line and the house is independent and on its own "can" off the pole. (all I can say, is shy of 3ph power and its location for all but those that can survive in the middle of nowhere, this is a dream place) And the previous owner set things up right... but just couldnt afford getting the power company to string two more wires on 5 miles of poles to get 3ph to the location.

Would you happen to have links or suggestions on finding the wiring setup for something like you mentioned "automatically control these converters using interconnected magnetic motor starters". Something that you feel is well designed? Id much rather do it once right then have to do it again later to correct mistakes.

Ill be honest, Im very mechanically inclined, but when I get to AC current I start getting a little lost... so Ill have a steep learning curve to battle as I go along with this (hence starting researching early )


Thanks again for the insight.
Wade

300 amps should be enough ... more than enough.

That's almost 175 three-phase amps.

Single RPCs which can provide that level of power are known, but they are very expensive.

A better solution is a number of RPCs, each successive one being twice as large, or larger, than the preceding one, with the aggregate comprising your required maximum load.

Perhaps 5, 10, 20, 40 HP, or something like that.

A 5 HP RPC is easy to construct using off-the-shelf parts and a 5 HP three-phase motor.

If you can get good, used motors from a recycling center, so much the better.

No need to stick with 1725 rpm. A mixture of 1725 and 3450 rpm is fine. 1150 rpm, too. The RPCs will all exchange "synchronizing power" with each other, anyway, and will all remain in synchronism, one they have reached steady-state.

Once you know what the maximum load will be, and what your available idler motor capacities are, the design can be "fleshed out".

But, the basic starting point is the automatically starting 5 HP RPC, using a Steveco 90-66 potential relay.

So how do I figure out what I need motor size wise for the Okuma?

Thats one part that gets me... I have no idea what 44-60 amps would equate to in a 3ph motor HP...

Ill do some googling

"Thats one part that gets me... I have no idea what 44-60 amps would equate to in a 3ph motor HP..."

The quick answer is you sum-up the FLAs of all the idlers to get the composite three-phase amps.

The single-phase amps is then 1.732 times the FLA amps.

Is there a rough approximation of what the HP to FLA would be just for close guesstimate?

Like 5amp 3ph motor is 2/3hp or something?

I just trying to figure out what I might end up having in stuff to make it feasible... a case of.. if I spend 4k on idlers and parts and build it... I might start weighing that against a 3ph generator instead of RPC.


THanks again for taking the time!
Wade

"Is there a rough approximation of what the HP to FLA would be just for close guesstimate?"

The following is taken from the "review's copy" of the 2005 NEC, Table 430.250. The final printed copy is probably the same.

For 230 volts ...

5 HP ... 15.2 amps
7.5 HP ... 22 amps
10 HP ... 28 amps
15 HP ... 42 amps
20 HP ... 54 amps
25 HP ... 68 amps
30 HP ... 80 amps
40 HP ... 104 amps


So, for a 100 amp RPC (100 three-phase amps, that is), you could use ...

5 HP ... 15.2 amps
10 HP ... 28 amps
20 HP ... 54 amps

... for a total of 97.2 three-phase amps, and 168.36 single-phase amps.

As I initially described, the 5 HP RPC could be made self-starting, using a potential relay, and as soon as that RPC was placed on-line, you would have 15.2 three-phase amps for powering small machinery, or, you could use that RPC to start the 10 HP idler (which has no starting circuit), and that would give you 43.2 three-phase amps, or, you could additionally start the 20 HP idler (also no starting circuit) for additional capacity.

I think you can see that 5 HP alone, 5 + 10 HP, 5 + 20 HP and 5 + 10 + 20 HP are all possibilities.

Or, given the other data, above, you could configure a much larger RPC.

Ultimately, it all comes down to how many three-phase amps you need, and after that computation has been done, you then multiply by 1.732 to get the equivalent single-phase amps.

There are other issues, such as spinning the idlers at rated rpm before these are placed "across the line", in order to reduce the inrush current, etcetera.

But, the above numbers at least get you in the ball park as to steady state operating conditions.

Obviously, starting conditions are more extreme, but these conditions last only a few hundred milliseconds to a second, or so.

The table data is useful as it is average data. If you have actual nameplate data, then by all means substitute that actual data.

Try and find your local recycling center. These are often good places to find used motors at very low prices.

For an RPC, the shaft need not be perfect, as you can always cut off the external shaft(s), but the bearings must be good, and the rotor must run true. A motor with a damaged key slot is an ideal candidate for an RPC.

Fortunately, most modern motors use standardized ball bearings, and the bearing number(s) are stamped on the motor's nameplate, and their replacement is rather straightforward.

So Peter, If I have a 10hp RPC that can put out 28 amps, what does it take power wise just spinning, as if the RPC is running but the machine it's connected too isn't ?? Thanks, Mark

"So Peter, If I have a 10hp RPC that can put out 28 amps, what does it take power wise just spinning, as if the RPC is running but the machine it's connected too isn't ?"

RPC systems consume reactive power (also called imaginary power) when unloaded, and this reactive power consumption tends to go down as the RPC is loaded up, and real power is consumed by loads.

It is possible, even desirable, to add power factor correcting caps to improve the power factor.

Capacitors have a leading (+) power factor, whereas a motor has a lagging (-) power factor.

Adding just enough capacitance to correct the lagging power factor is usually done as the last step of RPC installation and tuning.

With a multiple idler installation, each idler would have its own power factor correction capacitor.

Okay, so considering my situation...
Im thinking that overall, my max need - at least starting out (can always add later right?) would be having 75-80 amps total... figuring the Okuma at 60 though I doubt it will ever use that much for the materials and parts I use it for - and the odd chance that I can run one of my manual mills at the same time - say the 5hp K&T.

Assuming I can find affordable motors... and the amount of power I think Id need... Would it be a better approach to go with a 10hp and a 20hp - making the 10hp a self start and using it to start up the 20 when using the Okuma - or is 10hp getting big enough that the self start part becomes overly expensive or problematic? And I should look to doing the 5 -10 - 20 route?

Im out in the middle of nowhere where recycling is not a common place... its even hard to recylce aluminum cans (have to drive 30 miles for a place to drop them off at) - so Ill have to do some digging for a place to chase down motors like that. I have a couple ideas of people to check with, but Im not over optimistic - unfortunately out here 3ph motors are more common - being used on spinklers, wells, gas wells, and so on...

Thanks again for all the information!
Wade