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I am completely clueless when it comes to electricity and hoping you all could advice me.
I am considering buying an 8hp Fadal CNC Milling machine, salesman tells me mfg can build with single phase motors so that i can run this machine from my home.
What, if any, drawbacks of running CNC in single phase? Do i lose horsepower?
How can i determine if my home has sufficient juice to operate this machine?
Any advice you can provide would be very helpfull and appreciated.
The main thing to convert to single phase is the spindle motor (8hp?), That is quite a large motor for 1 ph, single phase motors are not as efficient as a 3 ph equivalent and will take in excess of 30 amps, but this can be provided by a 240v 1 ph supply.
You should provide a suitably large conductors to avoid voltage drop on spindle start.
That is a large machine for home use, if you have the work to support it, I would look for an industrial unit that can supply the 3 ph.
Al.
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
8hp roughly speaking equates to 8kilowatt. Allowing for starting surge when the motors are turned on the supply should be able to handle maybe 12kilowatt; on 240volts single phase this is 50amps. More or less the same as running your clothes dryer, oven and a full house air conditioner all at the same time.
The machine will never use even the 8kilowatt, let alone the 12 all the time but your wiring to the machine needs to be able to handle the brief use. The electrical servcie to your house is likely somewhere between 100amps and 200amps and you should be able to get some idea which it is from the main incoming breaker on your distribution panel.
With a 100amp supply maybe your clothes are not going to get dried and you might have to eat a very rare roast if you insist on using the machine all day. On 200amps you should be able to dress dry and well fed.
Also horsepower are horsepower no matter whether the supply is single or three phase; the only difference is the amount of amps used. 12kilowatt on three phase 240volts is just under 30amps.
070331-1910 EST USA
MrMagooo:
What kind of spindle drive motor is on the machine. I suspect it is DC brush type (unlikely), or a three phase induction motor driven from a vector drive or variable frequency control. In all three of these cases there will be a rectifier feeding filter capacitors to generate the DC required by any of these three drive types.
Hopefully a machine designed for single phase will have more capacitance than the three phase unit to keep the ripple level the same on the single phase unit compared to the 3 phase unit. This bank of capacitors or a similar bank will supply the servo drives. In addition to the spindle motor and servos there may be other motors that are normally 3 phase induction motors that need to be single phase, such as the coolant pump.
If you do not do heavy hogging you may never go over 50% load on the motor other than during spindle start or changing to higher speeds. In any event if you had a load current problem you could just take lighter cuts. Short time peak power to accelerate the spindle should not be a problem. The capacitor supplies much of the peak energy for acceleration.
On one of our HAAS VF3's the load current to one of the 240 V three phase lines is around 1 to several Amperes with the spindle off. I can not check it now.
There will be a low level of residual power consumed when the spinlde is off. This will increase as the spindle load increases.
Take a clamp-on ammeter to your Fadar dealer and check the load current on a single phase machine like you want to buy and check the current under different load conditions. Ideally you want to use an RMS reading meter, however, most meters are average reading calibrated for RMS on a sine wave. The input to a capacitor input filter is not a sine wave.
If the dealer does not have a machine for you to test, then at 240 V ask for load current values at spindle off, and several load levels up to and at 100%, and at 150%. All at maximum RPM. Get the values in writing and guaranteed.
.
MrMagooo,
Will this be a new machine purchase or a used one? I've never heard of an 8HP Fadal - Be carefull ? Fadal Machines can all be wired up single phase, although I am not sure about the new FX series or the Fanuc machines. Keep in mind however you will loose 25 - 30 % of the torque / HP. You might consider a rotary phase converter instead.
IF this Machine is being purchased from the Manufacturer. I will be wired for single phase if requested. The only 3 phase motor on a Fadal with out spindle thru coolant is the spindle motor. How ever it is powered by an Inverter which when wired correctly (done at factory if purchased that way) can run a three phase motor from a single phase sorce. It will also have a single phase transformer with it to step down your line voltage to the 110vac to run the solenoids and relays as well as 5vdc powersupply for the control. As for power a 65 amp circuit running off your 240volt 200 amp box should be adequate expensive but adequate. As some else mentioned Horse Power is Horse Power so once at speed there will be no noticable difference what you will see is in rush problems. When you turn on the spindle, and rapid two or three axis simultainiously. And the load on your line at your main panel is up there (your doing laundry and using an eletric dry, water heater, have all the televisions in the house on and someone is blow drying their hair, you'll see a dip in voltage or a brown out occurance. IF this is a normal 200 amp main, you shouldn't see any of this if your miserly in the use of other electricals around the home.
