A traction system of a railway car comprising an AC generator means driven by an engine, a first power conversion means connected to the AC generator means and capable of mutually converting power between AC power and DC power, an AC traction motor, a second power conversion means connected to the AC traction motor and capable of mutually converting power between AC power and DC power, and a storage system connected to a DC-side of the two power conversion means, characterised in that the traction system of a railway car further comprises two selectors (9a, 9b) corresponding to the first and second power conversion means for mutually switching an AC-side device of the two power conversion means, and three line breakers (10a, 10b, 10c) for disconnecting the circuit between the first power conversion means, the second power conversion means and the storage system, wherein: in case failure occurs to the second power conversion means and the amount of charge of the storage system is at an insufficient state, the system is configured to disconnect one of the three line breakers corresponding to the second power conversion means, and to connect the first power conversion means and the AC generator means by the selector of the first conversion means, in case failure occurs to the second power conversion means and the amount of charge of the storage system is at a sufficient state, the system is configured to disconnect one of the three line breakers corresponding to the second power conversion means, and to connect the first power conversion means and the AC traction motor by the selector of the first conversion means, in case failure occurs to the first power conversion means and the amount of charge of the storage system is at an insufficient state, the system is configured to disconnect another line breaker corresponding to the first power conversion means, and to connect the second power conversion means and the AC generator means by the selector of the second conversion means, and in case failure occurs to the first power conversion means and the amount of charge of the storage system is at a sufficient state, the system is configured to disconnect another line breaker corresponding to the first power conversion means, and to connect the second power conversion means and the AC traction motor by the selector of the second conversion means; such that the system is able to store energy in the storage system via a healthy-operating power conversion means when either one of the two power conversion means fails, and to drive the AC traction motor using the stored energy. in case failure occurs to the second power conversion means and the amount of charge of the storage system is at an insufficient state, the system is configured to disconnect one of the three line breakers corresponding to the second power conversion means, and to connect the first power conversion means and the AC generator means by the selector of the first conversion means, in case failure occurs to the second power conversion means and the amount of charge of the storage system is at a sufficient state, the system is configured to disconnect one of the three line breakers corresponding to the second power conversion means, and to connect the first power conversion means and the AC traction motor by the selector of the first conversion means, in case failure occurs to the first power conversion means and the amount of charge of the storage system is at an insufficient state, the system is configured to disconnect another line breaker corresponding to the first power conversion means, and to connect the second power conversion means and the AC generator means by the selector of the second conversion means, and in case failure occurs to the first power conversion means and the amount of charge of the storage system is at a sufficient state, the system is configured to disconnect another line breaker corresponding to the first power conversion means, and to connect the second power conversion means and the AC traction motor by the selector of the second conversion means; such that the system is able to store energy in the storage system via a healthy-operating power conversion means when either one of the two power conversion means fails, and to drive the AC traction motor using the stored energy.