Energy Saving on the Latest AC Drives System

Abstract

There are so many numbers and capacity of motors and drives applied to paper making machinery in pulp and paper industries. The loads such as fans, pumps, and blowers usually require the constant speed rotation of motors conventionally and have been driven by adjustable speed drives by inverters for energy savings recently. On the other hand the loads such as paper machines, winders and coaters usually require the adjustable speed rotation of motors and drives, driven by DC motors and drives, conventionally, and have been driven by AC drives for better maintainability, not for energy savings.
This article describes the energy savings effect on the latter load (paper machines, winders and coaters), which conventionally require adjustable speed rotation of motors, comparing AC drives with DC drives.
The AC drives for a winder are highly precise digital vector controlled PWM inverters, which have a common DC converter for an unwinder and drums, and the motors are rigid and simple structured squirrel cage induction motors. The inverter for an unwinder is tension regulated and the inverter for a drum is speed regulated. When a winder is driven by AC drives whose converter is common for inverters, the power for tension is fed from the inverter for drum and powered back from the inverter for unwinder without power feeding from power source. When a winder is driven by DC drives, the power for tension is fed from the converter for drum and powered backed from the converter for unwinder. DC drive feeds the field power of DC motors and generates loss. And the efficiency of the induction motor is higher than that of DC motor. Total efficiency of AC drives is higher than that of DC drives. The example figures are shown.