What is the Principle of a Motor

Motor Principle

• An Electric motor is a machine which converts electric energy into mechanical energy. Its action is based on the principle that when a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force whose direction is given by Fleming’s Left-hand Rule and whose magnitude is given by F = BIl Newton.
  
• Constructionally, there is no basic difference between a d.c. generator and a d.c. motor. In fact, the same d.c. machine can be used interchangeably as a generator or as a motor. D.C. motors are also like generators, shunt-wound or series-wound or compound-wound.
  
• In Figure a part of multipolar d.c. motor is shown. When its field magnets are excited and its armature conductors are supplied with current from the supply mains, they experience a force tending to rotate the armature. Armature conductors under N-pole are assumed to carry current downwards (crosses) and those under S-poles, to carry current upwards (dots).
• By applying Fleming’s Left-hand Rule, the direction of the force on each conductor can be found. It is shown by small arrows placed above each conductor.
• It will be seen that each conductor can be found. It will be seen that each conductor experiences a force F which tends to rotate the armature in anticlockwise direction.
• These forces collectively produce a driving torque which sets the armature rotating.
• It should be noted that the function of a commutator in the motor is the same as in a generator.
• By reversing current in each conductor as it passes from one pole to another, it helps to develop a continuous and unidirectional torque.