AC Synchronous Motors
From Hansen Corporation

Synchronous motors are inherently constant-speed motors and they operate in absolute synchronism with line frequency. Hansen offers both Hysteresis and Permanent Magnet synchronous motors (PM Synchronous Motors) to meet your exact needs. The hysteresis design, Hansen's famous Genuine Synchron®, is extremely quiet and smooth in operation and has very low cogging torque, ideal for back-driving. Because it is light in torque, it is always attached to a Hansen ultra precision gearbox.

Synchron® 600: AC Synchronous Timing Motor - Round (A & D-Mount) Gearbox

AC timing motors in a round case configuration with either two-hole (Model-D) or four-hole (Model-A) mounting plates. Output speeds from the integral gearhead can be chosen from a range of 0.8 rpm to 360 rpm.
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Synchron® 600: AC Synchronous Timing Motor - Shallow Pear (C-Mount) Gearbox

AC timing motor with precise synchronous speeds ranging from 0.50 revolution per hour to 360 rpm. Options include a 1-way clutch so that a reset function can be implemented or with a 2-way clutch for gear train protection from excessive loads at output speeds below 6 rpm.
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Synchron® 600: AC Synchronous Timing Motor - Deep Pear (K-Mount) Gearbox

Synchron 600 Series, K mount, AC timing motors offer a deeper gearbox which can be geared down to a speed of 1 revolution per week.
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