Trends and developments in feedback devices for adjustable speed drives

Feedback tachometer generators have been used in the pulp and paper industry for decades. The author briefly traces historical trends and developments in an effort to determine the needs of the industry today. The electrical evolution of feedback tachometer generators from inaccurate analog devices to precise digital devices has improved drive system accuracy and stability. Changes have also occurred in the mechanical configurations to improve reliability. The latest trend is toward higher resolution of up to 2048 pulses per revolution and mechanical designs that eliminate failure prone components. Six case histories are included that show how today's designs solve problems, improve performance, and increase reliability. Included in these case histories are modular designs and shaft mounted designs.<>