柳工939FE拖电挖掘机的优点包括：1. 环保节能：该挖掘机采用电动机作为动力源，与传统的内燃机挖掘机相比，无排放、无噪音、无燃油消耗，减少了对环境的污染。2. 经济实用：拖电挖掘机使用电力作为动力源，相比燃油价格较稳定，使用成本较低。3. 高效灵活：拖电挖掘机采用电动机作为动力源，转速快，启动迅速，操作灵活，可以根据工作需求灵活调整挖掘机的转速和力度。4. 无需加油和维护成本低：拖电挖掘机无需加油，同时电动机的维护成本相对较低，不需要经常更换零部件。5. 能量回收：由于拖电挖掘机采用电动机作为动力源，在刹车或者淘汰作业时，电动机可以将能量转化为电能，进行能量回收，提高能源利用率。总之，柳工939FE拖电挖掘机具有环保节能、经济实用、高效灵活、无需加油和维护成本低、能量回收等优点，适用于各种挖掘、土石方、基建工程等工作。

The advantages of LiuGong 939FE tractor excavator include: 1. environmental protection and energy saving: this excavator adopts electric motor as power source, compared with the traditional internal combustion engine excavator, there is no emission, no noise, no fuel consumption, which reduces the pollution to the environment. 2. economic and practical: the tractor excavator adopts electric power as power source, which makes the cost of using it lower compared with the price of fuel, which is more stable. 3. high efficiency and flexibility: tractor excavator adopts electric motor as power source. Electric motor as power source, fast speed, quick start, flexible operation, according to the needs of the work of the excavator can be flexibly adjusted rotational speed and strength. 4. no refueling and low maintenance costs: traction excavators do not need to refuel, while the maintenance cost of the motor is relatively low, do not need to frequently replace parts. 5. energy recovery: because the traction excavator adopts the electric motor as a power source, in the braking or elimination of operations, the electric motor can convert energy into electricity. The electric motor can convert the energy into electricity for energy recovery and improve the energy utilization rate. All in all, LiuGong 939FE tractor excavator has the advantages of environmental protection and energy saving, economic and practical, high efficiency and flexibility, no refueling and low maintenance cost, energy recovery, etc. It is suitable for all kinds of excavation, earthmoving, infrastructure projects and other work.