For controlling the speed of motor braking is done.
It is the most important thing associated with any motor as in case of induction motor braking is done by the following methods:
1) Regenerative Braking of induction motor.
2) AC dynamic Braking
3) DC dynamic braking
4) Zero sequence Braking
5) Plugging braking of induction motor
6) Dynamic braking of induction motor
7) Self-excited Braking
8) DC Injection Braking:
It operates as same as AC operation is done. It is a method of slowing down the induction motor.A DC voltage is applied to induction motor winding, creating a magnetic field which applies torque to the rotor. This will slow and halts the rotor completely. As soon as DC voltage is applied to the windings the rotor stands in its position. DC field in the stator is same as that of AC stator field so it has a frequency of 0 Hz so air gap will be stationary. Higher the voltage applied stronger will be the braking force and holding power. It is basic and widely used for induction motor. The overall effect shows that motor will stop quickly and smoothly. The rotor keeps to be in its place and resistant to any force for a period that the DC voltage is applied. The Strength of the braking force is controlled by DC voltage applied to it. The higher the voltage stronger will be the braking force.
if you need some more information designing this braking system then you can talk to me at
Step 1: DC Injection Circuit Diagram and Video
it can be said that speed torque braking characteristic is image of motoring speed torque curve. If a DC voltage is kept on the stator rotor will be held in its place. If DC injection continues over a period of time it may damage the motor. The DC injection technique can be used for any torque level, it is preferred that small load is braked. DC injection is feature of AC drives today. If DC injection have not applied to the motor then motor would be slow down ,but when the feed is removed it takes long time to stop which may not be acceptable at emergency condition. Maintenance is not increased as braking is provided without the need of touching parts.
in the picture is the simple Circuit diagram i use, in the timer circuit block i use the 555 mono stable to inject DC voltage for few seconds to stop.
Note: how much current is needed to stop the motion of the motor is variable for different motors. , you need to experiment to find the exact ampere required to stop the motor. , as the power used in stooping consumed as heat so frequent stop and start may overheat the motor.
You can see my results in the video above.
These guys really helps me alot in doing this hobby project ,