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Thread: Haas VF2SS power requirements
06-07-2007, 10:24 PM #1
Per my last post, we were looking at an SS but noticed they have a serious power requirement of 100A. Our other machines are at 40A so we figured 60A would get it. I know all about the "haas power" spindles so just wondering how much power they would really need at say 125% spindle loads? I realize that a 100A breaker will only hold 80A rms so I am hoping we can cheat this somehow. We may need to bump our power for that machine. Thanks
06-07-2007, 10:57 PM #2
Are you going to run that machine at high load?
The HAAS current rating is probably for 150% spindle load. This load you can not sustain for very long. I am not where I can easily lookup what the HAAS ratings are.
I am not even sure you want or can run at 100% continuous duty.
I assume the 100 A is per leg of a 240 delta source. That is a VA input of about 13.8 * 3 = 41.4 KVA. As a resistive load 55 HP.
If the 100 A, is for 150%, then at 100% your load would be about 67 A.
From the HAAS site this looks like 20 HP at 100% duty. That is about 15 KW. At the moment I can not open the .pdf file.
What is the HP rating you are looking at for 100% duty cycle?
The above figures do not correlate very well.
06-07-2007, 11:50 PM #3
Gar, you sound like a guy I can figure this out with. The thing is I talked to Haas and the machine has an 80A breaker in side so we are already down to 64A rms. I have worked in the electrical field and not too concerned about maxing my sire out as long as things are within "my" safe limits. IA 65A wire and an 80A breaker.
We push our other haas machines around the 140% range at times and hit about 27A. We are using rotary phase converters right now to so input side will be higher because of the split phase. I do not want to build more converter than I need for it because those converter suck SERIOUS power when at idle. Around .35A/hp. That number gets better under power but.
I guess I would not be all smiles if I popped a breaker under load but I can assume that 64A is a min supply for max load on this machine I would think. I would even think that 60A might be just fine all day. Haas has a jacked ass way of working the power numbers. Hell, if you just look at 30hp into amps, it is near 100A.
06-08-2007, 12:16 AM #4
The total power into a balanced 3 phase resistive load is (V/2)* (2/sq-root 3) * I * 3 = (sq-root 3) * V * I .
P = 1.732 * V * I .
V is line to line voltage
I is current in one leg
P is total power in the three equal resistors.
06-08-2007, 02:38 AM #5
Is it possible that there is a fairly serious power spike required whenever all 3 axis rapid at once, considering the high rapid speed, perhaps larger servo drives and motors?
Is the spindle on this one counterbalanced or does it use a large Z axis motor instead?
06-08-2007, 02:41 AM #6
I too am getting a VF-2SS and am as confused as you are Viper. More, actually, since I'm pretty much clueless about electrical stuff. I hope you don't mind me butting in your thread here.
Sellway said that the 80A breaker in the machine is a "slow burn breaker" if that means anything to you.
06-08-2007, 02:50 AM #7
Well all breakers have a curve relative to amps over time. Most breakers cannot exceed 80% of rated continuous. Anything over that will be rated in the curve before it pops. The slow burn should still pop over 80% but hold out longer before doing so. That being said, I have not heard of the slow blow breaker so I will have to look into that.
Gar, I am just real confused as to how Haas calculates power. You are qouting specs for resistive loads. Shouldn't we be refering to inductive loads or is this because of the power VFD supply before the motors? I am seriously doubting that any real calcs will be accurate on the haas since they seem to over advertise there power as I understand it.
06-08-2007, 04:22 AM #8
I'm very interested in what you find out Viper. Mine is going in my garage and will be running off an American Rotary 50hp phase converter, and they say I need to supply 200A single phase if the machine needs 100A three phase. Ugh. If that's true, I'll need to install a second 200A panel and I really wanted to avoid having PG&E come out. The machine will be here in about two weeks.
06-08-2007, 10:09 AM #9
From my experience, machine tool builders overrate the electrical requirements by almost double. I would bet 50A service would run the Haas just fine.
The Japanese builders started this overrating stuff years ago. Conservative bastards.
I have (temporarily) 2 Mazak QT15's and 1 Mazak VTC16B running off the same 50A circuit. Never been a problem. But, if I went by Mazak's ratings, I would need well over 200A total to run these 3 machines. Go figure.
06-08-2007, 01:57 PM #10Gar, I am just real confused as to how Haas calculates power.
