Energy Consumption Characteristics And Key Energy Saving Technique For Electrical Machine And System With Periodical And Potential Load Conditions

Electric motors and systems with periodic potential load generally have heavy and light loads as well as motor and generator modes during a running cycle.Due to the dynamic load conditions and complex operation conditions,it is difficult to develop a universal energy saving technology for this type of load.For the typical periodic and potential load,this dissertation establishes the comprehensive energy consumption analysis model and reveals the related loss characteristics,and then develops the intermittent supply energy saving technology which is suitable for the periodical and potential load.The key problems during the power-off control and rapid re-switching process are also studied systematically.The main contents of the dissertation are as follows.1.For beam pumping motor system which is a typical periodic potential load,a comprehensive energy consumption model is established which takes into account the loss of all components in the system,such as the induction motor,the mechanical link,the transmission line and the transformer;and the variation of the loss components with the dynamic liquid level and the balance degree is revealed.Based on the theoretical analysis,the energy saving mechanism of intermittent supply control and the key problems during the power-off control and the rapid re-switching process are analyzed.2.To deal with the motor systems with unknown parameters and longer running cycle,a fuzzy control based power-off time determination method is proposed,which takes the speed extremum error as the input variable and the power accumulating value as the output variable.To deal with the motor systems with given parameters and shorter running cycle,the relationship between load torque and crank angle is revealed,the range of motor speed variation and the energy saving ratio can be calculated,and the suitable speed range and optimal energy saving can be determined as the accurate power-off time.3.In order to realize the soft and rapid re-switching in the intermittent supply control,in the respect of the re-switching time selection,a method for determining optimal re-switching time is proposed.With this method the torque-speed characteristic of motors can match the requirement of load torque after power-off control.In the respect of soft and rapid re-switching control,the dissertation proposes the determination method of firing angle and the related control strategy by which the motor electromagnetic torque can match the load torque immediately during the re-switching process.4.By comparing the characteristics of different energy saving technologies of electrical motors and systems with periodic and potential load,a universal energy saving approach with the intermittent supply as the core technology is proposed by integrating wye-delta dynamic conversion,multi-tap voltage regulation and reactive power compensation.The coordinating strategy of the above technologies is determined,and the corresponding energy-saving controller is developed.A significant energy saving ratio is achieved in the practical application of the proposed technology at oil fields.