Classification Variable Frequency High Torque Soft Start Controller

The adoption of soft starters can counteract the current impact to the power supply for induction motor starting. Soft starters decline only the electric voltage and do not decline the frequency, and make the starting torque turn small, therefore the soft starters be applicable only to the induction motors which drive the low starting torque machine such as blower fan and pump.This paper designed a soft starter adopting the discrete frequency method to start induction motors.It declines not only the electric voltage, but also makes the frequency lower at the same time, so starting torque turns more.This paper introduce current soft starters' the principle, starting modes, operatingmodes, stopping modes, reports of every kind of breakdown and development direction in future.The theory of discrete frequency method is analyzed , and is simulated. The results show that the application of discrete frequency method can not only reduce the current impact, but also increase the starting torque.The thesis analyses detailedly and designs the system's hardware units and software units. The soft starter employs high performances microprocessor 80C196KC as control core and its synchronous circuit can endure strong electromagnetism interference, and it has the intelligence to judge the phase order. It has three kinds starting modes: the slope voltage starting, the limiting current starting and the discrete frequency control starting. The experiment consequently prove that this soft starter operates well, has the simple construction, light weight, small volume,controllable starting current and starting time,smooth starting and can reduce the current impact for motor starting.Its discrete frequency control starting mode enable it to control the induction motors which drive Vated load during starting.