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Stator design eliminates cogging, hysteresis

Stator design eliminates cogging, hysteresis

When it comes to thinking outside the box, sometimes it's better to never have been in the box to begin with. That's the situation that led to the patented ThinGap TG3600 Series half-horsepower slotless, brushless dc servomotor, whose developers claim an efficiency of 89%, with controller, for the NEMA 23 motor.

Jerry Yankie, founder and CEO, and co-developer Greg Graham, were not "motor guys," says Yankie, but engineers who used motors, saw their failures, and said, "There has to be a better way." Yankie adds. "Basically we tried to maximize each element in the Lorenz Law of force-improving flux density, lowering resistance, and increasing current."

Key to the ThinGap configuration is the stator fabricated by stamping or etching a copper sheet. This is precisely rolled, and treated with polyamide resin and glass fiber, to form a freestanding stator without any iron components to cause cogging and hysteresis. The copper construction also gives low resistance for low I2 R heat losses (300 mohm, line-to-line). The stator fits within a thin cylindrical gap in the rotor between the inner permanent magnets and outer return-iron ring.

With no radial magnetic attractions present due to the all copper stator, the ThinGap is seeing wide use in fluid/air bearing motors. Its high temperature capability (160C) without the use of exotic material is also useful in medical devices subject to sterilization. Contact: Jerry Yankie, ThinGap Motor Technologies 2140 Eastman Ave., #112, Ventura, CA 93003 Tel (805) 477-9741; Fax (805) 477-7535; or enter 510 at

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