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`Film coil` motors promise many attractions

01 July, 2001

`Film coil` motors promise many attractions

A Korean company has developed a technology for creating motor "coils" on flexible printed circuits as an alternative to conventional windings. Among the attractions that Seoul-based EMbest claims for this process are low manufacturing costs, light weight, simple structures, low inductances, high efficiencies, and easy maintenance.

The company suggest that its "film coil" technology could be applied to a wide range of cylindrical and disk motors from small machines used in applications such as computer peripherals, through to motors used to power golfcarts and industrial equipment.

The process involves etching patterns in copper films on both sides of an insulating layer. By connecting the two sides via holes through this layer, dense coil patterns can be created.

One of the first products to use the technology is a family of coreless motors Shown above), that range in size from 29mm-diameter, 40mm-long models that produce 10mNm at 2,900 rpm, to 82mm-diameter, 125mm-long versions, capable of delivering 600mNm at 2,000 rpm.

EMbest points out that conventionally wound coreless motors are not widely used because of their high price. It claims that by doing away with the iron core, it can produce a low-cost machine with low inductance, low noise levels, a long life, a high efficiency (because there no core loss), a high output for its size, no cogging, and linear load-speed and load-current relationships. And because the rotor carries only the armature coils and a commutator, its inertia is small, allowing rapid acceleration and deceleration.

EMbest has also developed brushless disk motors based on the film coil technology. The potential attractions are similar to those of the cylindrical motors. The company claims that unlike existing printed circuit motors, its coreless disk motors can have many layers of coils. The coils remain stationary while disk-shaped permanent magnets rotate. The disk motors range from 120mm-diameter, 34mm-long models which deliver 80mNm at 1,200 rpm, to 152mm-diameter, 54mm-long versions producing 500mNm at 4,000 rpm.

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