A pole changing type squirrel cage motor used in derricks has four, eight and twenty-four poles. In this, the medium speed is used for
Right Answer is:
A crane is a type of machine, generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. Lift speed is usually based on the height the product will be lifted, the frequency of lifts, and how delicately the product must be set down (this can also be accomplished with 2 speed or variable speed).
This means that if you are lifting a near-capacity load with a 30-ton crane, the crane will operate at a nominal speed (medium speed) and, once the hook is empty, will return at a faster speed to pick up the next load. This increases your crane’s average speed and reduces average hoist cycle time to raise productivity in a given work period.