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ELECTROMECHANICAL DESIGN John Ayers February 23, 2005

ELECTRIC MACHINES . . . . . . . . . STATOR. ROTOR. SHAFT. . . . DC MACHINESSYNCHRONOUS MACHINESINDUCTION MACHINES. ARMATURE POWER WINDINGFIELD WINDING TO ESTABLISH A MAGNETIC FIELD. PRINCIPLES OF OPERATION. MOTOR TORQUE IS ESTABLISHED AS PER THE LORENTZ FORCE LAWGENERATOR VOLTAGE IS INDUCED AS PER FARADAY'S LAW.

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ELECTROMECHANICAL DESIGN John Ayers February 23, 2005

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    3. PRINCIPLES OF OPERATION MOTOR – TORQUE IS ESTABLISHED AS PER THE LORENTZ FORCE LAW GENERATOR – VOLTAGE IS INDUCED AS PER FARADAY’S LAW

    4. DC MOTORS DC MOTOR CIRCUIT MODEL

    5. DC MOTOR CONFIGURATIONS

    6. DC GENERATOR CIRCUIT MODEL DC GENERATORS

    7. 3F SYNCHRONOUS MOTOR ROTATING MAGNETIC FIELD - THE RESULTING MAGNETIC FIELD ROTATES AT AN ANGULAR VELOCITY wM. MOTOR OPERATION – WITH A DC ROTOR CURRENT, THE ROTOR FOLLOWS THE ROTATING MAGNETIC FIELD AND TURNS AT THE SYNCHRONOUS SPEED.

    8. 3F SYNCHRONOUS MOTOR CIRCUIT MODEL (WYE)

    9. STARTING the SYNCHRONOUS Motor

    10. 3F INDUCTION MOTOR ROTATING MAGNETIC FIELD - THE STATOR IS IDENTICAL TO THE SYNCHRONOUS MACHINE. MOTOR OPERATION – ROTOR CURRENTS ARE INDUCED BY TRANSFORMER ACTION. THE MOTOR RUNS AT LESS THAN THE SYNCHRONOUS SPEED.

    11. 3F INDUCTION MOTOR CIRCUIT MODEL (WYE)

    12. OTHER MACHINES STEPPER MOTOR – THIS IS A SPECIAL PURPOSE SYNCHRONOUS MACHINE. THE ROTOR STEPS FROM ONE POLE TO THE NEXT TO ALIGN THE ROTOR FIELD WITH THE STATOR FIELD. MANY POLES ARE USED (FEW DEGREES PER STEP) LINEAR STEPPER MOTOR - SAME PRINCIPLE AS THE STEPPER MOTOR. 1F INDUCTION MOTOR – ACTUALLY AN UNBALANCED 2F MACHINE. “CAPACITOR START” MOTOR. SHADED POLE INDUCTION MOTOR – CHEAP, SIMPLE SINGLE PHASE MOTOR UNIVERSAL MOTOR – LAMINATED SERIES DC MACHINE – CAN RUN ON AC OR DC HYSTERESIS MOTOR – SMALL 1F SYNCHRONOUS MOTORS (CLOCKS)

    13. CHOOSING A MOTOR BASED ON FUNCTION Constant speed / high efficiency – synchronous or induction motor Speed control / high starting torque – DC motor Positioning – stepper motor BASED ON TORQUE and SPEED Determine torque requirement at the load Determine speed requirement at the load Determine and plot the required motor torque versus speed SIZE, WEIGHT, and COST Search for a motor exceeding the minimum requirements but with acceptable size, weight, and cost

    14. CHOOSING A MOTOR BASED ON FUNCTION Constant speed / high efficiency – synchronous or induction motor Speed control / high starting torque – DC motor Positioning – stepper motor or servo motor

    15. CHOOSING A MOTOR BASED ON TORQUE AND SPEED Determine torque requirement at the load Determine speed requirement at the load Determine and plot the required motor torque versus speed

    16. CHOOSING A MOTOR BASED ON SIZE, WEIGHT, AND COST Search for a motor exceeding the minimum requirements but with acceptable size, weight, and cost

    17. Example. The axis of a robotic arm requires 25 ftlb of torque with a minimum speed of 30 degrees/s. Determine the requirement on a DC motor.

    18. Example. A DC motor must drive a shaft in a straight line with 20 lbs force and at 20 cm/s.

    19. DC MOTOR CONTROL

    20. SYNCHRONOUS MOTOR CONTROL

    21. STEPPER MOTOR CONTROL

    22. BIPOLAR STEPPER MOTORS

    23. Sources of Motors jameco.com Emotorstore.com Specialtymotors.com Motorspecialty.com Hundreds of others; see the Thomas Register

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