Hello,
I have a similar setup that I run from 240V single phase. I'm running a 15HP rotary phase converter at 1200RPM. The copper in the phase converter is not as stout as the power grid so my simulated 3-phase voltage does move around a bit. When the spindle ramps up the lights on the machine would dim. When the spindle brakes from 5000RPM to zero the lights get brighter as the energy of the spindle and tool dump back to the AC side.
My Bridgeport Interact 4 would randomly get an over or under voltage fault without doing anything too extreme. It wasn't a matter of steady state current because I could load the spindle at 50% all day long. The problem was during a tool change when the spindle would stop and restart. The spindle current would peak 150% of capacity. Since I'm an electrical engineer and am not afraid of finding a solution I tapped into the spindle command voltage from the Heidenhain controller and put a 2 second RC filter in line with the command voltage. Now my spindle takes an additional 2 seconds to ramp up or down. This adds 4 seconds to my tool change cycle but most of the time the machine is not running anyway so what does it matter?
The spindle ramps much more smoothly and will probably prolong the life of everything in the electrical chain.
I wouldn't recommend a rotary phase converter in general because it is an approximation of 3-phase power. A motor-generator setup is going to provide equally spaced phasing of the power legs. The bigger the unit the better. A close matched 3-phase generator setup may result in the same power variations I had with my Bridgeport. I'm currently looking for a 75HP 3-phase generator head that will be used at a gingerly 10HP rate. The peak current in my 15HP rotary phase converter exceeds 60amps on start up. I won't need a prime mover any larger than 15HP due to my total power requirements but I want the copper in the generator to handle peak currents of my machines.
If you can get a single phase machine right out of the chute that would be best. Less time spent worrying about power and more time spent machining.
Dennis
well, I am running a trm (7hp) which fadal built me with a single phase transformer. I decided to go single phase because I didnt want the noise of a phase converter motor running all the time. The machine is in my garage. I understand you lose some power but I have never had any issues with making any cuts or running the machine. I cut mostly allum and a little bit of ss.
Mark
070401-1126 EST USA
fourperf:
Why do you think there is less power available running directly from a single phase line, than if you connect a phase converter to that same line and supply thru this route 3 phase to the machine?
The phase converter is only going to provide minuscul inertial energy storage which is good for only very short transient loads. Also the phase converter has internal losses.
If the phase converter were a synchronous 3 phase motor which means it is also an equally good generator and it had a large inertia load then you could work with longer transient peak loads. This would provide better voltage balancing also.
The other point that I previously mentioned is that running your machine on single phase rather than 3 phase requires a larger capacitor bank for the same ripple level. So not increasing the capacitance would somewhat reduce the maximum steady state power available.
.
Probably what Fadal does when they configure a machine for single phase input is the same as Haas does on the MiniMill and their other small machines that can run single or three phase; use the same rectifier bridge and capacitor setup. This means that the incoming current is limited by the diode rating and the same amount of capacitance is used so there is less ripple smoothing. I know Haas rates the MiniMill at 10hp on three phase and 7.5hp on single phase and the only change bewteen the two inputs is how the incoming line connections are made.
I have been running a 1996 VMC15XT on single phase for about three years. This is the 10HP model. The machine is in my garage and the house has 100 amp service. I had the local Fadal service guy come in and do the conversion. It wasn't much more then taking out a large three coil transformer and replacing it with a single coil unit and then switching some wires around. A couple hour job. They recommended using a 70 amp breaker, but I couldn't find one that large for my panel, so I used a 50 amp. The fuses in the switch box on the machine are 40 amp, so I couldn't see any need for the 70 amp breaker. Machining is a full time job for me and this is my main machine so it sees a lot of hours of operation. In all this time I have never had a power related problem or any conflict with using household appliances (cloths dryer, air conditioner, ect) at the same time the machine is running. I was also told that there would be a HP drop (25%), but that has never been a problem. I recently upgraded the software and can now take advantage of the high torque spindle. Even at extremely low rpm's I have plenty of power.
Good luck,
Herman
Seabrook Machine Company
Mr Magoo; I was wrong, and I am big enough to admit it
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