EC-12.3 Energy Conversion, and DC and AC Machines

Work through these

• The two laws that make every machine work

  A current in a magnetic field feels a force, and a conductor moving in a magnetic field develops a voltage. Both act in every machine at once, which is why the same device can motor or generate.

  NPTEL: Electrical Machines (IIT Delhi) · Course

• The direct current machine, and what the commutator is for

  A rotating winding in a fixed field would produce alternating voltage. The commutator reverses the connection twice per turn so the external terminals see direct current, at the cost of brushes that wear.

  NPTEL: Electrical Machines I (IIT Kharagpur) · Course

• Speed and torque control in a direct current machine

  Torque follows the current and speed follows the applied voltage, with the field strength scaling both. That independence is why these machines dominated variable-speed work before electronics could match it.

  NPTEL: Electrical Machines I (IIT Kharagpur) · Course

• The rotating field, and the induction motor

  Three windings fed by three phases produce a field that rotates at the supply frequency. The rotor is dragged along behind it, and the difference in speed is what induces the rotor current that makes torque.

  NPTEL: Electrical Machines (IIT Delhi) · Course

• Slip, and the torque against speed curve

  At the field's own speed the rotor sees no change and makes no torque, so it must run slower. The curve of torque against speed explains starting current, the peak torque and why the motor settles where it does.

  NPTEL: Electrical Machines (IIT Delhi) · Course

• The synchronous machine, and the grid

  A rotor carrying its own field locks to the rotating field and turns at exactly supply speed. Nearly all generation is synchronous, and its excitation is what sets the reactive power it supplies.

  NPTEL: Electrical Machines I (IIT Kharagpur) · Course