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10-27-2010, 07:35 AM #1
220 vs 440 and phase conversion questions
I am a newbie and found this forum last night. I have an 18 yr old son who is in his last year of machine tool tech program. We are setting up a small machine shop in our door yard. We have an Excelo Mill and Med size Cincinnati lathe. Mill is 1 1/2 hp and lathe is 3 hp. Both machines are dual volltage 220/440. We have no three phase in our neighborhood. We have an Hitachi electronic converter that came with the mill but don't like it. We are looking at rotary phase converters. Would like to know the pros and cons, based on ease of operation more than just cost.
Since the phase converters I have looked at would require a transformerto step up to 440v, would it make more sense to use the 220 windings in the motors and simplify things.
Question my son asked me last night and I don't know the anwer to is this: Is there any advantage to using the motors on 440 v as opposed to 220?
Appreciate any advice.
10-27-2010, 08:09 AM #2
Since you do not have three phase power available, reconnect the motors and controls to run on 220 volt power supplied by a VFD. Being unhappy with the VFD may be it is not set up correctly for the system. I have individual VFD's on my Lathe, Milling machine and Surface Grinder and all run on 240 volt single phase input power.
10-27-2010, 10:33 AM #3
The advantage of 440 over 220 is the amount of current the wires will have to carry. The higher the voltage, the lower the current. Power used will stay the same.
But as JR said, get a VFD and rewire your motors for 220. Check the amperage rating on the motors - make sure the VFD can handle it i.e. - will he be running both machines at the same time?
Is the Hitachi a Variable or Static converter? The Variable type gives you some neat capabilities for speed control
However, you may need a Rotary Phase Converter if your loads are too high.
There is a section in this forum here with lots of info -> Transformers, Phase Converters and VFD - Practical Machinist - Largest Manufacturing Technology Forum on the Web
10-27-2010, 02:23 PM #4
The advantage of running on 440 will be negated by the power losses running through a transformer. I would just run them on 220 with a rotary phase convertor. There are very good plans on here to build a rotary phase convertor. Which basically consists of a three phase motor, some capacitors and a start and run circuit. I built my 5 HP phase convertor for under $200 by picking up a good used motor and electrical panel that had most of the components I needed.
10-27-2010, 09:41 PM #5
I run the Hitachi VFDs. Set up correctly they function perfectly on a mill... It now feels "odd" when i use a mill without the VFD braking.
10-28-2010, 07:28 AM #6
Thanks for all the good info. I worked as a machinist in my earlier years. I worked in a boat yard machine shop and thoroughly enjoyed it. Got away from it later on to work in other areas of construction. My son has been interested in it for years and is an outstanding student. He is interested in eventually doing some small manufacturing of, particularly, firearms parts and hot rod/automotive items. He will probably go to work in a shop someplace nearby but is very interested in having his own place someday, even if he works mainly by himself. He has his parents independant streak I guess.
I am enjoying all of this thoroughly as it will give us a bit of being able to work together on something we both enjoy.
The shop I worked in had 3 phase but I was never involved in hookups, I just ran the machines. I am not familiar with phase converters at all as I have no experience with them. It does make sense to me to run the motors on the 220rather than the 440 for simplicity sake. I do understand the smaller wire issue with the higher voltage. I am just not familiar with the converters at all.
The Hitachi we have, L200, has the variable speed feature. I am sure some of our apprehensions are because we are unfamiliar with them. Is this a popular unit? We have the machine so it starts and runs but have not actually tried milling anything yet. My son is afraid of damaging the motors on these machines if something should go wrong and can't get by that.
We are stuck on rather to buy another electronic phase converter for the lathe or go with the rotary and sell the electronic one we have. I am reading all that I can find, and am still uncertain which is best for us. Money is a definite consideration but we don't want false economy just to save a few bucks up front and have to spend more later. If we do the rotary we would be looking at only running one machine at a time.
The Cincinnati lathe is 15 x 48 which is big enough for what he wants to do. It is older but in pretty good shape. Has a 3 hp Fairbanks motor. Would there be any problem running it with an electronic phase converter?
10-28-2010, 07:40 AM #7
once you get used to the VFD you will love it. that is probably a 2 hp unit, so it is not big enough for your 3 hp lathe. You can buy these new for 200 dollars or so, so I suggest getting one for the lathe and keeping the one on the mill. This is an ideal set up. One under used feature is dynamic breaking, where you can program your stop times, soft starting is annother important feature, especially when using residential wiring, since it prevents the power surge during start up.
My 2 cents
10-28-2010, 08:06 AM #8
I have an L200 on one lathe.. it's OK, but the L200 isn't my first choice... it is only "volts/hz" rather than "Sensorless vector", but more importantly (IMHO), it doesn't have the capability (without spending $$$$) of adding external braking. The external braking does more then "brake" - it allows you to keep your DC buss voltages under control when you have high rotational masses - like a chuck or big work... (your motor becomes a generator). The end result is the vfd goes off-line to protect itself. By programming B131/132 (and a few others) you can work around this somewhat, but not perfectly.
