| 摘要 |
<P>PROBLEM TO BE SOLVED: To prolong the service life of a battery of a construction machine by suppressing a variance in power consumption at the time of start-up if a working environment changes. <P>SOLUTION: An inverter circuit 15 simultaneously and variably controls a target frequency and an input voltage to drive an electric motor 13 by the battery 14, and gives an approximation value of OHz as a target frequency F in the start-up of the electric motor 13, and continuously or stepwise increase the target frequency until the target frequency becomes a final target frequency maintaining the ratio of the target frequency F to an input voltage V. In a hydraulic excavator, load acting at the time of start changes corresponding to an external factor such as an atmospheric temperature, so that the inverter circuit 15, in which a PWM waveform adjusting section 22 is connected to a PWM control section 21, changes a time for increasing the target frequency by turning on/off a switching means 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
