Improved hard pre-charge for parallel inverters

An improved hard pre charge in a traction system for railway comprising at least two different motors, each motor being controlled by means of a least one of two inverters which are connected in parallel to a common power line that supplies a DC power signal by means of a respective DC-link, an isolation switch being provided for each of said two inverters, which isolates the corresponding inverter from said power line, each inverter being further connected to the common power line by a filter capacitor bank and means for pre-charging said capacitor banks, which pre-charging means include a crow bar resistor and an automatic power switch which transfer the DC power signal to said crow bar resistor when voltage exceeds a predetermined threshold. In order to utilize the energy dissipated by the protection resistor, the invention provides means for alternately closing the isolation switches of one of the two inverters and a connection diverting the power signal from the crow bar resistor of the inverter connected to the power signal supply line by the said automatic power switch to the filter capacitor bank of the other inverter which is isolated from the power signal supply line.