[mrmachinst]

I built a 20hp rotary phase converter and have been running this lightly used machine for a few weeks now. Robert E. Morris rebuilt the spindle motor prior to my buying it from a dealer. Fired it up after running it last night and it blew the F7 fuse (Alarm 3 on top board). Maintenance Manual says to check the Transistor units buy measuring the resistance between base & collector/emitter but I seem to be getting good on the first half and bad on the second half of each one. Do I have to remove any terminal wiring before checking this?

As a side note, the line running down to my barn is pretty long and I believe there is a small voltage drop on surge ( lights flicker/dim ). I can't comfortably get it over about 2200 RPM before the spindle drive starts to 'cog'. Will only rev up to 1100 RPM from stop so I start at 6" diameter G96 and feed it down to the work with a G50S2200. Seems to have been working OK till now!

Any insight into this repair will be greatly appreciated!!

[underthetire]

88 is probably a fanuc spindle drive in that one. Post the drive type, there were several ones. And what size wire are you running to the machine. Voltage drop enough to dim lights = bad.

[mrmachinst]

Thanks very much,

Running 6/4 all the way but a portion is Al. and it's quit a run from the fuse box in the house to the barn. Probably 200' total. I wasn't sure where to look to definitively find the SDU type. I wasn't to impressed with the performance of the 20hp phase converter. I'm considering stepping up to 480V and back down for the run out to the barn with a pair of 15kva transformers. Any thoughts?

The paperwork stored in the control says
FANUC DIGITAL SPINDLE SERVO DATA SHEET
MODEL NO. A06B-6055-H208
P.C.B. A208-1001-0120
SPINDLE POSITIONING CKT A06B-6044-J701 ( don't know what this is ) Alarms out when I try spindle orientation.

Thanks again!!

[underthetire]

So you have 480 available? Thats the way to go, get rid of the phase converter. You should be running CU wire all the way, and I think #6 is too small for that length of run, especially alum. wire. If you starve the drive ( and the part # you gave is the Fanuc spindle drive) of available current, it will keep blowing transistors. No spindle orient on LB15's, thats why it alarms.

[mrmachinst]

Thanks again,
No, I was thinking of stepping up to 480 and back down to 220 in the barn with a pair of transformers but after thinking more about it, doubling up the line and ditching the aluminum portion is what I'm going to have to do.

I have the manuals which point to the transistor modules. Do I have to disconnect all the wires from the top of them before I can check the resistance?
Thanks for the help.

[underthetire]

I believe you do need to isolate them to check, been a long time. Being a Fanuc drive you have a lot of options for parts, just don't go through Okuma for them. Fanuc has the transistors in stock, and i'm sure you can get them from T.E.S. as well. If you fix your wiring, and keep blowing them, it's probably a bad top board on the drive. Fanuc can come right to you with all the parts in hand and repair on site if your in a hurry. Post a how to on the fanuc board here, I used to have a full check sheet on those, but who knows what I did with it.

[nlh]

We use a phase converter to run our CNC equipment. It's capable of starting 20hp from a cold stop and running an accumulation of 80hp. We run #2 copper wire to all our "larger" equipment, including the LB-15, #4 to our smaller machines. This runs 2 mills, and 2 lathes (soon to be 3), but never all at once. Usually 2 at time, but have run 3 machines in total at the samte time. We will be looking for a larger one in the very near future. The LB-15 will still dim the lights slightly upon spindle decel, but this is the only time. I would suggest you run copper wire and/or get larger phase converter (if you absolutely have to run one). The one we have came from a radio station and was told by the OEM that is has a lot of "filtration" built in for smooth power output.

Keep in mind, with a converter you will have 1 leg of the 3 phase power that outputs higher than the rest. I don't know if it matters on the Okuma, but on my Mori lathe that leg HAS to be on the right side (R,S, or T) or it will blow fuses. Same for one of our mills. It would be worth looking into on the Okuma as well.

Hope this helps.

[Algirdas]

We use a phase converter to run our CNC equipment. It's capable of starting 20hp
is there some particular reason to use one?

[nlh]

I live in a rural area and commercial 3 phase isn't available at reasonable rates. Thus a phase converter will take the incoming single phase 220v, and convert it to 3 phase 220v.

That's the reason.

