Top Drive System : A top drive is a big motor system which is hoisted in a derrick or mast of a drilling rig. A top drive is a modern rotating system which has been popular for many drilling contractors and oil operators. Top drives can be used on all types of rigs, from truck-mounted rigs to offshore rigs. Rotation provided to a drill stem is accomplished by a top drive. Therefore, a Kelly and a Kelly bushing are not required for a top drive system. Moreover, a master bushing and a rotary table