DVR Science
____________________________
Digital Variable Reluctance Reluctance -- also
called magnetic resistance -- is a property of all
materials, similar to electrical resistance. In some
materials (such as plastic), reluctance is high and it
is difficult to form magnetic fields in them. In others
(such as iron) it's low and magnetic fields form
easily. In those materials where it forms easily, the
charges that generate magnetic flux (the quantity of
magnetism) can be aligned to reinforce one
another and increase the power of the magnetic
field. You can demonstrate this with two permanent
magnets and some iron nails. Align the magnets
North-South/North-South (so they stick to one
another) and you'll be able to pick up more nails
than with a single magnet alone. The reluctance is
lower and the magnetic flux is higher. Now align
them North-South/South-North (so they repel), and
they will pick up far fewer nails than a single
magnet. The reluctance is higher and the flux lower.
____________________________
Digital Variable Reluctance Reluctance -- also
called magnetic resistance -- is a property of all
materials, similar to electrical resistance. In some
materials (such as plastic), reluctance is high and it
is difficult to form magnetic fields in them. In others
(such as iron) it's low and magnetic fields form
easily. In those materials where it forms easily, the
charges that generate magnetic flux (the quantity of
magnetism) can be aligned to reinforce one
another and increase the power of the magnetic
field. You can demonstrate this with two permanent
magnets and some iron nails. Align the magnets
North-South/North-South (so they stick to one
another) and you'll be able to pick up more nails
than with a single magnet alone. The reluctance is
lower and the magnetic flux is higher. Now align
them North-South/South-North (so they repel), and
they will pick up far fewer nails than a single
magnet. The reluctance is higher and the flux lower.
Ordinary electric motors
____________________________
Are like magnetic engines. Permanent magnets
surround an armature with electrical wires wound
around iron plates. Electric current passes through
stationary brushes to a rotating commutator and
into the windings. As the electrical current travels
around the plates, they generate magnetic flux and
a resulting magnetic field. But it just so happens
that the North-South poles in the armature's
magnetic field are opposed to those in the
surrounding magnets. High reluctance develops,
the magnet repels the armature, and the armature
turns so the reluctance will decrease and the
magnetic fields will attract. Unfortunately, the
moment this happens the commutator contacts
switch positions with the brushes, the electric
current reverses direction, and the magnetic field in
the armature plates switch poles -- and the whole
reluctance-flux-north-south-attract-repulse thing
happens all over again.
Back
____________________________
Are like magnetic engines. Permanent magnets
surround an armature with electrical wires wound
around iron plates. Electric current passes through
stationary brushes to a rotating commutator and
into the windings. As the electrical current travels
around the plates, they generate magnetic flux and
a resulting magnetic field. But it just so happens
that the North-South poles in the armature's
magnetic field are opposed to those in the
surrounding magnets. High reluctance develops,
the magnet repels the armature, and the armature
turns so the reluctance will decrease and the
magnetic fields will attract. Unfortunately, the
moment this happens the commutator contacts
switch positions with the brushes, the electric
current reverses direction, and the magnetic field in
the armature plates switch poles -- and the whole
reluctance-flux-north-south-attract-repulse thing
happens all over again.
Back
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Technology
_______________________
Now offers a much better solution. Vary the
reluctance at the same time you vary the
current and you can adjust the available
torque at any speed. You have an electric
motor that can do amazing amounts of work
over a wide range of speeds. Less current
may cause a drop in flux, but decrease the
reluctance and the flux is back where you
need it. The New Zealand company that
developed this motor uses a computer to vary
the current and the reluctance. Select a
speed, and the computer adjusts the current
and reluctance for the motor to run at that
speed with no load. Now require the motor to
do some work -- let's say you're ripping pine.
Power Adaptive Intelligence
_________________________
As you feed the wood into the saw, the
computer senses the load and adjusts the
current and reluctance to increase torque and
maintain speed. You hit a dense knot, the
computer senses increased load and once
again changes the current/reluctance to keep
the speed up. You decide to feed the wood
faster or switch to oak, and the computer
changes the current/reluctance for changing
load requirements to keep the speed
constant. The computer makes thousands of
computations per second, so the saw blade
rarely bogs down even when the load
changes dramatically.
Back
_______________________
Now offers a much better solution. Vary the
reluctance at the same time you vary the
current and you can adjust the available
torque at any speed. You have an electric
motor that can do amazing amounts of work
over a wide range of speeds. Less current
may cause a drop in flux, but decrease the
reluctance and the flux is back where you
need it. The New Zealand company that
developed this motor uses a computer to vary
the current and the reluctance. Select a
speed, and the computer adjusts the current
and reluctance for the motor to run at that
speed with no load. Now require the motor to
do some work -- let's say you're ripping pine.
Power Adaptive Intelligence
_________________________
As you feed the wood into the saw, the
computer senses the load and adjusts the
current and reluctance to increase torque and
maintain speed. You hit a dense knot, the
computer senses increased load and once
again changes the current/reluctance to keep
the speed up. You decide to feed the wood
faster or switch to oak, and the computer
changes the current/reluctance for changing
load requirements to keep the speed
constant. The computer makes thousands of
computations per second, so the saw blade
rarely bogs down even when the load
changes dramatically.
Back
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