Patent ID: 8252471

Claim:
A fuel cell system, comprising: a fuel cell configured to generate electric power through electrochemical reactions of a fuel gas and an oxidizing gas; a reservoir configured to store the fuel gas; a supply piping arranged to connect the fuel cell with the reservoir; a regulator configured to regulate a supply pressure of the fuel gas from the reservoir to the fuel cell; a circulation pump configured to recirculate a fuel off-gas discharged from the fuel cell to the supply piping; a measuring instrument configured to measure a pump temperature representing temperature of the circulation pump; a restrictor provided on the circulation pump and configured to stop operation of the circulation pump when the pump temperature exceeds a second temperature, which is set to be higher than a preset first temperature used for determining a changeover of control from recycling hydrogen with the circulation pump to increasing a concentration of the fuel gas; and a controller configured to, when the pump temperature does not exceed a third temperature that is set to be lower than the second temperature but higher than the first temperature, reduce or maintain a rotation speed of the circulation pump and control the regulator to perform a stoichiometric ratio control of increasing the supply pressure of the fuel gas from the reservoir to the fuel cell, and when the pump temperature exceeds the third temperature, to stop operation of the circulation pump and control the regulator to perform the stoichiometric ration control of increasing the supply pressure of the fuel gas from the reservoir to the fuel cell, wherein the first and second temperatures are set such that a temperature difference between the first and second temperatures decreases with a decrease in required output for the fuel cell.