Rev up the motor on a test bench, clamp down on the output shaft until it stalls out, and read the PEAK amperage rating before bursts into flames, convert that amperage into HP, multiply it by 1.5, then stick a giant red sticker on the side of the machine proclaiming, "30HP Vector Drive!"
I'd imagine your 60 amp circuit will be just fine. It's just like when I plug my "7.5HP!" Shop Vac into a 15amp wall socket.
06-08-2007, 02:15 PM #11
Is there any short or long term damage to a modern CNC mill if you have a breaker trip? What I'm getting at is if you run this thing off a 50A breaker (100A in my case with the phase converter), what's the worst that can happen?
06-08-2007, 03:27 PM #12
My reason for providing a resistive load calculation is because I can accurately define it, and it provides information on the maximum possible power from a 3 phase source at a defined current.
At 240 V line to line and a line current of 100 A you can not get more than 41,568 watts from your load. In the case of a motor it will be less. In this calculation it is assumed the waveforms are sinusoidal and voltage and current are the RMS values.
Form a single phase 240 V source you will need 173 A assuming 100 efficiency to obtain the same power.
This sets an upper bound.
There are two factors that determine your power source needs. One is voltage regulation, and the second is not overheating the source.
Consider a standard 20 A circuit with #12 wire. At a 15 A load I will not overheat the wiring or breaker at 70 deg F. But at the end of a 1000 ft run (2000 ft of wire) (approx 1.6 to 1.9 ohms/1000 ft) we have a voltage drop of 3.8 * 15 = 57 V. If this was on a 120 V circuit it would probably be intolerable.
06-08-2007, 03:55 PM #13
I guess I might have to role the dice or wait for Matt to test his out. We are going to be pushing the limits here so I guess we may have to keep an eye on the load meter.
06-08-2007, 04:20 PM #14
If you know that you will push the limits on a continuous basis, then you have to worry about the thermal rise within your spindle and servos.
Get a voltmeter and Amprobe and find somebody with a machine, HAAS dealer, and run a sample part under the conditions you expect and see what the results are. The current on each leg many not be quite the same, but should be close at full load because a large percentage of the power goes to the spindle.
06-08-2007, 04:35 PM #15
the limits I was refering to was my lack of power for the machine. We may have to just reduce our heavy cuts until we can get more power or at least see what it will really need. fun though that 100A should be required for a true 30hp spindle but we know better.
06-08-2007, 04:51 PM #16
I would strongly suspect that since this is an SS model, the higher current rating is for the rapids, but, more importantly the spindle accelleration.
Lower rated wiring might be OK, or not. Consider how much voltage sag you will see when the spindle tries to go from 0 to 12,000 rpm, in three seconds. (whatever the numbers are)
The S machine was modified for rapid spindle start stop, fast tool changes, and faster rapids.
The amount of power needed for the axes will not be nearly as significant as starting and stopping the spindle.
IF nothing faults from low voltage on spindle starts, you might get away with it.
Any consideration about max cutting loads might not be the issue. Weather the wiring heats up during the three second (actual time??)spindle start might not be the issue.
Sagging the voltage to the control, or to the drives might be the issue.
You notice that the actual power ratings of the machine is not a lot higher than the non S model, but they do have a higher current rating. bigger wiring will not have as much droop for an inrush current as "adequate" wiring.
06-08-2007, 05:34 PM #17
I will sure be testing inrush on spindle starts first thing. I will probably oversize the wire and undersize the breaker to allow minimal voltage drop. I agree it is probably rated as is just for the start up. We will have 240V three phase from the converter so we should be on the high side of the voltage window so I am hoping that will further decrease it's need for current.
06-08-2007, 08:27 PM #18
Just a data point guys: I just got back from a new shop in town with a VF-3SS, a mini mill, a super mini mill and a small-ish CNC lathe, all running on the same 100A breaker. No phase converter, but still. All four machines were running when I got there (he runs them pretty hard too) and he reports no problems in 3 months.
I'm gonna try a 100A breaker on the single phase side and see what happens.
06-08-2007, 10:15 PM #19
Put an ammeter in your single phase line and set your own criteria on how heavy to load the line. Maybe 70 A steady state will allow reasonable peaks. It will be a function of how large and long the peaks last.
A thermal breaker or fuse has an inverse time characteristic. Also when a breaker is near full rating for a moderate time this shortens its time to trip on a given overload.
06-08-2007, 11:18 PM #20
Thanks Gar, I'll do that when my machine shows up in two weeks. [img]smile.gif[/img]