I don't like your chances about keeping the inductance the same. A lower
voltage for the same amp-turns means higher current and less turns.
Inductance is proportional to the square of the number of turns (until
saturation) so 1/2 the turns, results in 1/4 inductance.

As it's a solinoid and I'm guessing you're looking at running it from AC if
you're concerned about inductance. The stauration level will change
according to the position of the solinoid so there may be some sort of
sweet spot but it's going to be difficult to optimise.

Can you run it from DC? Then the inductance is less important and it's
simply DC resistance and number of turns (i.e wire guage) to worry about.
And switching spikes and possibly slower drop out and/or sticking as the
poles get magnetised. Running at different votages (PWM)  for pull-in and
hold-in may be an option but is an additional complication. If there's a
spare pole on a sense switch, you could achieve the same by switching in a
(burden) resistor to reduce hold-in current. Give it pleanty of ampere
turns to pull in and switch down to enough current to hold in (with flat
batteries?).

RP

On 22 April 2015 at 08:13, David VanHorn <microbrix@gmail.com> wrote:

> Some things seem to get harder to find as time goes on.  Things like this
> used to be done all the time, probably from paper nomographs that never g=
ot
> enwebified.
>
>
> I have a solenoid coil that I'd like to re-wind from 120V to 12V.
> The complication is that I need to keep the amp-turns and the inductance =
to
> similar values.
>
> The original is 70 ohms, 19 layers of 176 turns or 3344 turns.  I wasn't
> able to measure the inductance due to high series resistance.
>
> Seems like this should be possible, and yet I've found precious little in
> data on how to rewind for different voltages.
>
> I tried re-winding for amp-turns and had limited success, but the output
> energy was very limited.
>
> The device in question is a BD-10AS from ElectroTechnic products.
> The magnetic field of the solenoid opens a switch which is integral to th=
e
> function, and so I need about the same level of flux.  I am theorizing th=
at
> the reason for low output was the lower inductance of my 400 turns of #19
> vs
>
> I need to use it far from an outlet, and powering it with an inverter is
> almost certainly going to result in a smoked inverter. I thought of a
> series pack but the idea of a battery at 120V with any real output curren=
t
> is pretty scary.
> --
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
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