Reversing the direction of an across-the-line AC motor is as simple as swapping the connection between any 2 motor leads.  However, reversing a motor run by a vector drive with encoder feedback requires reversing the motor leads AND one encoder channel.  The motor leads and encoder feedback must be kept in phase or the vector drive will not run properly.  In a vector drive it is usually better to reverse rotation using the drive software than by reversing the motor and encoder wiring.