Marine cranes are divided into two types of driving methods: electric cranes and electro-hydraulic cranes.

Electric cranes

Electric cranes have high efficiency, correct speed regulation, easy operation, minimal maintenance, and easy remote control. There are two commonly used types of electric cranes: generator motor system and thyristor control system. The former adopts a three-output mode, which supplies power to the lifting, variable amplitude, and rotary motors respectively. It has the advantages of fewer motors, smaller volume, and smaller installed capacity while retaining the characteristics of good starting and speed regulation performance of DC motors; The latter is superior in terms of maneuverability, efficiency, and scale, and this form of heavy-duty electric crane is gradually being used on large ships. Its lifting capacity series is 5-40t, with a maximum working radius of 12-36m.

Hydraulic/electro-hydraulic crane

The operation of electro-hydraulic driven cranes is smooth, lightweight, small in size, step-less speed regulation, and has the characteristics of constant power, high-speed empty hook, and slow heavy load. Due to the continuous improvement of hydraulic technology and the use of electronic control, while maintaining the advantages of electric cranes, electro-hydraulic driven cranes have been widely adopted.

The electric motor hydraulic pump group inside the crane tower is driven by one electric motor to drive three hydraulic pumps, which respectively drive the hydraulic motors or hydraulic cylinders of the lifting, variable amplitude, and turning mechanisms. High-pressure electro-hydraulic drive cranes usually use axial piston hydraulic pumps and hydraulic motors. The transmission mechanism of the winch is planetary gear transmission, and it is installed inside the winch drum together with a hydraulic motor, with a compact structure. There are two forms of variable amplitude mechanism: hydraulic cylinder and variable amplitude winch. Medium-pressure electro-hydraulic drive cranes often use vane pumps and hydraulic motors or high torque low-speed hydraulic motors.

The lifting capacity series of electro-hydraulic driven cranes is 5~50t, with a maximum working radius of 32m. The lifting speed at full load is generally around 12m/min, and for high-speed models, it can exceed 20m/min. The empty hook speed is usually twice that of full load; The rotational speed is generally around l r/min and varies with the floating state of the ship; The variation time from the maximum working radius to the minimum working radius is approximately 1 minute.

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