To control the temperature in a device during the operation of an electronic computer and a sharp rise or lowering in temperature in temporary stop or complete stop, and to achieve energy saving during operation and component defect reduction in temporary stop and complete stop and the reduction of the possibility of an defect in restart, in a system in which a plurality of power supply devices or electronic computers loaded on an electronic computer are loaded in parallel.

A plurality of temperature sensors are arranged in the device of an electronic computer, and the rotation control of a cooling fan is performed by performing temperature measurement by a temperature sensor arranged in the device during an operation from start, and when the electronic computer stops, the cooling fan does not stop, and the rotation control of the cooling fan is performed by the temperature measurement of the temperature sensor. Also, the cooling fan at an exhaust side is rotated backward, and the temperature in the device is gently dropped to gradually drop the temperature in the electronic computer device.