[mrmachinst]

All very interesting guys, and encouraging. I suspected that the line was too small for what I'm doing. NLH, "that leg HAS to be on the right side (R,S, or T) or it will blow fuses" I'm not sure what you mean here. Could you go into some more detail? The hook up inside the machine is L1, L2 & L3. Is the heavy delivery wire your talking about running to the machine from the converter or from the power source TO the phase converter. What kind of distance are you going? My home built phase converter is from a kit and has run capacitors and my voltages are 240, 230 & 220 at the 3phase output. Okuma manuals state the machine need 'aproximately' 200 volts. The idler motor is a 20hp. The Lb-15 is 10/15hp but has a stated demand of 21KVA max. Braking is regenerative but does this actually use power? Seems like acceleration is harder on my power source.

And what's the action of all the 220V/200V coil tap switches on the power supplies inside the control of this machine? Can switching these help in a low voltage situation?

My plan at this point is to run a separate 150' 60amp 4/4 gauge line to my phase converter and park the phase converter right next to the machine.
Thanks again,

[nlh]

mrmachinst,

From the phase converter you'll have 3 legs, usually labeled R, S, & T. L1, L2, L3 are just another way to designate this. One of these legs will put out more power than the other 2. This is the generated leg.

On some machines (but not all), this "wild" leg needs to go to the right spot in the machine or fuses can blow, other funny things happen. On my Mazak it does not matter becuase it goes thru a transformer that allows you to step or up down to match your incoming voltage. It also helps to isolate any power fluctuations.

Now I'm not sure how the Okuma is set up. It's been awhile since it was hooked up. Just something you may want to look at. I am no electrical or electronics expert, just have enough experience to keep myself (and some others) going.

Make sure your taps are set so that the voltage output to the drives, power supply, etc is as close to 200V as possible.

Good luck

[underthetire]

Commonly refered to as the stinger leg. I'm a little concerned about the difference in the other two legs, they should be within a few volts of each other. Call REM and ask what terminal the stinger leg goes on, I thought it was the center one on an Okuma, but i'm not positive. The spindle drive should have a toggle switch on it for 200/220 volts.

[mrmachinst]

I've been able to purchase the replacement Transistor Modules for this unit but when replacing them, one of the two components strapping the 1st and 2nd halves of TM-4 in the control broke. It's the only Module that has these two components attached and I don't know what they are. Their axial components that are shaped like little white spheres where the 'functional' part of the component is. White in color with some small green dots around the perimeter and a stripe. Does anyone know what these are and what value/wattage ?

Are these varistors?

Thanks,
Will

[mrmachinst]

Ok guys, I've fixed my machine!! I felt that an explanation of what I did could help people in the future.

I called Fanuc and explained that I was doing a repair to a drive and needed the part number for a part located between C1 and C2 of TM4 and E1 and E2 of TM4. The fellow on the phone didn't use the actual letters on the modules like I did which are written on the units themselves ( 'C' for collector, 'E' for emitter ). He called them simply terminals 1&4 and 3&6 and stated that this was the 'regen circuit'. I'm thinking the spindle regenerative braking which shorts one or more of the spindle motor windings across a large resistor to brake the spindle. He was nice enough to give me the part number for these components but told me what they were, 9amp 600volt diodes. I got some on Ebay and installed them along with TM1 and TM4 which were bad. These can be checked in the machine with with the wires still connected. Basically, nothing should be shorted. If anything is reading less than 'hundreds of ohms' the module should be pulled and replaced if it in fact checks bad out of the machine. Put more white heat-sink compound on the back when replacing them. A little of this stuff goes a long way so just use a very light film of the stuff. After I did this along with replacing the F7 fuse and installing a 4/4awg service line on it's own 60amp breaker to the phase converter, when I tried to start the spindle I was getting a alarm#12 on the drive which is 'over-current' in DC link. A used a 'megometer' to verify that the spindle motor windings weren't even marginally shorted anywhere. This is a device like an ohm-meter but is very sensitive up to 100+ megohms and sends a high voltage through the windings to make these readings. Every thing checked out OK. I then took a look at where the two bundles of cables go to the top board through two connectors. Right next to these connectors are a bunch of transistors about the size of a stamp and have metal heatsinks attached to them. I check for shorts anywhere and none were shorted. Next to these transistors are 6 or so small push in PC board mounted fuses that have no indication of whether their blown or not. Their clear plastic with the ratings printed on the top. These fuses are about 1/8" X 1/4" and are easily overlooked. I pulled each one of these and checked them. One of these tiny little fuses was blown and I replaced it from the spare parts bag in the control cabinet.

Bingo! All fixed. Thanks for everyone's input on this.