Download The Switched Reluctance Motor

The Switched Reluctance Motor
©2012 Dr. B. C. Paul
Note – Concepts presented here in are considered common knowledge in the field and are
found in numerous texts no one of which was intentionally copied. Figures are from various
sources including “computer simulation technology”, Texas A+M University, Electric Motorbike
Inc, Hearst Electric Products. List may not exhaustively site all locations where similar figures
may be found.
The Switched Reluctance Motor
The Stator contains
3 electro-magnets
powered by DC
Current.
The Rotor is a Plain Piece of Steel
capable of carrying a magnetic flux
The rotor is connected
To a shaft that is it
hoped will turn to
make something
happen.
The Path of Least Resistance
• Water will follow the path of least resistance
• Electricity will follow a path of least resistance
Magnetic Reluctance
• Magnetic flux likes to find an easy flow path
• A nice piece of steel is a much better flow path than air
• The magnetic flux will try to get the steel path to line up (considered
magnetic reluctance)
Making the Motor Work
If I keep turning magnetic fields off
And on around the stator I can
Have the rotor continuous chasing
The magnetic field and thus
Turning the shaft –
I now have a DC motor with no
Rings or brushes. (But one wholly
Heck of a lot of switches)
Problems
• The torque the motor produces is proportional to
where the rotor is relative to the poles
• The effect is highly non-linear
• As the rotor chases the poles the poles the
torque ripples up and down
Try This
A bunch of extra poles and then let a project logic controller program do the field
Switching to smooth out the torque.
Of Course
• We have just created a motor that depends on a
bunch of solid state switching technology and a
computer to be able to operate
• That would have been a big deal in 1912, but not
2012.
• Its still a big deal if I’m talking ½ hp motors, but if I
need a big torqueing motor a computer controlled
motor is another story.