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Induction Motor Design

Discussion in 'Electronic Design' started by Gary Pace, Oct 1, 2005.

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  1. Gary Pace

    Gary Pace Guest

    Howdy Y'all :

    Somewhat OT.

    I am going to start designing induction motors (flux density, rotor bars,
    pole faces, stator slots, insulation systems etc etc) up to a few MW at
    various voltages and frequencies

    I've been controlling them for decades, so I know a bit about this.

    Does anyone know :

    - Any good books on this subject
    - A better newsgroup to ask

  2. Ken Smith

    Ken Smith Guest

    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.
  3. Guest

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

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  5. A quick search finds:

    METHOD OF CALCULATION. Translation from the French by C. O. Mailloux.
    De La Tour, Henry Boy. NY: McGraw, 1903

    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
  6. Glen Walpert

    Glen Walpert Guest

    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

    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.
  7. 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.

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  8. Glen Walpert

    Glen Walpert Guest

    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?
  9. Gary Pace

    Gary Pace Guest

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

    Gary Pace Guest

    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

    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.
  11. Gary Pace

    Gary Pace Guest

    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"
  12. 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.


    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 ;-).
  13. 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.
  14. Terry Given

    Terry Given Guest

    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).

  15. Ken Smith

    Ken Smith Guest

    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?[/QUOTE]

    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.
  16. Glen Walpert

    Glen Walpert Guest

    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

    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

    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.


  17. 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.

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

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  18. 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
    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.
  19. I read in that Glen Walpert <>
    Well, not ANY question. The troll-detector does tend to respond to
    people who post the equivalent of, 'I don't know anything about
    doctoring, so please tell me which web sites show me how to be a brain

    Usually less well spelled and less gramatiqual.
  20. I read in that "Rich, Under the Affluence"
    'Caravan' is British English for 'trailer'.
    I've been close to some 60 MW motors at a water pumping station (3300 A
    at 11 kV 3-phase), quite big but I don't suppose they are the biggest.
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