The Best Towards Polarity Exciting Study Of Synchronous Motor's Asynchronous Starting

Synchronous motor is widely used in fixed-speed drive system of industrial production, which has the advantages of adjusting power factor freely, fixed speed, and hard load property etc. Synchronous motor's starting mainly adopts asynchronous starting method, e g. make use of damp windings to asynchronously drive motor to a speed approximate to synchronous speed, then choose a certain time to exert exciting current to pull into step. This method is much more convenient and low-costing than auxiliary motor starting and frequency conversion starting, however, exerting exciting has always been a difficult problem in asynchronous starting, synchronous motor suffers a lot from strong vacillation, large stator current impact, and long time of pulling into step, even can not pull into step in heavy load condition after exerting exciting, which causes adverse influence to motor itself and power grid.At present, synchronous motor's exciting generally adopts rotor-electricity towards polarity method, which takes advantage of the rotor-inductive voltage, produced in the process of asynchronous starting, to judge exciting speed and exciting time, but the rotor-inductive voltage becomes rather weak when synchronous motor's speed approaches synchronous speed, therefore, it is quite common that synchronous motor can not be excited or excited in error under great disturbance condition of industrial producing. And the best towards polarity exciting method for synchronous motor's asynchronous starting put forward by scholars both in home and abroad in recent years is also hard to realize in rotor-electricity method due to its short-comings of rotor-inducted signal, hence, acquiring of the exciting signal aims to stator side.In this dissertation, the best towards polarity exciting area is ascertained through comparing exciting curve of different exciting time by simulation which was carried out by mathematic simulation software of MATLAB, and a best towards polarity exciting method by stator-electricity without rotor position detector is put forward, which singly detects and analyzes stator's current wave through software to get motor's speed and catch the best towards polarity exciting time. Debugged through in experimenting board cored with TMS320C2812 digital signal processor (DSP). The result of the experiment demonstrated that this method has good reliability, short pulling time and low impact, it is correct and effective, largely solved the problems existing in synchronous motor's asynchronous starting exciting. Furthermore, the configuration and design method of synchronous motor's microprocessor exciting system are introduced, as well as digital PI regulator and microprocessor shift-phase triggering principle.The best towards polarity exciting method by stator-electricity without rotor position detector put forward in this dissertation is a new type method for synchronous motor's asynchronous starting, which possesses high engineering application value.