Development On An Intelligent Solid Soft Starter Based On Variable Reactance Technique

Motor is a very important equipment in industry, agriculture and traffic. It is applied widely. Three phase Alternating Current asynchronous motor is almostly applied to all kinds of fields, because it has the specialty:low cost, high reliability, simple structure and convenient maintenance,etc. If the motor is started directly with full voltage, huge current and wallop will bring influence and damage to the motor itself, the load, the electric net and other equipment under the same net, with electric energy wasting.Intelligent Solid Soft Starter (ISSS) based on variable reactance technique is a kind of motor control device which can implement the soft-start, energy-saving and multi-protect function of the asynchronous motor. It is manufactured to realize saving energy for transmission of fan and pump equipment. In this thesis, soft starter equipment realized by thyristors power transform circuit is studied. To improve equipment performance, we apply variable reactance technique to AC motor soft starter study. The high voltage AC working winding of reactance is in series with motor winding, while low voltage control winding and thyristors groupware with intelligent controller constitute close loop circuit. We adopt thyristor phase control voltage-regulator mode to control low voltage winding, then control the reactance of high voltage winding, and then arrive at the goal-control the current and voltage of motor AC to realize motor soft starting.In this dissertation, development on ISSS based on variable reactance is studied and analyzed in depth. At first, deficiency of several traditional starting methods is expatiated. Then, combining with up-to-the-minute research fruit both at home and abroad, several motor soft start methods are compared. In succession, the design and blue print of ISSS are discussed. Furthermore the system design and work theory of ISSS are introduced. Then hardware circuit and electric connection design which takes S7-200 PLC as the main control unit is analyzed in detail. We adopt nine-point control theory to design software which is mostly fit for limiting current start mode.Then the simulation study shows the case is feasible. At last, system debugging is illuminated and experimental results are presented.The experiments show that ISSS can availably control shock current of starting, and the current is lower than 3 times rating current. Start time is about 3-80 seconds. The temperature of thyristor and transformer has no distinct rise. The equipment has advantage which can start motor continuously and quickly.