Sliver
Member
The application is on a ball mill inching drive.
The current setup uses a 75hp 575V 1800 rpm motor to position the mill for lining up the access doors for removal and mill entry.
The procedure is to engage an inching 'clutch' which meshes in the forward direction only and drive the 4800hp sync mill motor to align the doors a certain distance past top dead center. The balls in the mill then are all piled up on the forward side and to relieve the stored energy the mill is allowed to roll back through a friction brake that needs to be released in a very controlled manner to prevent overspeeding the inching drive.
This procedure is very tricky the first few times and if the stored energy is not properly released, we have had the mill shift by 6" or so with people inside. They were not happy.
A suggestion has been forwarded from another plant that uses the inching drive motor to control the roll back. Once the mill is rotated past the position required the motor is reversed (they use reversing starter) and the motor acts as a brake to bring the ball charge down to the bottom in a controlled fashion.
My question is if the drive has the tourque to push the load does it have the ability to hold back the overspeeding torque?
What would happen if the backspinning motor was allowed to accidently freewheel for several seconds before the reversing power was applied? If we lose the motor on fuses or overloads then you would have to be quick on the manual brake I think before the motor and reducer explode.
Anyone see or hear of a setup like this?
thanks,
Brian.
The current setup uses a 75hp 575V 1800 rpm motor to position the mill for lining up the access doors for removal and mill entry.
The procedure is to engage an inching 'clutch' which meshes in the forward direction only and drive the 4800hp sync mill motor to align the doors a certain distance past top dead center. The balls in the mill then are all piled up on the forward side and to relieve the stored energy the mill is allowed to roll back through a friction brake that needs to be released in a very controlled manner to prevent overspeeding the inching drive.
This procedure is very tricky the first few times and if the stored energy is not properly released, we have had the mill shift by 6" or so with people inside. They were not happy.
A suggestion has been forwarded from another plant that uses the inching drive motor to control the roll back. Once the mill is rotated past the position required the motor is reversed (they use reversing starter) and the motor acts as a brake to bring the ball charge down to the bottom in a controlled fashion.
My question is if the drive has the tourque to push the load does it have the ability to hold back the overspeeding torque?
What would happen if the backspinning motor was allowed to accidently freewheel for several seconds before the reversing power was applied? If we lose the motor on fuses or overloads then you would have to be quick on the manual brake I think before the motor and reducer explode.
Anyone see or hear of a setup like this?
thanks,
Brian.