PORTLAND, Ore. Inductors smooth current flow in voltage conversion applications, but add significant bulk and cost, especially to high power applications like hybrid vehicles. Now a shaped-foil inductor design is offering loss reductions as high as 50 percent compared to conventional inductors.
The shaped-foil design was invented at Dartmouth College (Hanover, N.H.) and has been licensed to West Coast Magnetics (Stockton, Calif.).
"What this really means is that you can now use a smaller inductor, and thus lower costs of, for instance, in hybrid vehicles and other high power applications like wind and solar power generators," said Weyman Lundquist, president of West Coast Magnetics.
For now, the patented design has limited use. For instance, it is limited to inductors that carry a DC current and only works if the core has a gap. It is also limited to applications with sufficiently high current to benefit from a foil winding. Nevertheless, the market for this type of inductor is huge, according to West Coast Magnetics.
The patented design used a unique shaping process to pack more copper into a smaller area than conventional inductor designs. High-power applications often have to use bulky litz wire wound inductors. By shaping a foil inductor in a proprietary pattern, the new design reduces the size of a foil inductor while providing the benefits of a wire-wound design.
"The foil is cut and shaped in a patented pattern that enabled the eddy losses to be minimized, so the results is very similar to what you find in a litz wire wound inductor," said Lundquist. "You want to maximize the amount of copper in that available area to offer lower DC resistance, but it also offers the low AC resistance of a [multistrand] litz wire wound inductor."
Lundquist predicted the shaped-foil inductor will be useful in high power conversion applications such as hybrid vehicles and other applications relying on conversion and conditioning of energy at high power levels.
Along with hybrid vehicles and energy production, the design will also work with integrated gate bipolar technology, which is used to control high power electronic devices designed to operate at current levels at 100 amps or higher and at frequencies above 10 KHz, Lundquist said.
West Coast Magnetics also hopes the shaped-foil inductor can be reduced in size for use in lower power applications, including PCs and handheld devices.