Written pole motors

This U.S. company says they can make larger single phase motors up to 75 horsepower. I was wondering about the good and bad points of
this. http://tinyurl.com/24c92bs
Thanks.
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Looks ALL GOOD to me.

You are welcome.
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IF claims are as stated. How does the stator adapt to the necessary conditions without some sort of feedback control? It appears to be a variation of previously existing PM motor technology. It may be very good but, surely, on the basis of the reference- there is no more than PR handwaving.
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snipped-for-privacy@shawcross.ca wrote:

Just looking at the numbers in the table under 'Benefits of Technology' (page 3), there are some discrepancies. For the conventional 3-phase motor, the power doesn't work out right for a 0.85 power factor. Nor does the stated kVA.
If the technology's valid, I can see a niche market were you need a low-starting current motor. But it seems like the added complexity would result in a higher price for 'average installations'.
daestrom
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I "explored" the company's website.
There was an interesting instalation up in Wisconsin or Michigan in an irrigation application.
The farmer worked with the power company to help select the motor. The power company knew it couldn't give the farmer 3 phase power nor could it tolerate excessive start up currents.
The farmer and the power company were pleased with the installation.
To address one objection, YES it requires a lot of extra "control" equipment. In the process of starting to being close the full speed the number of magnetic poles changes ("written poles") on the fly. The controls have to be propected from the elements and this alone makes it more of a PITA to install.
The company also sells a version of the technology by which it uses the high mass of the rotating parts to provide continues power during "blink outs" of the utility power. Apparently, as the rotor slows down the output frequency can be maintain by re-writing the poles. It can maintain power long enough to start a diesel generator!
In another application of the base technology, it can create 3 phase power from a single phase feed.
Like any other piece of technology, every application has to be "costed out" and compared to alternatives.
Obviously, the primary applications are in "middle of nowhere" places (farms, mines) where the power company isn't willing to bring in unlimited three phase power but "significant" loads exist. It can be quite cost effective compared to running a medium sized (30 hp or so) diesel engine. Compared to an IC engine, this system is "maintenance free." The energy savings can pay for the investment in about a year for a near 24/7 operation.
I only have "dial up" so I didn't download the high resoluton stuff but those of you that do might want to surf the site.

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John Gilmer wrote:

On the surface this sounds a lot like the old repulsion-induction motors. Wasn't low starting current one of the big advantages of those?
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Perhaps.
It's best you explore the site.
This is a "something else" motor. The rotating part seems to be the shell (like in a ceiling fan motor.) There is a layer of "medium hard" ferite material on the incide of the shell. As as the "written pole" implies, the system can create poles on the fly. The poles have the spacing and number to let the motor operate efficiently at much less than "sync" speed. The electronics seems to incorporate a variable frequency multiphase power supply plus what ever it takes to write/erase the poles.
The "shell" design with the motor a HECK of a lot more inertia than your basic squirel cage or even a wound rotor machine. Ordinarily, of course, that's doesn't help anything. But they have turned lemon into lemonsaide by making it into a UPS!
As I understand the design, there are no wearing parts outside of the bearings so it might be somewhat more rugged than a wound rotor machine. OTOH, once up to speed, it's a "permanent magnet" motor. These CAN pick up tiny pieces of steel.
Because of my low speed ISP, I didn't see the detail diagrams and pictures.
Like I said, like anything else you have to "price it out." It's practically made to order in an irrigation application where once started the load is essentially constant. But the technology doesn't seem to be suited for a deep well pump.
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I have been involved in testing some of these as well as applying them in the field. They do work. The downside? More expensive, more complicated.
Charles Perry P.E.
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Charles Perry wrote:

Can one make any educated guesses about durability? I was thinking of the irrigation application mentioned by John Gilmer. Irrigation well motors generally sit outside. They are usually in the 50 to 75 hp. range in my area. They get hit by blowing dirt, crop dust, precipitation, and whatever else the wind can carry. Lightning, and air temperatures ranging from about -20F to over 100F are part of the deal.
Thanks
Dean
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I know of units that have been in the field for over 10 years. I have not heard of any reliability issues.
Charles Perry P.E.
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