Murata Manufacturing Co Ltd announced that its high-power, large laminated ceramic capacitor is used in a plug-in hybrid electric scooter.
The ceramic capacitor was exhibited at AT International 2008, which took place from July 23 to 25, 2008, at Makuhari Messe in Chiba Prefecture, Japan. The scooter was released from Vectrix Corp in summer 2007 and is sold at US$9,395 in North America.
Four units of Murata capacitors are installed on a circuit board (manufactured by Perker Hannifin Corp), which is designed for the smoothing in the inverter. The capacitors are used to reduce the surge generated by IGBT (insulated gate bipolar transistor).
In an application described as above, "the only solution thus far has been to use a film capacitor or an aluminum electrolytic capacitor," a demonstrator from Murata said.
"But these types of capacitors are faced with the problem of degradation by heat, because the film used in a film capacitor is an organic material, and an Al electrolytic capacitor requires an organic substance to seal the electrolyte," the demonstrator added. "Our ceramic capacitor is entirely made of inorganic materials, and thus has a high heat resistance."
In addition, the ceramic capacitor has an advantage in that it can reduce the footprint of the smoothing circuit. Murata's ceramic capacitor reportedly has a capacity per unit volume of 2.4μF/cm3, whereas the capacity per unit volume of a film capacitor is 1.2μF/cm3, and that of an Al electrolytic capacitor is 1.89μF/cm3.
Another characteristic of the ceramic capacitor is that it has a high allowable ripple current of 1.56A/cm3. This is an order of magnitude higher than that of a film capacitor, and two orders of magnitude higher than that of an Al electrolytic capacitor.
"At the present, it is true that the ceramic capacitor is more expensive than film and Al electrolytic capacitors, but we hope to improve the economies of scale in production by taking advantage of its higher heat resistance and smaller dimensions," the demonstrator said, explaining about the most important aspect, the price.
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