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# Re: [femm] Scaling question

- To: rtickle@visi.com
- Subject: Re: [femm] Scaling question
- From: Renuka Rajput <renuka@cat.ernet.in>
- Date: Fri, 16 Feb 2001 11:03:47 +0530 (IST)
- Cc: femm@yahoogroups.com
- In-reply-to: <96ibd2+ac74@eGroups.com>

    First of all I have doubts regarding scaling down the original design by
    1/4 and also some suggestions for that.
    (1). Are you scaling down the whole magnet, including the core width, core
    height, pole width, pole gap, Ampere-turns in the coil etc?
    (2). Generally while making the quartre scale(or some other scaled)
    prototype of a magnet only the length of the magnet is scaled down.
    (3) If you are even scaling down the coil parameters by 1/4, then you are
    bound to get 1/4 fields as can be seen even by simply using the formula
    for field of a dipole magnet.
    (4) Whatever scaling you want to do, first you must check by the simple
    analytic formula about the field values for sclaed down current density
    values, then only you should go for femm nanalysis.

    I can help you in this (if you need so), for that please send me
    your detail requirement and scaling factors etc.

    Renuka Rajput
    *************************************************************************
    Dr.(Ms) Renuka Rajput
    Scientific Officer
    Beam Physics and FEL Lab
    Centre for Advanced Technology
    P.O.CAT, INDORE - 452 013 (M.P.)
    India
    Phone (Off.) - 91 - 731 - 488020/488018
    (Res.) - 91 - 731 - 489829
    Fax (Off.) - 91 - 731 - 488000
    *************************************************************************

    On Fri, 16 Feb 2001 rtickle@visi.com wrote:

    > Question for David and group:
    >
    > I've modelled a simple C core type electromagnet with two sets of
    > coils in femm based on a design we are considering building. We are
    > looking at building a quarter scale prototype first to make sure we
    > can produce the fields the numerical solution tells us we can. I've
    > noticed however, that in scaling down the original design by 1/4 and
    > recalculating in femm, much smaller fields are produced in the
    > airgap. Only by multiplying the original current density by 4 are the
    > original fields of the full scale model produced along the centerline
    > of the airgap. I had assumed that I would want to keep the current
    > density fixed while scaling the model down; the numerics seem to be
    > saying this is wrong. Can anyone explain why this is so?
    >
    >
    >
    >
    >
    >

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