Discharging a bus of an electrically powered or hybrid vehicle

Abstract

The present disclosure relates to a sub-system for a vehicle comprising an electrical power bus () for distributing electrical power from an electrical energy storage means () to various different electrical components of the vehicle, such as a combined electric traction motor/generator (). The sub-system comprises means for disconnecting the electrical energy storage means () from the bus (), means () for measuring the potential difference between a rail of the bus of a first polarity and a chassis () of the vehicle, and means () for connecting the rail of the bus of the first polarity to the chassis () or a terminal of the electrical energy storage means of opposite polarity if the potential difference between the rail of the bus of the first polarity and the chassis is measured to be greater than a predetermined level, until the potential difference between the rail of the bus of the first polarity and the chassis is less than the predetermined level, then disconnecting the rail from the chassis or the terminal of the electrical energy storage means of opposite polarity, wherein the means () for connecting the rail of the bus to, then disconnecting the rail of the bus from, the chassis comprises the means () for measuring the potential difference between the rail of the bus and the chassis. This technique may be used to at least partially discharge a Y capacitance on the rail of the bus in question. The Y capacitance on any or all rails of the bus, of either polarity (positive or negative), may be discharged in this fashion, for example in the event of a collision of the vehicle, in order to render a high-voltage (HV) electrical supply sub-system () more safe. The present invention also provides a vehicle comprising such a sub-system and a method of reducing a potential difference between on the one hand, an electrical power bus () for distributing electrical power from an electrical energy storage means () of a vehicle and on the other, a chassis () of the vehicle to below a predetermined level.