For application where two drives are coupled on the same drum via gearboxes the master-slave will work.
The Master/Slave solution may face problems in flexible mechanical coupling applications. For example a two motor applications where these are installed on the opposite sides of a conveyor belt. The mechanical link is just the conveyor belt, this represents flexible mechanical coupling.
The Recommended solution is “Droop control” function for the master slave applications. You may refer to  the attached ppt.

Released for:Schneider Electric Ireland