As a kind of crane, tower crane has lifting mechanism, trolley mechanism and slewing mechanism.

The special feature of the converter of tower crane is that it is used to lift the potential energy load, with large impact and inertia. The starting torque and safety requirements of the converter are very high. The other is to input three-phase power, and then the inverter is converted into DC with IGBT. According to the different gear and speed, according to the electrical formula of V / F = constant, the voltage is reduced by duty cycle to realize variable frequency and variable speed. F is the frequency, which can be understood as the motor speed. According to the increase of speed, the output voltage V increases approximately linearly, and different speeds are obtained.

The frequency converter is composed of three parts: input power circuit for power supply, output power circuit for motor, braking circuit for braking unit and braking resistance, input control circuit for speed gear, reset and other control signals. Speed signal has three modes of digital quantity, analog quantity and bus. Generally, encoder feedback is added to lifting; output control circuit is connected with relay and indicator light to indicate inverter status state

Lifting generally uses a special crane setting software called lifting macro, which is different from translation mechanism.