Induction Motor Design

In article , Gary Pace wrote: [...]

Tesla's works comes to mind :)

You could try googling on XBR and induction motor. You may find the information you need is on line at some university.

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See the ads in Appliance, Appliance New Product Digest, and Appliance Designer magazines.

A quick search finds:

THE INDUCTION MOTOR. ITS THEORY AND DESIGN SET FORTH BY A PRACTICAL METHOD OF CALCULATION. Translation from the French by C. O. Mailloux. De La Tour, Henry Boy. NY: McGraw, 1903

THE PERFORMANCE AND DESIGN OF ALTERNATING CURRENT MACHINES: Transformers, Three-phase Induction Motors and Synchronous Machines. M.G.SAY. London. Sir Isaac Pitman & Sons Ltd. 1948.

Induction Machines: Their Behavior and Uses by Philip L. Alger (first published in 1970)

All those are pre-computer modelling-- more modern work undoubtedly uses computer modelling extensively, along with a whole bunch of proprietary and empirical knowlege. The IEEE IEMDC conference proceedings and vendor list would be a good starting point for access to products and papers in that area. Most recent one was in San Antonio, TX (USA) in May 2005.

But the fastest way to learn in this area is probably to get a job in a company that already does this, which I assume is what you've done, unless your post is a troll.

Best regards, Spehro Pefhany

Actually, induction motors are horribly obsolete.

Because of their difficulty of single phase starting, lousy power factor energy inefficiency, and difficult/limited speed control.

Virtually all newer designs are going switched reluctance instead. The challenges today lie in the cogging and stability algorithms.

Induction motors are infrequently used in the few MW size range where the advantages of synchronous machines are generally significant, but they do have their applications. In these larger sizes it is common to design and build to suit a specific application, normally done by the engineering departments of the few large companies which build motors of these sizes, by a team of experienced mechanical and electrical engineers whom I would expect to be using the latest and greatest in finite element analysis software to deal with the immense complexity of the interrelated thermal, mechanical and electrical issues.

Taking a wild guess that you will be tweaking existing standard designs for some smaller mfgr or merely specifying what exactly you want from a larger mfgr, and assuming you have already read NEMA MG-1, IEEE 115 and the rest of the common motor standards, and that you have a solid understanding of the basic theory which is probably still best explained in Principles of Alternating Current Machinery by Lawrence and Richards (4th ed, 1953) and the generic info in the McGraw Hill Electric Motor Handbook, then you might want to read Analysis of Electrical Machines by Richard Smith.

If your motors will be powered by inverters also look at the new induction motor design by Chorus Motors, which triples low speed torque compared to a standard 3 phase design in the same frame size.

I assume you are talking about small single phase motors such as the appliance motors you refered to earlier. Does anyone make MW sized (well over 1000 HP) 3-phase switched reluctance motors, or is there any reason someone might want to?

Thanks - I'll try to get copies of these.

There are certainly alternative motor technologies that have advantages over the induction motor, I don't think you can say they're obsolete - mature would be a better word. The issues of starting and power factor mainly apply to DOL situations. What other motor technology can connect DOL in any circumstance ?

SR motors have advantages of cheap and robust construction, but present control problems of their own especially in wide speed range torque controlled applications.

DC machines are a very easy control proposition (cheap and robust SCR's), but the (somewhat over-blown) issue of comm/brush maintenance has made them increasingly unpopular.

Synchronous motors have higher power densities and are easy to control. PM machines are problematic to control in field weakening, and sep.ex. motors bring back brushes (or extra windings). These are typically expensive machines.

My experience has been that for most low voltage (or low-end medium voltage) applications below a few MW, a voltage-source inverter (with v/hz control, vector control or direct torque control) and an induction motor is always a good technical and economic candidate.

Glen : Thanks for your reply. I will get copies of all the spec's and books you recommend. No - these are brand new atypical designs.

From reading the various replies to my original post, I received the impression that folks thought it was a troll post (whatever that means) - so here's the background (in case anybody's interested)

We are a manufacturer of motors and drives. I design the drives (IGBT's, DSP's, software, FPGA's, motor control algorithm - all that stuff) and to me, the motors have always been an equivalent circuit with saturation, leakage, resistance etc etc The electro-magnetics of our motors have typically been designed elsewhere, and we've just designed the cooling, selected the bearings, stacked laminates, wound coils, pressed in rotor bars, VPI'ed them...etc etc This is an increasing problem (why is it too hot? why's the power factor bad ?...) so we have decided to find out if we can learn to design motors ourselves in a reasonable amount of time.

Maybe I'll conclude that this is a whole career's work - in which case my next post may well be "who is the best consultant to design the electro-magnetics of our motors" Gary

I have on occasion seen ABB design motors to some customer spec. What they use is a software application that basically generate the input to the mostly robotic factories; and of course generate build-orders to the factory workers that assemble the large machines. You get the delivery schedule documentation and everything of that sort in less than an hour.

