Plugging braking of Induction Motor(English)

Hello friends today in this blog we are going to discuss about the Plugging Braking of Three Phase Induction Motor.

Friends as in case of DC motor we were applying the plugging braking by changing the polarity of the power supply to the motor similarly in this case of three phase Induction Motor we are going to change the phase sequence of the three phase supply to the motor.

इसी ब्लॉग को हिंदी में पढ़ने के लिए यहाँ :-क्लिक करे  
Change of the three phase sequence of the motor can be achieved by interchanging any of the two connection of the three phase supply to the motor.

When we change the phase sequence of the motor the famous rotating magnetic field changes its direction of rotation and a torque is created in the negative direction of the rotor because of the induced current in the rotor.

In this way motor de-accelerate and come to the rest at this point supply must be disconnected otherwise motor will start to rotate in the opposite direction.

The slip in the case of plugging can be given by-

Sn=2-So

here Sn is the new slip(Braking slip)

and So is the old slip(normal slip)

Lets see the image to understand it more-

As we can see that in normal case rotor rotation speed(Nr) and the Rotating Magnetic field speed or synchronous speed(Ns) are in the same direction and Nr always try to catch with Ns,that is why the relative speed is the difference of the two.

In case of the braking,Nr and Ns are in the opposite direction that is why the relative speed are the addition of the two.  

Advantage-This the fastest method for braking than any other.

Disadvantage-

In this method because the relative velocity of rotor and the magnetic field is large so a high fluxed is linked with the rotor resulting in very high current.It produces very high heat and sometime it may melt the rotors bars.

So it is not used normally but can be very good for the urgent braking.