Emco120 CNC lathe and 15HP Rotary Phase Converter

[JRouche]

Ok...

I finally hooked up the 15hp RPC I bought from American rotary.

This was supposedly a balanced, CNC compatible converter. It was...

I needed it to be as balanced as possible due to the lathe. The lathe is an Emco 120 CNC lathe. It is reported to be finicky with the supply voltage and the balance between the three legs.

I had to drop another 220vac circuit from my 100amp sub panel. I ran electrical metal conduit (EMT) from the sub across my work bench, of about eight feet, to where I mounted the control box for the RPC. The control box is a nice Hoffman enclosure that is large enough inside to run number six stranded wire without getting too crowded.

I ran three number sixes, two hot, one common, EMT grounded all the way.

I ran metal flex conduit from the RPC control to the 15hp Baldor idler motor.

I got some nice rubber isolator feet with the idler. She sits directly on the concrete floor. I had to remove some wooden subfloor to get to the concrete but I didnt want to run it on the wood due to possible noise.

From the RPC control box I ran the power line (rubber, looks like 10/4) for the transformer. The transformer is a step-up, multi tap to provide 380vac from a variety of inputs. There are also two additional outputs for plus or minus 5% the 380vac. Really a nice transformer (somewhat).

After getting her all wired up I hit the on button for the RPC control. Whoohoo, she started, and no crazy sparks. Oh yeah, I dont know anything about electrical stuff so dont follow my lead

Next I threw the disconnect. Oh, forgot to talk about that one. IMO you have to have a mechanical disconnect for machinery. Whether it be a removable plug from a socket or a mechanical switch. So I have a nice Square D, three pole switch there.

Cool, still no sparks or magic smoke.

The RPC idler was running smooth. No noticeable overhead lighting dimming or unsteady starting. Seemingly the soft start of this "special" RPC motor from Baldor is in fact soft start with a reduced current draw during light off.

With the transformer lit off I wanted to take some voltage measurements before committing the CNC control.

Basically I'll call the original house lines T-1 and T-2 and the generated line T-3.

I measured, with the RPC on:
T-1 to T-2 at 239vac.
T-1 to T-3 at 246vac.
T-2 to T-3 at 248vac.

All a little bit high?

But...If I figure it correctly (if not I'm sure to be corrected, I hope) the balance between the legs is 3.8%. The way I figured it was taking the highest voltage and subtracting the lowest voltage to get nine volts. Then nine divided by the lowest voltage to come up with my percentage. Again, I dont know a damm thing about math either so dont follow my path.

So, if I am somewhat close with my percentages 3.8% (3.7 actually) balance is well within the 5% needed.

I continued to measure and T-1 to ground was 119.5vac, T-2 to ground was 119.5vac and the generated leg was 217vac to ground.

This was all pre-transformer..

Post transformer gave me:
T-1 to T-2 at 388vac.
T-1 to T-3 at 408vac.
T-2 to T-3 at 392vac.

Ooh, the transformer is not as balanced as I had hoped, I think. Still not outta spec for the lathe. Unless my math is bunk, again... With the math I see 5.1% balance which is still alright.

Measurements again to the transformer common (close to ground).
T-1 to com was 229vac
T-2 to com was 222vac
T-3 to com was 231vac

That is 4% balanced.

Dunno...I finally switched the lathe power switch on and she fired right up. No smoke..

Two concerns were the sensitivity of the machine to line voltage and the regenerative braking.

I chucked up a piece of steel, basically the largest the lathe could handle. I ran the spindle speed from dead stop to max speed (4000rpm) many times trying to notice any problems with drive voltages/currents and braking currents. Evidentally the caps in the RPC are large enough to sink the re-gen currents and the RPC is overall large enough to keep the legs balanced even through power spikes. No error codes.

Overall I am real happy with the converter. I purposely bought one way oversize specifically to overcome the problems I thought would become an issue with a smaller unit.

I have a balanced leg, 5hp (Fitch Williams) unit I built to run my Bridgeport mill. The legs are fine turned to run balanced throughout the load. I dont think it would have been enough for the lathe which IIRC, is only about 5.5kw.

I am glad it works and I would recommend the company. A little pricey but after you by the Baldor motor and electrics you my have a few bucks in it already..

So solly for the long winded post. I actually cut myself off from a few thoughts.

Thanks, JRouche...

[Dave1]

That's pretty good. I also have a Emco Compac 6P, basically the same as your 120 cept a little older. If you want to talk Emco, drop me a PM. I'm running mine of a 10 hp rotary converter. Occasionally I have problems with the spindle not starting but I might be able to increase the idle voltage on the control board to help it start.

