Modifying Three Phase Motors For Single Phase Use?
Some time ago I saw an article or a posting on a way to modify a three phase motor by reconnecting the leads somehow that makes the motor easier to start and run on single phase power. I THINK I saw it here. This modification does NOT make the motor a single phase motor. I think it required a 12 lead motor to work, and the connection was not a simple delta or wye. The concept was named after the inventor, whose name I am also drawing a blank on, or so I recall (e.g., the "Johnson Motor").
I did searches here with any and all terms I could think up, all to no avail. At the time I saw the article or posting, I thought, "gee, that's neat", and bookmarked it or saved a PDF or something, for future use. Unfortunately, that computer has gone to computer heaven and I no longer have the information.
Can anyone help me out here? I am working on a machine that has an extremely built-in 440V only three phase 1HP motor on it. I pulled the field with the idea of reconnecting for 220V and was pleasantly surprised to find the splices very conveniently located. I can probably bring out all 12 leads if it will help but I won't unless I can find the information on the modification mentioned above.
Just in case I've got the wrong end of the stick I'll keep this brief.
You need to connect your motor Delta.
Connect your supply to two of the phases.
Connect the other Phase to the line with a capacitor - the value depends on the motor rating.
The motor will start OK if it's unloaded. However, if it has any load you will need to switch in extra capacitance to get it going. My Chipmaster witha 3hp motor requires 100 uF to run but an extra 500 uF to start up.
I can Post diagrams.
static phase converters
That's exactly what a "static phase converter" does.
Originally Posted by AlanBeckett
It's not really a phase converter at all, in the sense of an RPC which actually generates voltage.
It's just a motor starting circuit with a detector that disconnects the capacitor from the third leg automatically when the motor gets up to speed.
Google "Phase-A-Matic" to find static converters.
Thanks, Leigh and Alan, but that ain't it. I'm familiar with shifting capacitance in to start a motor, rotary converters, VFD's etc, and this is something different. I really can't recall too much about the specifics but I'm sure the completed motor isn't self-starting on single phase.
By the way, Alan, here in the states we don't always have the option of connecting motors delta as, I would guess, a vast majority of older motors (older motors for older users) are permanently connected wye at what you are probably familiar with as wires numbered 10, 11, and 12. All we have to work with are wires 1 through 9.
In my case the motor is permanently connected wye single voltage 440. That's why I plan to delve into the internal connections on the stator, at the very least to connect for 220 or, if i can find the info on this modification, I'll bring all 12 leads out.
the search continues!
I think I know what you are referring to. But I think what you have forgotten (or never fully was made aware of) was that this required a very precisely tapped transformer ahead of the motor, then later he or someone else came up with an IDEA of using another motor as a "rotating transformer" in the same way. However it meant essentially tapping into the windings of the motor at a precise spot etc. etc. etc., something well beyond the skills of any but the most accomplished of motor technicians. I had kept details on it on an old PC, I'm not sure if I still have it. You are right though, it was widely discussed in here, maybe 4 or 5 years ago, before everyone at the time came to the conclusion that the skill set necessary to pull it off was beyond what most people are capable of. Besides, it turned out to be a lot more trouble than just using COTS phase adder technology.
Originally Posted by sa100
I'll snoop around for it in my old HDD and see if I can come up with a search-able name reference.
Found it faster than I thought.
I think you are referring to the H-A-S system. With this system you would need a 12 lead wye wound motor connected in a certain way thru a static phase converter, with this setup there would be no hp loss. I think it is made by Steelman Industries.
Thanks for the comments and the link. You are right, this sounds way too complicated for mere mortals and is certainly not something I'd consider trying. On first glance the link is mostly hoopla and hype but out of curiosity I will try to learn a bit more about what exactly he is doing.
You smack dab nailed it. "Steelman" is the name I was trying to remember. The whole thing looked complicated when I first saw it and it still looks complicated now. But now I at least have the information to go over until I understand it. Looking at the PM link you provided, I remember exactly looking at the hand drawn diagrams you made. I'm off on another errand right now but I will study this a little later. Don't be surprised if I have questions.
Thanks to both of you!
And now, because I can't help myself, a bit of a rant that doesn't really have anything to do with the matter at hand.
