In Today`s lecture we are going to study about the Dynamic Braking of 3 Phase Induction Motor,In the last two lectures we studied about the Regenerative Braking and Plugging Braking,you can get there note from the electrical drive menu.
Dynamic Braking are of four type:-
1.AC Dynamic Braking
2.Self Excited Capacitor Braking
3.DC Dynamic Braking
4.Zero Sequence Braking
इसी ब्लॉग को हिंदी में पढ़ने के लिये यहाँ :-क्लिक करे
In this lecture we will first talk about the AC Dynamic Braking.
1.AC Dynamic Braking:-So Friends in AC Dynamic Braking we remove the one phase of supply from the motor and we left removed motor lead open or connect with any other of the two remaining connected phase supply.The Former case is known as Two Lead Connection and the later is known as Three Lead Connection.Let see the image to understand it more..
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| Fig 1.AC Dynamic Braking |
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| Fig2. Stator Diagram During AC Dynamic Braking |
Friends here we can see that Ic=-Ib and the same magnitude and direction of current will flow in coil B and C and that will be positive for one half cycle and negative for the other half cycle.Now the famous rotating magnetic field will no longer exist and a pulsating magnetic field will be created that will give rise to a pulsating torque in the rotor which will be in the same direction of rotation for one half cycle and opposite direction for the next half cycle.
It is found that opposite direction torque is much higher when the rotor resistance is higher so extra resistance is added to the rotor through slip ring and brushes.Opposite direction torque brakes the motor.This method is best utilized when the load torque is lower than the rated torque because of inertia.
Disadvantage-In this process it become the single phasing of rotor and high heat and noise is produced.It also adversely affect the lifetime of the machine.
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