Inverter Motor Drive Ride-Through Schemes for Continuous Process Applications

In continuous process manufacturing, process downtime resulting from electric variable speed drive equipment shutdown due to momentary power line dips or outages can incur heavy cost penalties brought about by loss of product or long process-restart times. In the case of ac adjustable speed inverter drives, the continuous process industries involved in this problem are presently synthetic textile manufacturing and thin-film products processing industries. Existing momentary voltage dip ride-through techniques as applied to adjustable speed inverter motor drives are reviewed with reference to the requirements of continuous process applications. Configurations considered are the variable voltage, input, the pulsewidth modulated, and the current source inverter types. Emphasis is placed on electrical ridethrough techniques as opposed to electromechanical techniques. The advantages and disadvantages of each method are discussed, and basic design and application considerations are outlined.