Introduction to motors


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Introduction to motors

  1. 1. Motor construction • Rotor • Stator • Air gap • Windings
  2. 2. Parts of DC Motor
  3. 3. Series Motor Advantages of DC series motors: • Huge starting torque • Simple Construction • Designing is easy • Maintenance is easy • Cost effective
  4. 4. Permanent Magnet DC Motor • Higher efficiency since no electrical energy is used or losses incurred for developing or maintaining the motor’s magnetic field. • Higher torque and power density. • Linear torque speed charcteristics. that are more predictable. • Better dynamic performance due to higher magnetic flux density in air gap. • Simplified construction and essentially maintenance-free. • More compact size.
  5. 5. Advantages simple torque and speed control without sophisticated electronics
  6. 6. General Torque Equation Translational (linear) motion: dt d JT   Rotational motion: dt dv MF  F : Force (Nm) M : Mass (Kg ) v : velocity (m/s) T : Torque (Nm) J : Moment of Inertia (Kgm2 )  : angular velocity ( rad/s )
  7. 7. Synchronous Machines
  8. 8. • Above a certain size, synchronous motors are not self-starting motors. This property is due to the inertia of the rotor; it cannot instantly follow the rotation of the magnetic field of the stator.
  9. 9. • synchronous motor produces no inherent average torque at standstill, it cannot accelerate to synchronous speed without some supplemental mechanism.
  10. 10. Applications • Synchronous motors are especially useful in applications requiring precise speed and/or position control. • Speed is independent of the load over the operating range of the motor. • Speed and position may be accurately controlled using open loop controls, e.g. stepper motors. • Low-power applications include positioning machines, where high precision is required, and robot actuators. • They will hold their position when a DC current is applied to both the stator and the rotor windings. • Increased efficiency in low-speed applications (e.g. ball mills).
  11. 11. Induction Motor • Asynchronous motor • AC electric motor
  12. 12. Introduction • Three-phase induction motors are the most common and frequently encountered machines in industry
  13. 13. Induction Motor • The electric current in the rotor needed to produce torque is induced by electromagnetic induction from the magnetic field of the stator winding. • Does not require mechanical commutation
  14. 14. – simple design, rugged, low-price, easy maintenance – wide range of power ratings: fractional horsepower to 10 MW – run essentially as constant speed from no-load to full load – Its speed depends on the frequency of the power source • not easy to have variable speed control • requires a variable-frequency power-electronic drive for optimal speed control