It is a *very* mature business.

PS:

Outside the staff cafeteria in Vesteras, Sweden, there is a motor the size of a caravan. The point is that it does not run - but is was built exactly according to the specifications entered into the robotic factory ;-).

so

elsewhere,

bad

Easy: You are not good enough at building motors ;-)

If this is just reasonably standard stuff, why not just drop it and buy the whole thing assembled, tested and ready from one of the large manufacturers?

The motor business is so mature that, I.M.O., there is no way to do better than the COTS stuff.

Um, do you mean, "Caravan", as in "Dodge Caravan", the SUV, or do you mean it's as big as a string of camels and stuff across the desert? ;-)

And, the more important question - _would_ it run, if pressed into service? It's true, there are considerations when scaling stuff, but I've seen pictures of HUGE hydroelectric generators - why not a HUGE motor?

Or is your point that robots are stupid?

Speaking of stupid specifications, I was in on writing a transformer spec one time for a very weird power supply - I don't remember the exact numbers, but this tranny had two secondaries, but it was guaranteed in the spec that only one of them would be used at any time. I was only a tech, but I tried to explain to the PHB, "You don't need to spec the tranny to use both secondaries simultaneously

- you could spec this thing about 33% smaller (or whatever the figure was)" but he overrode me, ordered the oversized transformer, and when it came in, it didn't even fit in the enclosure.

When I showed the guy, "Um, Tom, when I mount the tranny here, I can't put the lid on the box", he was mortified. "OK, it was my goof."

It was strangely unsatisfying. It could have been an "I told you so" moment, but I actually felt pity for the poor dimwit. Oh, well, I guess he's just another example of the PHB syndrome.

Thanks, Rich

All electronic components run on smoke. If you let the smoke out, they do not work any more.

In article , Rich, Under the Affluence wrote: [...]

I think he means what an American would call a "motor home".

It could also be that they applied power too it once and the result was a lot of smoke.

Check that those specs actually apply to you first, MG-1 defines standard sizes, ratings, insulation classes etc. and IEEE Std 115 is motor and generator testing standards per my decade old recollection, but these are US standards which may or may not apply to you.

The McGraw-Hill handbook is probably more useful to motor users than designers.

I first read Lawrence when an electrical designer taking an AC machines course at Drexel University gave me a copy about 15 years ago. His professor, whose day job was designing custom substation transformers, handed them out as textbooks for the course, claiming that it was written by the people who first developed rigorous AC machine theory at MIT, and that nothing written since is nearly as good. I liked it so much I bought used copies of both the first (1916) and fourth (1953) editions, which present an intersting view of AC machine theory development over that period.

Smith goes beyond Lawrence in presenting useful induction motor design theory, taking the approach of "reflecting" (his terminology) stator and rotor currents as well as copper and iron losses "into the air gap", or expressing everything in terms of the air gap magnetic field. I intended to use his equations as the starting point of a motor model a few years ago when I thought I would have time to model the 18 phase Chorus design and have one wound on a standard 36-slot frame, but other priorities have pushed that project somewhere behind the back burner.

Books are cheap, why not look into the one Sphero recommended too.

You are obviously new here. A troll post is usually something like posting 101 things to do with a dead cat to a cat lovers group, but on this group any question from an unknown poster which does not include a schematic, part numbers, design calculations and measurements contradicting those calculations is considered by some to be a troll, inciting a blast delivered in the same spirit as the cat recipe post :-).

Interesting stuff indeed. An alternate question you might ask is who is the best consultant to hire to help get you and your company up to speed on motor magnetics modeling and design. This NG might not be the best place for that question, but the professors who teach AC machines at the few universities which still have a decent power program in their EE department might be a good source of leads. I don't know if MIT still does power or not, but if so they might have their AC machines course available on line too.

BTW I have never designed a motor (although I have tested a bunch of them), just find the subject entertaining. Don't treat my posts as authoritative but as just a bunch of top of the head ideas for you to think about.

Regards, Glen

The box some people drag after their cars the entire summer holiday - mostly to create rolling road-blocks and annoy the hell out of motorists.

Point is that - as far as I remember - the "designer" set the number of poles in the rotor and stator wrong (equal?), so it never starts. It just lets out a gentle hum (until the smoke signals a need of maintenance).

And that the thing went all the way through the build-process on schedule too.

It is also guranteed that regardless of what the spec sez, the two secondaries will be on at the same time eventually - OTOH one sells more product that way.

the bvest way to learn how to do this is by secondment. get your boss to pay you to take a job at, say, WEG, and learn as much as possible. it'll be heaps faster. Or better yet, approach a senior motor designer at one of these companies, and hire him (or her, but odds on its a him).

Cheers Terry

OK, where was that and what did the pump do? 60MW motors (more than one?) would be rather expensive to run for long.