Kobelco Construction Machinery Co., Ltd.

Sinfonia Technology Co., Ltd.

Hiroyuki Suminaga

Yusuke Kamimura

Hideaki Moriya

Takeshi Tomizaki

Akira Nakazumi

An object of the present invention is to provide an inverter device for driving an electric motor, which allows control stability and efficiency to be ensured over a wide region of the speed of the electric motor. The inverter device includes a rotational-speed detection section which detects a rotational speed of the electric motor, a carrier-frequency calculation section which calculates a carrier frequency on the basis of the detected rotational speed, and a carrier-frequency switching section which switches, on the basis of the calculated carrier frequency, the carrier frequency used for performing PWM control on the electric motor. The carrier-frequency calculation section calculates, as the carrier frequency, a frequency increased with an increase in the electric-motor rotational speed detected by the rotational-speed detection section.

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Tokyo, Japan

Hiroyuki Suminaga