For externally-mounted motorized pulley, electric motor is removed out of the ordinary motorized pulley. And the pulley still with a retarding mechanism is often referred as a retarding drum. The motor is externally connected with the retarding drum to constitute an externally-mounted motorized pulley.

The externally-mounted motorized pulley is a kind of conveyor driving device between the traditional open-type drive mode from motor to reducer then to the drive pulley and the common motorized pulley driving mode. Because of the external motor, it enjoys good heat dissipation performance and easy repair and replacement. It takes about one-third less than the open-type drive in occupying space and manufacturing materials.

The externally-mounted motorized pulley is the product of the current industrial requirements. From the logic diagram, the main components are still connected in series, and at least one more drive shaft is needed. From the reliability, there is no increase in reliability. However, due to its good heat dissipation in the motor, convenience installation, maintenance and inspection of the motor, as well as its superiority in occupying space and manufacturing materials to the old open-type drive, the externally-mounted motorized pulley is usually used in high-power externally-mounted motorized pulley, and it is a suitable driving device in some high-power applications.