I never realized until I started frequenting this site just how common it is for large, credible businesses to use three phase converters. I had thought this was pretty much the realm of hobbyists and small-beer operators. My reaction is, we Americans as a people sure are dumb. Look at the Germans - they have three phase in every home, or so I am told. I seriously doubt any businesses there would resort to phase converters. We should have demanded the same long ago!
Yes, that is my thread from about three years ago.
While originally designed for a motor-generator-type Monarch 10EE, either 230 or 460 volts, the approach is also applicable to many other machines, particularly those which employ a NEMA-type magnetic motor starter, and also reversible machines which employs a reversing motor starter.
The design has been independently verified on a stand-alone motor which was operated into a "prony brake" measuring system, and the conversion did indeed produce 100 percent of motor nameplate horsepower. In fact, slightly more than nameplate horsepower was measured.
This, with the machine (or the motor under test) operating from a single-phase motor feeder.
The conversion for a 10EE is particularly appropriate for residential use, but it could also be appropriate for a Series lathe in a residence.
At one point, I was seeking to upgrade my shop to a 13 x 42 or 13 x 54 Series lathe.
The adaptation of my design for the reversing motor starter in a Series lathe is straightforward. You reverse the main winding using the motor starter's L1/T1 and L3/T3 terminals. The motor's starting/quadrature winding uses the L2/T2 terminals.
Henry A. Steelman's inventive device is in use in rural agriculture irrigation and oilfield recovery applications in many places where three-phase services are unavailable.
Originally Posted by sa100
An H.A.S.-type conversion operates the load motor as a capacitor start/capacitor run motor.
Originally Posted by The real Leigh
Its not in any way like a conventional "static", which can only produce about 2/3 of nameplate horsepower.
I enclose some information I have on a way to use Three Phase Motors on a Single Phase Supply, its called a Steinmetz Connection.
I hope this will be of interest.
Re: your rant...
There is a BIG difference here. It has nothing to do with anyone being "dumb", it has everything to do with basic economics.
Originally Posted by sa100
The entire land mass of Germany would fit inside the state of Montana with wiggle room around the edges. Running 3 phase power out to every household in the US would require 33% MORE copper wire than currently used for that purpose (4 wires instead of 3 from every pole) which would likely bankrupt the power utilities.
"... its called a Steinmetz Connection ..."
It's still a static converter of the type first disclosed in an IEEE journal by Haberman in the late 1940s or early 1950s.
Ah, that one.
Originally Posted by Jraef
A friend of mine built and uses it over here and swears by it. I've sourced a big three phase transformer so I can have a go.
"Running 3 phase power out to every household in the US would require 33% MORE copper wire than currently used for that purpose (4 wires instead of 3 from every pole) which would likely bankrupt the power utilities."
Residential single-phase requires three conductors (L1, N and L2).
Three-phase generation, transmission and subtransmission requires three wires (A, B and C).
Most three-phase distribution also requires three wires. Exception: those original delta distribution systems (A, B and C) which were "wyed-up" and which require four wires (A, B, C and N).
At the very large electric utility (also this Nation's largest municipal electric utility) where I was an EE in a former lifetime, we had NO company-owned systems which were NOT delta, hence all of our generation, transmission, subtransmission and distribution was delta and, hence, was three wires.
Possibly the only cases of four wires was an occasional 4160 wye customer, but in these cases the customer was provided with either 4.8 kV or 34.5 kV, at our option, and he provided the 4.8 kV or 34.5 kV (delta) to 4160 (wye) transformer and vault at his own expense.
Last edited by peterh5322; 01-03-2011 at 03:38 PM.
You can run a 440 volt motor from single phase by using a step up transformer (single phase) and a 440 volt VFD that will accept single phase input. Most Asian VFDs will work this way. it is practical for motors up to 2.5 hp or so. The VFD needs to be rated for twice the load motor horsepower. We have discussed this many times in the past.
I've found the step-up and VFD combination to be practical at 10hp. The transformer starts to get big and heavy, but one of the things I'll eventually incorporate into my 'new' shop building, will be a large 240-480 single-phase transformer and a 480v single-phase panel to my shop tools... because my overhead crane will be running off of 480-single feeding VFDs... and it's kinda hungry.
3 phase Conversion
I'll send you the PDF showing the connection you are looking for. It's from an Industrial Electrical journal from 1984. Similar to Haas/Steelman. Maybe it will help. It's too big to attach.