HPAC Engineering, Dec. 2016, by Bill Lampkin.
http://hpac.com/iaq-ventilation/selecting-actuators-industrial-hvacprocess-dampers

"If it is to accomplish its intended purpose, any damper installed in a HVAC system must be equipped with an appropriate actuator. The selection of an actuator for a specific damper requires consideration of a number of factors. This article examines the actuator-selection process. (Note: While damper actuators often go by other names, such as damper motors, damper operators, and motor packs, “damper actuator” is the appropriate terminology.)"