Inductive Power Transfer System for an Excavator by considering Large Load Fluctuation

In this study, an inductive power transfer system (IPT) was designed and developed for an excavator, which will be operated under high air pressure. In the conventional excavator systems, power is supplied through trolley wires. The contact between the trolley wires and a pantagraph may be a reason of fire due to a spark because the excavator works under high air pressure. In the proposed system, a series resonance capacitor on a primary side and a parallel resonance capacitor in a secondary side is used to cancel out the leakage inductance. By using the series-parallel compensation, the load voltage is ideally constant regardless of load fluctuation. However, the constant-voltage characteristic may degrades when a winding resistance and an error of the resonant parameter cannot be ignored. Thus, the resonant parameters must be designed considering the error. This paper proposes the design method of the resonant parameter with the voltage ratio maps considering the error of the parameter including the winding resistance. The experimental results confirmed that the voltage fluctuation is smaller than 4.3% with a developed 15-kW IPT system. Furthermore, the constant-voltage characteristic is maintained even when the output power of an induction motor changes from 5 to 15 kW and vice versa.