3phase servo retrofit

[whiteriver]

I have a 3 phase 5 axis robot and need to retofit it to single phase. Rotary phase converter not a option. Will use Mach3 to controll.
Current motors and drives are 3 phase.
Looking at going with Steppers and gecko 201's or Dc brushed servos with gecko 320 or 340 drives.
The two larges motors are Fanuc 5F see attached pic for spec. What would be a equivilant size in stepper or dc brushed servo?
I have read over 400 posts here about servos but still don't know how to get from what i got to what i need. Voltage oz/in watts amps. How does it all compare?

Donny

[Al_The_Man]

The motors shown are 6Nm which is equivalent to 850 oz-inch. 2000 rpm max
If you go with a brushed servo you could use the 6Nm figure but remember that AC servo's usually have less inertia so you might want to go to a bit larger if you want the same speed as previously, those robots can really move. Worse case senario is that you may have to drop the acceleration if undersized, there is the usual limitations with steppers once you get up to the high revs.
Al

[Al_The_Man]

By the way did you look into the actual power required?, as 27Kw seems heck of alot as the main load is the motors and they are not that big. It may be worth looking into what you actually need in the way of rotary converter if the robot takes 220 3ph.
As it would save alot of grief retrofitting and it seems you have a good system in place.
Al

[whiteriver]

I had figured out that 6nm =850 oz in. But how does that relate to the rest of the world. That 6nm is torque stall. Not what it produces on average i assume.
If i went with a 2600 oz/in stepper (already have) would that work? If i went with a dc brushed servo. How many volts how many amps? Lets say i look at surplus center or ebay what would i need to find that would be equal to or better?
As for the 27 kw rotary phase converter. Its what a company sized for my application. 480v 20amp 3phase input needed. I can change the input on the transformer to 220 or 240 3 phase. But then i would need bigger fuses going in right? At 240V 3 phase i would need 40amps right?? Which would mean i would need a 80 amp single phase breaker to run it. Still not to sure about 3phase.

Donny

[Al_The_Man]

Just step back and think about this for a moment, lets assume that the main load for the robot power is the motors. Fanuc motors are pretty efficient, so, if you are going to replace them with equal or greater torque assuming they are as efficient as the Fanuc motors, the required (supply) power is going to be the same or greater. Now do you plan on aiming for 40amp at 240 volts? In any event that is no where near 27Kw, so how did the company come up with that figure?
You have the machine, so look at the size (va) of the power required for each servo amp, fusing etc. And attempt to calculate the actual power required.
Agreed the fusing will be doubled for 230 and also you may have to increase wire size where necessary to the transformers, but this is minor compared to a retrofit. Likewise if you find that the power required is within reasonable limits, it is not hard to build your own rotary converter. (see one of my recent posts).
If the robot was working when you purchased it, I would be inclined to persue this route first.
Al

[petek]

You might also consider finding single phase drivers for your existing three phase motors. I just builtamachine using allen bradley drivers single phase supply for three phase output

[petek]

another option to look at would be to find drivers for single phase supply and three phase out. I just built a machine and used allen bradley amps/power supplies single phasein and three phase out.Then you could use your existing mtrs.I believe the ones I used were their ultra 3000's.

[whiteriver]

Ok It would be nice not to do a full retrofit.
There is a dual stacked servo amp with one breaker on it 250V 15A. I don't know if that is for both amps or just one. They are intergrated into one unit. IT controlls both big 5f servo motors.
The next servo amp is smaller and has 3 removalble fuses at 250V 5A
The last two servo amps are the same size and part number 3 fuses at 250V 3A.

Break down of input to transformer #1 of 3. 480Vac 3 phase Line in to knife switch. Switch to 3 20amp fuses. to contactor, branch goes to power input module and other branch goes to 5kva transformer 30amp fuses out. There are 2 other transformers down the line a 1.1kva f1 20amp f2 10amp and a 1kva f1 10amp. I'll attach a couple marked up pics on what i got. I don't have a manual. They want $150 for them and if i have to tear it all apart then the manuals won't do me any good. If i can get power to it then i will get the manuals in the future.


I guess the reason they say use such a big rotary phase convertor is to double it for stability. Like i said 3 phase is all new to me.

I have a 25hp 3 phase motor laying around i could make a rotary phase converter out of if i knew what i was doing. And if it was the right size.

Thanks again

Donny

[whiteriver]

another option to look at would be to find drivers for single phase supply and three phase out. I just built a machine and used allen bradley amps/power supplies single phasein and three phase out.Then you could use your existing mtrs.I believe the ones I used were their ultra 3000's.

If i had to go that way what did those cost you if you don't mind me asking?

Donny

[Al_The_Man]

Break down of input to transformer #1 of 3. 480Vac 3 phase Line in to knife switch.
Donny

Is transformer #1 supplying the panel externally, i.e. can it be eliminated if you take the supply directly in to the disconnect (knife switch)?
Al

[whiteriver]

If i am understanding your question. The answer is no.
The power come into the disconnect then to a set of fuse blocks and a contactor then down to transformer #1. Transformer #1 is designated as the servo transformer. Looks like it steps the volts to 250 for the amplifiers.

I did a little looking and found a site that says you divide the amperage required for your aplication by 2.8 to get hp sizing. If I have 20a fuses on my inputs before the disconect 480vac line then i would need 40a fuses to have a 240vac input line? Is that right?
If i divide 2.8x40amp I get 15hp. So at that I would need a 15hp converter. Am I understanding correct?
Below is the text from the site.
(Transformers and electric equipment (welders, lasers, EDM machines, CNC equipment, computers, plating rectifiers, power supplies, etc.) can operate on the Rotary Converter. Use the same formula as for resistive loads to determine the proper size converter to use.)
(Resistive loads must use the Rotary type converter, the Static type should never be used because it would be damaged. There are two methods to determine the HP of the converter to be used. One method is to take the amperage rating of the equipment and divide by 2.8 to find the equivalent HP. The other method is to take the KW rating and multiply times 1.34 or divide by .75 to find the equivalent HP of the equipment.)

Donny

[Al_The_Man]

I would expect a 15hp rotary converter to be sufficient for this type of application, also remember that 40amp on 240 is not going to be the normal current draw by any means. This is the amount of protection rated for the equipment it is feeding. Fusing is typically sized for around 1.5 times full load current. If the servo transformer feeds all of the servo's then this is going to be your largest load, the control system itself is going to be around 1kva.
Al