A variable-frequency drive (VFD) is a type of motor drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and, depending on topology, to control associated voltage or current variation. VFDs can be used to control AC motor speeds by changing the motor's frequency without sacrificing the output power of the motor. This is done by turning the speed pot (explained in section three) of an AC motor drive.


So using the means of VFD dragging three-phase induction motor replaces the means of traditional speed regulating, can solve the problem of high failure rate of the tower crane fundamentally. Moreover, it has advanced technology and significant energy saving effect. It is the ideal transmission controlling device of the tower crane.




