A portable computer as an example of an electronic apparatus has a main unit, and a cover member placed on the upper surface of the main unit. The beams 4 are preferably made of steel and the floor 5a5b is preferably made of concrete, which may be precast units or may be concrete poured onto profiled steel decking. The semiconductor module includes multiple semiconductor devices. Each power cable assembly includes an impedance element that is added to the sensing circuit when the corresponding power cable assembly is coupled to the system, and once the detected voltage is beyond a predetermined threshold value, the control unit will ensure that the power cable assemblies are not energized by the power source. The surrounding wall is composed of plural partial walls having respective radiuses from a rotational axis of the rotor.