| CPC F04D 25/06 (2013.01) [F04D 27/0215 (2013.01); F04D 27/0253 (2013.01); H01M 8/04111 (2013.01)] | 19 Claims |

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1. A method of operating a multi-stage air compression system (1) comprising an electrically driven first compressor (1.1) and a second compressor (1.2) driven by a turbine (2), wherein the compressors (1.1, 1.2) are arranged in a supply air path (3) and the turbine (2) is arranged in an exhaust air path (4) of an air system for supplying air to a fuel cell stack (5),
wherein, when the air compression system (1) is started, air compressed by the first compressor (1.1) is supplied to the fuel cell stack (5) via a bypass (6) to bypass the second compressor (1.2) and the second compressor (1.2) is connected to surrounding environment on both inlet and outlet sides via at least one valve (7, 8) and/or a throttle valve (9).
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