Application Of Variable-frequency Speed Regulation System In Tower Crane

Most of tower cranes use multi-speed or wound rotor electric motor to regulate their speed of mechanism. This way has many disadvantages. It can not obtain enough lower speed at the start-stop to debase shock pulse and vibration which may induce hit accidents. The electric motors have complex constitution such as brush gear or slip ring which needs maintenance and repairing. The electric control system contains many contactors and relays frequently closing and opening. This may result electric parts damaged because of large pulse current. To improve the traditional speed regulation in tower crane is required.Variable frequency speed regulation technology combined with PLC is one of the best ways to improve the performance of tower cranes. The AC inverter provides sufficient protection such as over-heating, over-current, over-voltage, under-voltage, open-phase etc. The inverter can set parameters by digital operator display or input terminal, and provide several control methods such as close loop vector, open loop vector, V/F with or without PG. The inverter supply with S curve acceleration or deceleration, dwell functions and droop control .These can provide tower canes lower arrival speed, small shock pulse, zero speed braking, simple wire connecting, energy saving, and high reliability.The article introduces the application of the inverter in tower crane's lifting, trolley, and slewing mechanism in mode of vector control or V/F, and illustrate with figure. Compared with traditional tower crane control system, variable frequency speed control has advantages in safe, reliability and energy saving.