An electric motor power system comprising: a converter-inverter that includes one or more converters (42, 44) including a group of semiconductor elements and one or more inverters (62, 64) including a group of semiconductor elements, the converter converting an AC power into a DC power, the inverter converting the DC power output by the converter into a three-phase AC power, the inverter outputting the three-phase AC power to a main motor (250, 252, 254, 256), and the converter-inverter including a DC circuit linking the converters and the inverters; and a respective cooler (204, 206) that cools the or each converter (42, 44) and the or each inverter (62, 64), characterized in that: the electric motor power system further comprises a storage battery which is connected to the DC circuit; and in regard of the or each converter (42, 44) and the or each inverter (62, 64) cooled by the respective cooler (204, 206), the group of semiconductor elements belonging to the converter (42, 44) is divided into a plurality of areas (210, 214) with the group of semiconductor elements belonging to the inverter (62, 64) provided therebetween, the converter (42, 44) charging the storage battery and the cooler (204, 206) cooling the converter when a power conversion operation by the inverter (62, 64) is stopped. a converter-inverter that includes one or more converters (42, 44) including a group of semiconductor elements and one or more inverters (62, 64) including a group of semiconductor elements, the converter converting an AC power into a DC power, the inverter converting the DC power output by the converter into a three-phase AC power, the inverter outputting the three-phase AC power to a main motor (250, 252, 254, 256), and the converter-inverter including a DC circuit linking the converters and the inverters; and a respective cooler (204, 206) that cools the or each converter (42, 44) and the or each inverter (62, 64), characterized in that: the electric motor power system further comprises a storage battery which is connected to the DC circuit; and in regard of the or each converter (42, 44) and the or each inverter (62, 64) cooled by the respective cooler (204, 206), the group of semiconductor elements belonging to the converter (42, 44) is divided into a plurality of areas (210, 214) with the group of semiconductor elements belonging to the inverter (62, 64) provided therebetween, the converter (42, 44) charging the storage battery and the cooler (204, 206) cooling the converter when a power conversion operation by the inverter (62, 64) is stopped. the electric motor power system further comprises a storage battery which is connected to the DC circuit; and in regard of the or each converter (42, 44) and the or each inverter (62, 64) cooled by the respective cooler (204, 206), the group of semiconductor elements belonging to the converter (42, 44) is divided into a plurality of areas (210, 214) with the group of semiconductor elements belonging to the inverter (62, 64) provided therebetween, the converter (42, 44) charging the storage battery and the cooler (204, 206) cooling the converter when a power conversion operation by the inverter (62, 64) is stopped.