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Universal Motor

Universal Motor. Universal Motor. Series-connected Rotor and Stator are connected in series Operates on either ac or dc NEMA ratings 0.01hp – 1.0hp @ 5000r/min or above. Equivalent Circuit. A Closer Look. Field Winding Field (Stator) . Armature (Rotor).

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Universal Motor

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  1. Universal Motor

  2. Universal Motor • Series-connected • Rotor and Stator are connected in series • Operates on either ac or dc • NEMA ratings • 0.01hp – 1.0hp @ 5000r/min or above

  3. Equivalent Circuit

  4. A Closer Look Field Winding Field (Stator) Armature (Rotor)

  5. The Commutator Bar and Brushes are a switch that reverses the current in the armature coil as it rotates

  6. Check the Direction of Rotation Flux “Bunching” Force on conductor B is upwards, rotation is counter-clockwise (CCW) +Positive Half-Cycle+

  7. Opposite Half-Cycle Flux “Bunching” Force on Conductor B is upwards, rotation is counter-clockwise (CCW) -Negative Half-Cycle-

  8. Conclusions • The direction of rotation (and Torque) is independent of the polarity of the AC source! TD = Developed Torque Bp = flux density due to current in field Ia = armature current

  9. Other Considerations • How do you reverse the direction of rotation? • Reverse the direction of the current in either the field or in the armature, but not both! • How do you control the speed of the motor? • Reduce the voltage applied to the motor • Use an autotransformer or SCR/Triac • This reduces the armature current, reducing the torque, reducing the speed • Applications • Portable power tools • Small appliances

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