Dave

[palikalsi]

JRouche and Dave,

I am trying to setup a similar setup for my Bridgeport CNC mill and have not been able to get a balanced output. I have 20 HP American Rotary Phase Converter and a Step Up converter to convert 230 3PH to 460 3PH. The final output from the transformer is

T1-T2 : 478
T1-T3 : 442
T2-T4 : 468

The values drop when I turn to machine by ~20 Volts. The machine fires up fine but then spindle motor overheats and sensors turn off the controller. I would like to know if you are using two lines from the main house panel and only T3 (phase produced by converter) to get 3 phases or using all 3 phases output from the converter. Right now I have the transformer wired to use all 3 phases from the converter.

Thanks,

Pali

[Dave1]

Pali,
I believe my setup uses the three phases from the converter. I'd have to open the cabinet to make sure, it's been about 5 yrs since it's been opened. The outfit I bought the converter from guaranteed the output to be balanced.

Dave

[Al_The_Man]

I think you will find they all pass the 240v 1ph right through, a rotary convertor does not produce 3 phases, just an artificial phase. Even the solid state Phase Perfect advertise theirs this way, as only producing an artificial phase.
http://www.phaseperfect.com/files/al...s%20manual.pdf
Al.

[Dave1]

My converter is this one, 10 hp.
http://www.superiorphase.com/
Mine is hooked up as in figure 1, like Al mentioned.
http://www.superiorphase.com/images/diagram230lg.jpg
I checked voltages, just for grins, and they were within 2 volts across all legs while the machine was idling. The Emco transformer on the other hand was not good. Well, not as good as I would like. It's suppose to be pulling the voltage up to 380 but it's anywhere from 389 to 405. It has taps for plus and minus 5 percent, I may give that a try sometime and see what I can get.

Dave

[JRouche]

Hey Dave, glad to see another user of the Emco, great!!!!

The taps on the transformer do allow for some pretty good adjustment. I forget what I have mine set at but could look if you want.

My numero uno question of the day (off topic I might add).... What are you using for tool holders in the turret? I am using 1/2 tool holders but some mickey mouse clamps to wedge the holder in the turret slot.

I was hoping to see what others are using or what Emco envisioned.

Thanks for your help, JRouche



Ohhh yeah, whatcha makin? Anything you wanna share pics of. Always curious what folks do with their machines. The Emco has such a smallish working envelope it limits some operations.

[Dave1]

Originally Posted by JRouche Hey Dave, glad to see another user of the Emco, great!!!! The taps on the transformer do allow for some pretty good adjustment. I forget what I have mine set at but could look if you want. My numero uno question of the day (off topic I might add).... What are you using for tool holders in the turret? I am using 1/2 tool holders but some mickey mouse clamps to wedge the holder in the turret slot. I was hoping to see what others are using or what Emco envisioned. Thanks for your help, JRouche Ohhh yeah, whatcha makin? Anything you wanna share pics of. Always curious what folks do with their machines. The Emco has such a smallish working envelope it limits some operations.

For the clamps I used a piece of 5/16 ths key stock and drilled an tapped 2 10/32 holes for machine bolts to use them as a wedge (sort of) to hold 1/2 tool holders. Most of the tool holders are Tool Flow (they are nice) some are modified to get the 1/2 in. hight I needed. The clamp is what I believe Emco used if I remember correctly. The machine was purchased new in 1985 by the company I used to work for. It had been crashed so much it finally stopped working. They told me if I wanted it to make it disappear so I did Further inspection showed the ball return in the Z axis to be shot, screw was good though. Being the cheap skate I am I machined new returns out of 12L17 to replace the Bakelite ones Emco used (poor design) and it worked out very well. I did have to get some new balls as some were missing. I also ended up replacing the spindle phase angle control board and Z axis driver board. 5 grand to do that (YIKES) but it has been running great and very accurate (can hold .0001 on a good day, it hard to do because the offset can only change by .0002 minimum) It's also a 6P (pneumatic) so I can open and close the chuck by M25 and M26 so I can use a bar puller. I can pull up to 12 inches of 1/2 stock. I modified the draw bar by drilling it out.

Dave

[JRouche]

Thanks Dave. I guess my tapped, little pieces of metal are about right then.

What are those buttons?

Mine is a manual, no pneumatic chuck. I would eventually like to adapt a 5c chuck to the nose. Future project. JRouche

Oh, to keep this on topic, the RPC is still workin great

[Dave1]

Originally Posted by JRouche Thanks Dave. I guess my tapped, little pieces of metal are about right then. What are those buttons? Mine is a manual, no pneumatic chuck. I would eventually like to adapt a 5c chuck to the nose. Future project. JRouche Oh, to keep this on topic, the RPC is still workin great

Those are knobs for a charging handle on a FN-FAL.
I adapted a manual chuck also for the bigger stuff (if you call 2.5 inches big)
My 10 hp RPC is about maxed out on the new (to me) Takisawa lathe though, it really groans when the spindle is stopping but it's holding it's own. Sweet.

Dave