COX Torque-Limiting Permanent Magnet Coupling .

COX is a limited-moment permanent magnet coupler (developed by Jiaohua in 2012): torque is transmitted across an air gap between a copper conductor rotor on the motor shaft and a permanent magnet rotor on the reducer side, with no mechanical connection. At start-up the gap opens from 5 to 8 mm so the motor accelerates almost unloaded; if the load jams, the gap opens to 35 mm and torque transmission stops, and the coupler returns to operation by itself once the cause is removed. Slip 1–4 %, no oil, bearings or power supply. 16 sizes, 11–710 kW at 1,500 rpm.