Research Of Intelligent Grid For Variable Frequency Soft Starter In Synchronous Motor

With the development of modern industry, synchronous motor is more and more widelyapplied in high-power industrial sites because of its overload capacity, high efficiency and theability of improving the power factor of power grid. For high-power AC motor, the startingcurrent is five to seven times as big as the rated current and will remain for more than10seconds.This inrush current on the one hand could cause a decline in power grid voltage and relayprotection misoperation, interfere with the normal operation of other devices on the same busand lead to equipment downtime when serious; On the other hand could reduce the service life ofmotor and the high voltage switch.for more than6000KW high-power synchronous motor starting, variable frequency softstart is the optimal scheme of soft start performance in the methods of limiting the startingcurrent of the motor.using the method of variable frequency soft start,if high-power synchronousmotor adopts the high-power inverter starting and drives load operation, the economic costs willbe high,which isn’t suitable for industrial production.If using the low-power inverter starting, thecost will be significantly reduced, but the inverter load ability is limited,which can start withno-load,but can not completely drag load after synchronous motor starts. This need to switch topower frequency at the end of variable frequency soft starter,so the article will elaborate thesmart grid process of variable frequency soft starter in detail.First, this paper introduces the basic structure and characteristics of synchronous motor;Then,it expounds the variable frequency speed regulation principle of synchronous motor, thevariable frequency speed regulation system and the excitation system of synchronous motor;Finally, based on the above theory,it designs a frequency soft start smart grid system.Text content is divided into six chapters: the first chapter is introduction; The secondchapter is synchronous motor brush excitation system; The third chapter is the principle ofAC-DC-AC variable frequency and variable frequency speed regulation system; The fourthchapter is sinusoidal pulse width modulation technique; The fifth chapter is the implementationprocess of synchronous motor variable frequency soft start smart grid; The sixth chapter issummarizes and prospect of this article.