The Switched Reluctance The Switched Reluctance MotorMotor
©2012 Dr. B. C. PaulNote – 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 The Switched Reluctance MotorMotor
The Stator contains 3 electro-magnets powered by DC Current.
The Rotor is a Plain Piece of The Rotor is a Plain Piece of Steel capable of carrying a Steel capable of carrying a
magnetic fluxmagnetic flux
The rotor is connectedTo a shaft that is it hoped will turn to make something happen.
The Path of Least The Path of Least ResistanceResistance
• Water will follow the path of least resistance• Electricity will follow a path of least resistance
Magnetic ReluctanceMagnetic 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 WorkMaking the Motor WorkIf I keep turning magnetic fields offAnd on around the stator I canHave the rotor continuous chasingThe magnetic field and thusTurning the shaft –
I now have a DC motor with noRings or brushes. (But one whollyHeck of a lot of switches)
ProblemsProblems
• 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 ThisTry This
A bunch of extra poles and then let a project logic controller program do the fieldSwitching to smooth out the torque.
Of CourseOf 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.
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