... 1,Simple structure, small size, light weight, only half weight of clutch motor and DC motor at ... and high torque.4,This motor is no carbon brush design, no sparks security, long-term use without ... the friction clutch to the sewing machine, efficiency is only around 70%.Therefore, the real power for ... the sewing machine utilization rate is only about 50%. The energy-saving motors is a DC servo motor, ...