| Shield method is widely used in tunnel excavation because of its safety,high efficiency,low labor intensity,small impact on the ground environment and its working schedule is not affected by various external factors.Shield Machine is a large high-tech engineering equipment that is specially designed for tunneling according to the geological condition of tunneling.Cutterhead is the core component of Shield Machine that used for tunneling,which also is one of the key components for Shield Machine.Cutterhead load needs to drive with high power due to its heavy load,sharp load fluctuation and wide speed range.There are 2 main working ways in driving cutterhead so far,one is the hydraulic motor,the other is variable speed motor.By comparing with two ways,cutterhead motor controlled by variable speed motor with frequency converter is a kind of new solution due to high its high efficiency and energy saving.Nowadays more and more Shield Machine cutterheads are driven by variable speed motor with frequency converter.Cutterhead driven by frequency converter become a popular way in the future.The cutterhead load generally shared by 6-14 motors with certain redundancy.In this paper,TBM DZ181 working load has been analyzed based on the typical cutterhead working principle,the cutterhead nominal torque is required for normal working conditions has been calculated out.Equipped motor torque and breakout torque of cutterhead have been calculated furtherly according to the redundancy and extreme working conditions with maximum output torque.DZ181 cutterhead driven by 8×350kW water-cooled motors,thus 8 liquid cooled frequency converter dimensioning has been presented to meet the requirements of cutterhead driving,also heat exchanger has been selected for liquid cooled frequency converter system.The main electrical circuit of cutterhead motor system and the topology of the frequency converter system have been described in this paper.DZ181 cutterhead output torque and power redundency at several typical working speed references have been calculated in detail,the relationship diagram about speed,torque and output power of cutterhead has been worked out,and its constant torque and constant power operating area have been shown in the diagram as well.Based on the maximum load of cutterhead works in extreme condition,the highest overload capacity for transformer has been calculated and maximum intaking current from transformer is recommended for circuit breaker.Multi-motors connect to cutterhead mechanically which needs to make load balancing among motors mainly depends on the speed synchronization of each motor.Master slave solution and paralleled frequency converters control strategy are commonly used to synchronize each motor’s speed and balance the motor load.In this article,through comparing with two kinds of motors control mode,finaly paralleling frequency converter control strategy has been selected,and load dropping function built in frequency converter is introduced to synchronize motor’s speed and load balancing.High temperature,high humidity,dust and vibration are inevitable for Shield Machine due to its underground working ambient,therefore we must consider drive cabinet protection class and solutions related to its operating environmental issues like cooling,heat dissipation,condensation prevention and cooling fluid leakage so on.frequency converter system cabinet solution and periphery components configuration have been presented in detail according to the technical requirements of economical practice.Some key points about cutterhead frequency converter system commissioning and operating issues during commissioning and working stage have been summarized,the corresponding corrective actions have been taken to fix these problems accordingly,which as a good reference for new projects solution. |
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