Re: [CAD_CAM_EDM_DRO] INDUCTION help requested

turbulatordude wrote:

>Hi all,
>
>I have tried reading the posts on the list about Induction and
>searched for some beginners data on the subject, but alas, my
>knoledge has not increased to a working level.
>
>Seems the stepper power supply is based around the induction of the
>motor as are selection criteria of motors......
>
>Yet, it seems that induction is one of the basics we should have a
>working knoledge of in order to make educated decisions.
>
>Can anyone point me to some of the fundamentals ?
>
>

You must be talking about Inductance. That is a property of all
circuits where varying current flows in a wire. When current flows
in a wire, a magnetic field is created. This field stores energy,
just like a battery (well, sort of). When the magnetic field is reduced
(by reducing current in the wire) energy is released from the field back
into the wire. The consequence is that it is harder to raise (or lower)
the current in the wire than Ohm's law would indicate.

When the wire is wound into a coil (thus allowing the magnetic field
to couple between turns of wire, and have a cumulative effect) this
inductance becomes more pronounced. If you put an iron core in it,
it becomes even stronger. The cumulative effect is such that the
inductance follows the SQUARE of the number of turns.
(This is pretty strictly true for iron-core coils, and an approximation
for "air-core" (really, no-core) coils.

This property is very useful for storing energy in power supplies, as
well as isolating circuits that draw current pulses from other circuits.
But, it impedes the rapid rise and fall of current in stepper motor
windings, setting an upper limit on motor speed.

Just do a Google search on "inductance", I got 199,000 hits!

Jon