An improved solid-state transfer switch controller for sensitive industrial loads

Voltage sags have become one of the most important power quality concerns in recent years. Voltage sags often cause under-voltage faults in various sensitive loads (like adjustable speed drives) and subsequently interrupt the manufacturing processes. Such interruptions result in severe losses for industries. As more and more utility companies provides dual power feeds to manufacturers who demand higher power reliability and power quality, the thyristor based solid-state transfer switch (STS) has become an viable solution to protect sensitive loads against voltage sags. This paper presents a controller with improved response time for detecting voltage sags in order to meet industrial requirements such as SEMI-F47.