I use the Hitachi SJ200 series and the Teco 7300 series.
Hmmm... if you're not into VFD fiddling (it can be daunting for some) and multiple machines, then you may well be better off with one decent size rotary converter for the shop. Rather than a 3 phase breaker panel on the output, all you need is to wire a fused disconnect at each machine.
10-28-2010, 11:20 AM #9
Having run machines on static phase converters for years (and rotaries here and there too) and now on a VFD....I think the vfd blows the phase converter off into the weeds for any machine that just has a motor.
If the machine has multiple motors, and or other electronics that require 3 phase I understand wanting to use a rotary phase converter...but otherwise....screw that flintstones crap ;-).
There are some killer deals, or were on used 440 vfd's that had some people buying transformers to step up to 440 from 220.
10-28-2010, 11:44 AM #10
Sorry I wouldn't use a static phase convertor on anything, as it basically jump starts the motor then single phases which is very hard on the motors. I have not had one problem running off of the rotary phase convertor I built that is why i recomended it. You can run multiple machines from a rotary without a problem as long as it is big enough to run them all. I am not familar with converting from single phase to three phase with a VFD (variable frequency drive?), How does that work?
10-28-2010, 11:52 AM #11
Again, the 'electrics and phase converters' sub-forum has much information on this
Suggest it be perused.
10-28-2010, 01:54 PM #12
I ran in my home on a static converter of the type that generated a third phase with capacitors for years and later on a rotary when I moved into my shop. Both worked, but neither developed full power in the lathe and mill they supplied. There is a company that sells rotary converters they promise to give accurate three phase. Out of curiosity, I called them and tried to find out how they did it. I verbally chased the guy around for 20 minutes without getting a real answer. Either he didn't know or it is a secret.
Just to be clear, some static converters work like the starting winding on a split phase motor, just deciding which way to start as MrT says, and others, like the one I had, effectively run the machine motor in the same manner as the rotary converter motor. You don't get full power either way, although the second type delivers more. The first type really sucks. Nothing beats a real three phase line. It took few years of badgering the electric company, but I finally got one.
10-28-2010, 02:03 PM #13
Thank you, so these are basically the same as any other invertor drive just configured to produce the third phase.
10-28-2010, 03:50 PM #14
When my son got home we put some stock onto the mill, fired it up with the L200 and took a few cuts. It worked real well. So we feel OK going ahead and getting one for the lathe. Its a 3 hp motor. Any model recommendations for Hitachi, or other, that would work well on this late?
When we bought the mill, the man we got it from told my son to be careful not to turn the speed too high or too low as that could harm the motor. Any truth to that? And why?
10-28-2010, 04:44 PM #15
take a look at Drives Warehouse.
10-28-2010, 05:30 PM #16
"There is a company that sells rotary converters they promise to give accurate three phase. Out of curiosity, I called them and tried to find out how they did it."
Very very well, here's the rotary:
Here's what it does:
And here is how it was measured:
10-28-2010, 05:43 PM #17
10-28-2010, 07:10 PM #18
Presumably that is a single phase motor driving a three phase generator. Of course, that was one possibility, but this dude would not confirm anything or give a meaningful answer to a question. I don't know why they should be so secretive because any customer could look inside and figure it out. I ran across such a rig that I should have gotten. A friend is active in Stray Rescue. A major stock broker gave them a former office building, leaving several pieces of equipment, which my friend asked me to identify. One was a 240 three phase synchronous motor coupled to a 120/208 generator, puzzling at first, until I considered that the office was full of computers. By running them off the generator they protected them from lightning strikes and in a momentary power loss it would coast, keeping them from losing data instantly. Later, it occurred to me that it would make a good phase converter by running one phase of the motor from a condenser, which some of my friends could use, but I could never get through to the person who would make a decision regarding disposal.
Something else I probably should post on the converter forum is running the output of a rotary converter through a three phase transformer connected in wye-delta so the energy to any output phase would come from all the input phases. A broken star-delta would mix them up even more. I have brought it up on this forum a couple of times, but there was no response.
10-28-2010, 09:20 PM #19
That's just a 3 phase motor with a pony start.
10-28-2010, 09:30 PM #20
The Hitachi will quite happily take your motor to 400% of its rated speed... don't go there... apart from having no torque at the top end, it can literally fly apart.
I would not use an L200 for the lathe - Lathe and mills have different characteristics (rotational masses); use an SJ200, install braking resistors, and program it accordingly. If you're not into VFD's, this may entail a lot of frustrating head scratching.