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Designer's Corner

By John Lewis, Regional Editor -- Design News, December 7, 1998

WE ARE HERE!!!Slotless stator

Generally, brushless motors provide high speed and fast acceleration, generate less audible noise and electromagnetic interference, and require low maintenance. In contrast, brush-commutated motors afford smooth operation and greater economy. A slotless stator design challenges conventional wisdom and allows designers to specify brushless motors that combine the traditional advantages of both types.

Because traditional brushless motors wind copper wires through slots in a laminated silicon-steel core, magnets passing by the lamination shoes have a greater attraction to the iron at the top of the laminations than to the air gap between the shoes. This uneven magnetic pull causes cogging, which increases motor vibration and noise.

In a slotless, brushless design, the motor's copper wires are wound against the laminations and held with adhesive. This design yields smooth rotation and virtually eliminates cogging.

Richard Green, Pittman (P),
343 Godshall Dr.
Harleysville, PA 19348-0003
(215) 256-6601.

WE ARE HERE!!!Illuminating balloon

Enclosing a 1- or 2-kW halogen lamp, the self-inflating "Sirocco" balloon illuminates 1,400 sq m with multi-directional, reduced-glare lighting. Its triple-layer, high-tensile-strength polyester skin, supplied by Porcher-Marine (Lyon, France), combines the necessary light transmission, fire-resistance, and temperature characteristics.

Good for mobile construction sites and rescue operations, Sirocco inflates in 45 sec, incorporates a blower and pressure sensor, measures 1.1 X 0.8m, and resists winds to 100 km/hr.

Todd Wimett,
Airstar America (E),
13370 San Fernando Rd.,Unit 106,
Los Angeles, CA 90065; (800) 217-9001.

WE ARE HERE!!!Direct-drive motor

Servo systems typically contain gearboxes, belts, pulleys, and power-transmission shafts--often with right-angle turns. Not all applications require such complexity, however.

A direct-drive solution, based on a line of new permanent magnet brushless servo motors, simplifies servo systems. Three design features explain how:

Economical ferrite magnets are oriented to provide high flux density.

• A segmented rotor facilitates manufacturing.

• Many poles and armature slots reduce torque harmonics at slow speeds.

In addition, the motor's armature is encapsulated in thermally conductive material, allowing a smaller volume.

Monte Swinford
Vickers Electronic Systems (P)
1151 W. Mason-Morrow Rd.
Lebanon, OH 45036
(513) 494-5654.

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