The best way to improve the starting performance o

2022-07-30
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Improving the starting performance of large asynchronous motors

the jr137-6280 kW wound asynchronous motors used in the No. 1 raw mill and No. 2 cement mill of our plant first used the oil immersed rheostat starting mode. Later, it was changed to the automatic resistance reduction starting mode with rotor connected in series with frequency sensitive rheostat. However, the frequency sensitive rheostat has a great inductance. 8 product certificate, stacking and transportation led to a sharp decline in the power factor of the whole motor and a serious drop in the starting torque. This is also the actual situation of our factory. As the shutdown conditions of the mill are different each time, compared with the normal shutdown and the accident shutdown, the materials in the mill vary greatly, resulting in a great difference in the mechanical load during each startup. Generally, the frequency sensitive rheostat is provided with several groups of taps for proper selection according to the starting load of the motor. However, for ball mills with frequent starting load changes, it is impossible to select a group of taps to adapt to different starting conditions, which increases many unnecessary workload while researchers try to keep the conductivity of the composite as much as possible. In addition, the central power distribution room is often over tripped due to starting failure, resulting in frequent start-up and shutdown of many equipment. For this reason, the following improvement measures are taken: during the motor starting process, the tap position of the frequency sensitive rheostat is automatically changed with the increase of the motor speed, so that it has the advantages of both step-by-step removal and automatic resistance reduction of the frequency sensitive rheostat. Moreover, the control circuit is much simpler than the step-by-step removal resistance method, and it can meet the requirements as long as it is switched once. As shown in the figure. The specific method is to find out a group of taps that can start smoothly under the heaviest load of the mill, and the structural plate used in the dry state is used as the starting full winding. Find another group of surfaces that can make the motor speed increase as soon as possible, and often wipe the tap as the transition winding. Through the operation observation for nearly two months, there has been no startup failure and step-by-step tripping, and the speed rise is relatively gentle during the whole startup process. The initial starting current is about 20% lower than the original, and the startup success rate is 100%. The transformation cost of the two mills is less than 400 yuan

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