Makita Corporation

Masayuki Okamura

Itsuku Kato

Dai Suzuki

Kazuya Okuma

An electric work machine includes a first and second motors; a first and second switches disposed on corresponding current conduction path from a direct-current power source to each motor; a first and second carrier frequency setting devices; and a controller. The first and second carrier frequency setting devices respectively set a first and second carrier frequencies of a time when PWM controlling an electric power supply to the first and second motors. The first and second carrier frequencies are different from each other. The controller drives the first switch or the second switch by using a PWM signal generated at the first or second carrier frequency and PWM controls an electric power supply to the first or second motor.

Electric work machine

An electric working machine in one aspect of the present disclosure calculates an estimated heat value based on an electric current value and a parameter. The estimated heat value corresponds to an estimated heat generation amount of a motor. The electric current value corresponds to a magnitude of an electric current delivered from a power source to the motor. The electric work machine varies the parameter based on a load time. The load time corresponds to a time period during which a first load is continuously imposed on the motor. The first load has a specified magnitude or more. The electric work machine performs a protective operation for over temperature protection of the motor based on the estimated heat value having reached a heat threshold.

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Anjo, Japan

Masayuki Okamura