Electric Motor | working of DC Motor


Electric Motor

The electric motor may be a device which converts electricity to energy . There are mainly three types of electric motor.

  • DC Motor
  • Induction Motor
  • Synchronous Motor

All of those motors add more or less same principle. The main function of electric motor depends on the magnetic flux with current. To understand this topic better we will discuss the essential operating principle of electrical motors one by one.

Working of DC Motor

Working principle of DC Motor mainly depends upon Fleming left rule. In DC motors, an armature is placed between the magnetic armors. If you armature winding is supplied from an external DC source. So the armature starts to conduct current through conductors. As the conductors are carrying current inside a magnetic flux , they're going to experience a force which tends to rotate the armature. If the armature conductors move downward (in cross) under the N poles of the world magnet. And others below the S poles move the current upwards (in dots).By applying Fleming's left-hand rule, the direction of force F is experienced by the conductor below the N poles.

And the force experienced by the conductors under the S-poles is determined. It is found that at any instant the forces

Series Dc Motor

experienced by the conductors are in such a direction that they have a tendency to rotate the armature. Again, due this rotation the conductors under N-poles come under S-pole and therefore the conductors under S-poles come under N-pole. When the conductors become n-poles from s-pole and s-pole to n-pole. So the direction of current through them is reversed through the commutator.   Due to this reversal of current, all the conductors come under N-poles carry current in downward direction and every one the conductors come under S-poles carry current in upward direction as shown in the figure. Each conductor comes in the same direction due to the N-pole experiences force. And the same holds for conductors under the S-pole. This process helps with developing constant and indirect torque.  

Working of Induction Motor

Working of electrical motor within the case of induction motor is small bit different from DC motor. In single phase induction motor, when one phase supply is given to the stator winding, a pulsating magnetic flux is produced and during a three phase induction motor, when three phase supply is given to 3 phase stator winding, a rotating magnetic flux is produced. Induction motor rotors are either wound type or squirrel like paper.  

The induction Motor is a self started motor

Whatever could also be the sort of rotor, the conductors thereon are shorted at end to make closed-loop system . Due to rotating magnetic flux , the flux passes through the air gap between rotor and stator, sweeps past the rotor surface then cuts the rotor conductor.

3 phase induction motor

Hence consistent with Faraday’s law of electromagnetic induction, there would be a induced current circulating within the closed rotor conductors. The amount of induced current is proportional to the speed of change of flux linkage with reference to time. Again this rate of change of flux linkage is proportional to the relative speed between rotor and rotating magnetic flux . As per Lenz law the rotor will attempt to reduce the every explanation for producing current in it. Hence the rotor rotates and tries to realize the speed of rotating magnetic flux to scale back the relative speed between rotor and rotating magnetic flux .

Working of Schronous Motor

In electric motor , when balanced three phase supply is given to the stationary three phase stator winding, a rotating magnetic flux is produced which rotates at synchronous speed.    

Working of synchronous motor

Working of Synchronous Motor   Now if an electromagnet is placed inside this rotating magnetic flux , it's magnetcally locked with the rotating magnetic flux and therefore the former rotates with the rotating magnetic flux at same speed that is at synchronous speed.


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