I am using a 310VDC, 4pole BLDC motor with hall sensor feedback for my application. My objective is to run the BLDC motor at 7500 rpm. My motor rated speed is 8500rpm. I am able to run motor at 7500 rpm now. My other objective is to stop the motor within 1 second period from 7500 rpm. I am using BLDC drive as my own design. Now I am able to stop motor within 5 seconds. I am not able to reduce the above stopping time. Help me with the methodology to stop within one second period. Input supply of my BLDC drive is 310V.
Are you able to accelerate the motor from 0rpm to 7500rpm in one second? If not you will not be able to perform the reverse action in that time.
It may very well be time to consider why you believe you need to stop in one second. This level of performance may not be possible with the motor, load and type of drive electronics that you are using.
A more normal operational scenario would be to anticipate ahead of time when you need to stop the motor and then start the deceleration curve at such time that the 0rpm condition occurs at your needed stopping point. You could compare this to operating your car. As you are approaching a red light at 50kph you do not keep up that velocity until you are right on top of the intersection. Instead you anticipate the need to stop and start braking well before the intersection.
Finding the characteristics of your system and learning what maximum acceleration and deceleration are possible is part the tuning study that needs to be done during the design and development phase. Proper selection of the motor, power system and driving subsystem are all part of this process.
Your requirement is pointing to a mechanical brake of some sort. Look at motorcycle or other automotive practice depending on your power level (unstated) and the momentum of your driven system.
For an extreme example of a mechanical braking system, see Sawstop with a braking time of 5 milliseconds.