Rail vehicle comprising: - a polyphase motor which is provided with an electrical connection terminal for each phase of the motor and a rotor which has permanent magnets and which is capable of rotatably driving the driving wheels of the rail vehicle, - a polyphase inverter which is capable of supplying a polyphase supply voltage of the motor, this inverter being provided with a connection terminal for each phase, and - at least one controllable contactor for each phase of the motor, this contactor being provided with at least two electrodes which are electrically connected, respectively, to a respective terminal of the inverter and to a respective terminal of the motor, these two electrodes being able to be moved between a non-conducting state in which they electrically isolate from each other the terminals of the inverter and the motor to which they are connected and a conducting state in which they electrically connect these two terminals, the two electrodes being separated by an inter-electrode spacing D in the non-conducting state, characterised in that each contactor comprises a bulb inside which there is a pressure P in the non-conducting state, the electrodes being placed inside this bulb, and the product of the pressure P multiplied by the inter-electrode spacing D is to the left of the minimum of the Paschen curve, and in that the rail vehicle comprises a control unit which is capable of controlling the opening of the contactors in the presence of an asymmetrical short-circuit, an asymmetrical short-circuit being defined as a situation in which the current in one of the phases has both a continuous component and a periodic fundamental component which is not equal to zero, the amplitude of the continuous component being strictly greater than the amplitude of the periodic fundamental component so that the current is never cancelled in this phase. - a polyphase motor which is provided with an electrical connection terminal for each phase of the motor and a rotor which has permanent magnets and which is capable of rotatably driving the driving wheels of the rail vehicle, - a polyphase inverter which is capable of supplying a polyphase supply voltage of the motor, this inverter being provided with a connection terminal for each phase, and - at least one controllable contactor for each phase of the motor, this contactor being provided with at least two electrodes which are electrically connected, respectively, to a respective terminal of the inverter and to a respective terminal of the motor, these two electrodes being able to be moved between a non-conducting state in which they electrically isolate from each other the terminals of the inverter and the motor to which they are connected and a conducting state in which they electrically connect these two terminals, the two electrodes being separated by an inter-electrode spacing D in the non-conducting state, characterised in that each contactor comprises a bulb inside which there is a pressure P in the non-conducting state, the electrodes being placed inside this bulb, and the product of the pressure P multiplied by the inter-electrode spacing D is to the left of the minimum of the Paschen curve,