Abstract: A main power supply having a large capacity and a backup power supply having a small capacity are switchable by a power supply switching determination unit in a system. A motor control device drives a motor by the main power supply or the backup power supply. A drive control unit outputs a drive signal, calculated by feedback control of the current detection value with respect to the current command value, to an inverter circuit. When the power supply switching determination unit switches from the main power supply to the backup power supply, the drive control unit moves from a normal control using the main power supply to a backup control that restricts an electric power consumption and prevents the backup power supply from stopping.

Abstract: A battery pack and a method of diagnosing a failure of an overcurrent detection circuit are provided to diagnosing the overcurrent detection circuit so as to maintain the overcurrent detection circuit in a safe state. A detection signal output from a current detection element connected to an output side of a battery unit is compared with a threshold value. An overcurrent is detected when the detection signal indicates an overcurrent value exceeding the threshold value. In the method, a failure of the overcurrent detection circuit is detected by inputting an overcurrent diagnostic signal to the overcurrent detection circuit.

Abstract: A file management system according to the present invention includes a server apparatus and a client apparatus. The server apparatus includes a file server, a file information database, an authority database, and a server-side communication section for sending a file and access authority information to the client apparatus. The client apparatus includes a client-side communication section, an application program for making a user utilize the file received by the client-side communication section, and an application controlling section for restricting a function of an application capable of being utilized by the user based on the access authority information received by the client-side communication section when the user utilizes the file received by the client-side communication section.