Tower crane and gantry crane differ, the work of the power system to a large extent determine its safety and reliability and performance , so the tower crane electrical system to meet the following requirements . First , with good speed performance Because the role of space tower crane is relatively large, so only meet the relatively high operating speeds in order to meet production requirements, but the rope taut CDD Electric Chain Hoist before lifting positioning and installation , but also require a steady slow pace , avoid excessive impact and it is difficult to reduce accident hazards. Therefore , tower cranes speed performance is extremely important to have enough speed range. Second, with repeated short-term work system to adapt to frequent start , brake, and positive and negative direction of movement requirements. Third , the load characteristics of each organization is different , there is a tower crane CDD Electric Chain Hoist, slewing , luffing , running , erection, lifting, cable reel and other institutions , the load characteristics of great distinction institutions . For example, the lifting mechanism for the potential energy load , lifting load unchanged for the constant torque ( load torque does not change with the speed of change ) , when rising resistance load , load time decreased as the driving force ; swing , run and level luffing agencies The main transfer horizontal loads , such as wind , friction slope. Starting and braking, to overcome the inertia of the larger , wind resistance and inertia which accounted for most of the resistance , and resistance to the randomness of these two big , big changes in nature and size of the load . Erection and installation of lifting bodies belonging to the load characteristics of the installation concerned . Load characteristics of the different , the choice of motor speed control method to determine the transmission program and , operation and other aspects also have different requirements. Fourth , transfer, unloading and installation of frequency more frequently.