DC Motor Lecture Notes

Introduction to DC Motors

• DC motors convert electrical energy into mechanical energy.
• Used in various applications, from small home devices to large industrial machines.
• Different types of DC motors exist, but they all operate on the same basic principles.
• For detailed classification, refer to another video on the topic.

Working Principle of DC Motors

• When supply is given to field and armature windings:
  • Both windings create magnetic fields.
  • Interaction of these magnetic fields causes the armature to rotate.

Understanding Electromagnets

• Example using magnets:
  • Same polarity magnets repel each other.
  • DC motors use electromagnets instead of permanent magnets.
• Creation of Electromagnet:
  • Random electron dipoles in a metal piece align when current flows through a coil.

Basic Model of a DC Motor

• Two metal pieces are energized to become electromagnets:
  • One becomes N-pole and the other S-pole.
  • A magnetic field is established between them.
• A copper loop placed in the magnetic field:
  • Connected to a commutator and brushes.
  • Brushes are linked to the DC supply.

Force on Current-Carrying Conductors

• Current in a magnetic field experiences a force.
• Fleming's Left Hand Rule:
  • First finger: direction of magnetic field.
  • Second finger: direction of current.
  • Thumb: direction of force.
• Current direction changes as rotor moves, affecting magnetic polarity.

Torque and Inertia

• Torque is created when magnetic polarities repel each other.
• Inertia keeps the rotor moving until the current direction changes again, causing continuous rotation.

Components of a DC Motor

• Armature contains multiple loops of wire:
  • More loops provide smoother rotation and higher torque.
• Field winding and armature winding must both be supplied:
  • Creates a constant magnetic field.
  • Interaction of fields leads to rotor motion.

Summary of Operation Sequence

1. Supply power to field and armature windings.
2. Current flows, generating magnetic fields.
3. Interaction of magnetic fields creates repulsion, rotating the rotor.

Conclusion

• Understanding the interaction of magnetic fields is crucial for the operation of DC motors.
• Additional resources and videos are available for further learning.